RBI FUTERA XLF Series, FUTERA III Series, FUTERA FUSION Series, HeatNet V3 Control Manual

V3HN-I0M-3

82-0400

®

HeatNet

V3

Control Manual

Control adjustment and operation instructions
for firmware versions Version 3.x

This instruction manual applies only to version 3.x
firmware on version 3.x control boards. Current
firmware is backwards compatible with version 2.x
boards, but some current features may not be
available. To replace firmware on an existing
boiler, contact the factory or website

http://www.rbiwaterheaters.com to obtain the

original firmware file or for assistance in applying
current firmware to an older version control board.

Also read and follow:

Futera III Boiler manual or

Futera Fusion Boiler manual or

Futera XLF Boiler manual

This manual is intended only for use by a qualified heating installer/technician. Read and follow this manual, all
supplements and related instructional information provided with the boiler. Install, start and service the boiler only
in the sequence and methods given in these instructions. Failure to do so can result in severe personal injury,
death or substantial property damage.

Do not use the boiler during construction. Construction dust and particulate, particularly drywall dust, will cause
contamination of the burner, resulting in possible severe personal injury, death or substantial property damage.
The boiler can only be operated with a dust-free air supply. Follow the instruction manual procedures to duct air to
the boiler air intake. If the boiler has been contaminated by operation with contaminated air, follow the instruction
manual guidelines to clean, repair or replace the boiler if necessary.

Affix these instructions near to the boiler. Instruct the building owner to retain the instructions for future use by a

qua hnician, and to follow all guidelines in the User’s Information Manual.

Copyright 2019 Mestek, Inc.

Information contained in this publication regarding device applications and the like
is provided only for your convenience and may be superseded by updates. It is your
responsibility to ensure that your application meets with your specifications.

RBI MAKES NO REPRESENTATIONS OR WARRANTIES OF ANY KIND

WHETHER EXPRESS OR IMPLIED, WRITTEN OR ORAL, STATUTORY OR
OTHERWISE, RELATED TO THE INFORMATION, INCLUDING BUT NOT
LIMITED TO ITS CONDITION, QUALITY, PERFORMANCE,
MERCHANTABILITY OR FITNESS FOR PURPOSE.

http://www.rbiwaterheaters.com/

The RBI name and logo, Mestek name and logo, Futera, HeatNet, and H­Net name and logo are registered trademarks of Mestek, Incorporated in the
U.S.A. and other countries.

BACnet is a registered trademark of ASHRAE. LonWorks is a registered
trademark of Echelon Corporation. All trademarks mentioned herein are
property of their respective companies.

© 2019, Mestek Technology Incorporated, Printed in the U.S.A., All Rights
Reserved.

TABLE OF CONTENTS

Page 3

Table of Contents

TABLE OF CONTENTS .............................................................................................................................. 3

Introduction ................................................................................................................................................ 5

THE FUTERA III/FUSION-SERIES V3 HEATNET CONTROL ....................................................................................................................... 5

Features & Specifications ......................................................................................................................... 7

STANDARD FEATURES OVERVIEW ........................................................................................................................................................ 7

Specifications ................................................................................................ ............................................ 9

Components & Accessories ................................................................ ................................................... 10

Setup & Operation ................................................................................................................................... 11

BASIC MULTI BOILER SYSTEM OPERATION................................ ................................................................ ................................ .......... 11

MIXED BOILER TYPES USING PRIORITY SETS ..................................................................................................................................... 12

MIXED BOILER SYSTEM OPERATION ................................................................................................................................................... 12

START/STOP PRIORITY CONDITIONS ................................................................................................ .................................................. 14

SELECTING MIXED BOILERS .............................................................................................................................................................. 15

MIXED SYSTEM TYPE 1: HIGH SYSTEM TURNDOWN ............................................................................................................................ 15

MIXED SYSTEM TYPE 2: CONDENSING / NON-CONDENSING .................................................................................................................. 18

Heating Control Methods ........................................................................................................................ 22

HEATING METHOD 1 ......................................................................................................................................................................... 22

HEATING METHOD 2 ......................................................................................................................................................................... 22

HEATING METHOD 3 ......................................................................................................................................................................... 22

HEATING METHOD 4 ......................................................................................................................................................................... 22

HEATING METHOD 5 ......................................................................................................................................................................... 22

OPERATING LIMIT ............................................................................................................................................................................. 22

INPUT PRIORITIES ............................................................................................................................................................................ 22

HEATING METHOD 1 HEAT DEMAND .............................................................................................................................................. 23

HEATING METHOD 2 STAGE CONTROL T1-T2 ................................................................................................................................... 23

HEATING METHOD 3 4-20MA CONTROL ............................................................................................................................................. 24

HEATING METHOD 4 AA INPUT .......................................................................................................................................................... 24

HEATING METHOD 5 MODBUS COMMUNICATIONS .............................................................................................................................. 24

BASE LOADING, RELAY CONTROL ...................................................................................................................................................... 25

SETTING UP BASE LOADING ............................................................................................................................................................... 28

Domestic Hot Water Methods ................................................................................................................. 28

DHW MAXIMUM RUNTIME ................................................................................................................................................................. 29

DHW METHOD 1: DHW HEATING ONLY USING A DHW MASTER AND MEMBER BOILER(S) EMPLOYING H-NET .................................. 30

DHW METHOD 2: FAILSAFE COMBINATION DHW AND SPACE HEATING WITH A MASTER BOILER AND MEMBER BOILERS UTILIZING VALVES

(MASTER TYPE: COMBINATION) ...................................................................................................................................................... 34

DHW METHOD 2: FAILSAFE COMBINATION DHW AND SPACE HEATING WITH A MASTER BOILER AND MEMBER BOILERS UTILIZING PUMPS

(MASTER TYPE: COMBINATION) ...................................................................................................................................................... 36

DHW METHOD 3: DHW HEATING ONLY, USING A HEADER SENSOR INPUT ........................................................................................... 40

DHW METHOD 4A: SPACE HEATING WITH DHW OVERRIDE OF SETPOINT ON MASTER, USING AN AQUASTAT ......................................... 43

DHW METHOD 4B: SPACE HEATING WITH DHW OVERRIDE OF SETPOINT ON MASTER, USING A DHW 10K TANK SENSOR ..................... 46

DHW METHOD 5A: LOCAL DHW TANK HEATING USING A 10K TANK SENSOR. ....................................................................................... 49

DHW METHOD 5B: LOCAL DHW TANK HEATING USING A THERMOSTAT & HYBRID SENSOR. ................................................................... 53

DHW METHOD 6: DHW USING DIRECT CONTROL (NOT PREFERRED) ................................................................................................. 55

Using the 4-20mA input (OPTIONAL) ..................................................................................................... 55

SETPOINT PRIORITIES ....................................................................................................................................................................... 57

Circulator Pump Options ........................................................................................................................ 57

Local Pump Option ................................................................ ................................................................ .. 59

TABLE OF CONTENTS HeatNet Control V3

Page 4

Auxiliary Function Options ................................................................................................ ..................... 59

Outdoor Reset ......................................................................................................................................... 60

Sensors .................................................................................................................................................... 60

Stack Temperature .................................................................................................................................. 60

Security .................................................................................................................................................... 61

Save/Restore Configuration Settings ..................................................................................................... 61

USB Features ........................................................................................................................................... 61

Saving/Restoring Settings ...................................................................................................................... 61

Diagnostics .............................................................................................................................................. 61

Communications ..................................................................................................................................... 62

Failsafe Modes ......................................................................................................................................... 62

FAILSAFE REQUIREMENTS: ................................................................................................................................................................ 62

Category 1 Venting .................................................................................................................................. 63

Limited Flow Boiler Control Options ...................................................................................................... 63

HeatNet Online ......................................................................................................................................... 65

Wiring Connections ................................................................................................................................. 66

* Status Information ................................................................................................................................ 78

STATUS INFORMATION SCREENS ........................................................................................................................................................ 78

Status Screen Fault Display .................................................................................................................... 80

Calibration ................................................................................................................................................ 83

Log Entry.................................................................................................................................................. 84

Line 4 Log Entries: .................................................................................................................................. 85

Default Settings & Menu Item Descriptions — SETUP .......................................................................... 88

Default Settings & Menu Item Descriptions — ADVANCED SETUP ..................................................... 94

MODBUS Communications ................................................................................................................... 101

Troubleshooting .................................................................................................................................... 112

Futera III/Fusion-Series HeatNet Control Run Screen ......................................................................... 117

Futera III/Fusion-Series HeatNet V3 Control Menu Tree ..................................................................... 119

Futera III/Fusion HeatNet V3 Control Advanced Menu Tree ............................................................... 120

Worksheet .............................................................................................................................................. 121

FEATURES & SPECIFICATIONS HeatNet Control V3

Page 5

Introduction

The Futera III/Fusion-Series V3
HeatNet Control

The Futera III/Fusion-Series V3 boiler control is the third
generation of the HeatNet control platform. Control
hardware has been added to make use of many new heating
applications. These new features are outlined in the Features
& Specifications section.

Two versions of the Control are available. The full version
and the “Lite” version. The Full version is available as an
option. Consult the factory or sales. The Lite version:

1.) Supports (1) system pump

2.) HeatNet Online monitoring requires a Touchscreen

display on the Master boiler (Full and Lite).

3.) Only a 0-10 VDC output (no 4-20mA)

4.) Does not support (3) alternate staging relays

5.) Pluggable colored terminal strips.

The Futera III/Fusion-Series boiler control is designed to
provide the Futera III/Fusion-Series of boilers with an
integrated boiler management system on every boiler.
Designed for the Air-Fuel coupled Futera III/Fusion-Series
boilers, the Futera III/Fusion-Series HeatNet control
provides for optimized heating efficiency without the need
for a “wall mount control”. Since the Futera III/Fusion­Series modular control method is based on digital
communications, analog control signals are not required.
Although the use of analog control signals is still supported
(4-20mA control loops and 0-10vdc control voltages), a
higher level of control precision, repeatability, and feedback
is gained with digital communications control.

With the Futera III/Fusion-Series, optimized heating
efficiency is accomplished by setting the Modulation
Maximum (Mod-Max) setting to exploit the inverse
efficiency curve. This value can be adjusted so that as each
boiler is added, it operates at its maximum turndown. This
allows the maximum number of boilers to operate at their
lowest inputs, until all boilers are firing. Once all boilers are
firing, full range modulation control is allowed. An outdoor
reset function is also provided to assist in the optimized
heating efficiency of the Futera III/Fusion-Series boilers.

The Futera III/Fusion-Series boiler with the Futera
III/Fusion-Series H-Net control, can be operated in multiple
ways:

1. As a standalone boiler.

2. A boiler, in a Boiler Network, using the HeatNet®

(H-Net®) protocol.

3. A Member boiler to a boiler management system with

multiple input control methods.

The primary purpose of the control is to maintain the boiler
water temperature at the supply or the header sensor using a
target setpoint. While performing this task, the control also
monitors dedicated external limits in a limit string and
provides an orderly shutdown and fault indication in the
event of a tripped limit. The monitored limits include a
HIGH LIMIT AQUASTAT, LOW WATER CUTOFF,
GAS PRESSURE, FLOW, IGNITION CONTROL fault,
GAS VALVE alarm, VARIABLE FREQUENCY DRIVE
alarm, and other optional or user selectable limits.

The HIGH LIMIT circuit is independent of

the control and shuts down the ignition
control and the boiler if the control board or
other component of the boiler was to
malfunction. The control will continue to
function and report the fault, but its ability to
control the boiler will end.

Each Futera III/Fusion-Series boiler employing this control
can function as either a Master or a Member. This allows
one boiler (Master) to be in control of a target temperature.
The other boilers (Members) only respond to the commands
issued by the Master. If using an external control, all boilers
can be setup as Member s. The following will define the
roles of Master and Member.

Master

A boiler becomes a Master when a temperature sensor is
connected to the J10 “SYSTEM HEADER” terminals. The
sensor is auto-detected.

The Master senses and controls the common system
header/loop water temperature using a system setpoint. It
uses any boilers it finds (over the H-Net communications
cable) to accomplish this. It can also monitor the Outside
Air (OA) temperature to provide outdoor reset functionality.

Only one Master is allowed in a system.

When operating as a Master, the boiler provides a control
method using a PID algorithm to regulate water
temperature. This algorithm allows a single boiler (Master),
or multiple (Master + Member) boilers. There are two PID
algorithms that can be used. One PID is used for space
heating, and the other for Domestic Hot Water (DHW)
heating. This allows both space and DHW to be controlled
simultaneously.

FEATURES & SPECIFICATIONS HeatNet Control V3

Page 6

Figure 1 Heat band

The control algorithm is based upon a Heat Band, at the
center of which is the setpoint. While below the Heat Band,
boilers are staged on and modulated up until the Heat Band
is entered. Once in the Heat Band, modulation is used to
maintain setpoint. Boilers are shut down only when the top
of the Heat Band is breached. Timers are also used to
prevent short cycling.

The control algorithm is based upon a Heat Band, at the
center of which is the setpoint. While below the Heat Band,
boilers are staged on and modulated up until the Heat Band
is entered. Once in the Heat Band, modulation is used to
maintain setpoint. Boilers are shut down only when the top
of the Heat Band is breached. Timers are also used to
prevent short cycling.

While staging the boilers on, a modulation clamp

ADVANCED SETUP: MODULAR BOILER SET:
MOD MAX-LAST FIRE is used to hold the boilers at a

lower fire rate until the last boiler is fired. Once the last
boiler fires, the modulation clamp is removed and all boilers
are allowed to fire above this clamped percentage up to

100%. This “boiler efficiency” clamp is defaulted to 70%

and thus limits all of the boilers individual outputs to 70%
until the last boiler fires. All running boilers modulate up
and down together, always at the same modulation rate. As
a general rule, this percentage should be no lower than twice
the minimum turndown to minimize short cycling.

When additional boilers are needed to achieve setpoint in
the system, the Master boiler employs an ADAPTIVE
MODULATION algorithm to prevent over firing of the
system. The Master communicates over the H-Net to view
the exact status of each Member boiler. When a new boiler
is added, the Master boiler adjusts the system modulation
rate lower to compensate for the BTUs that will be
introduced by the newly added boiler. This adjustment
occurs when the newly added Member boiler enters its ON
CALL state (default setting). This can be changed to PILOT
when the new boiler is called using the menu:

ADVANCED SETUP: ADAPTIVE MOD: DROP
DOWN. Once the Main Valve (on the newly added boiler)

is opened, and the DELAY RELEASE timer equals zero,
the PID algorithm is allowed to control the system
modulation. Setting the DELAY RELEASE timer will
allow some “soak” time of the newly added boiler before
releasing modulation control to the PID.

The ADAPTIVE MOD menus are disabled

on a Member boiler, but are still visible.

Member

If a “SYS/DHW HEADER” sensor is not connected to J10,
a boiler always defaults to the role of Member.

The Member boiler can operate as part of a multi-boiler
system or as a standalone unit.

In a multi-boiler system the Member typically receives its
command signals from a designated Master-boiler. It is also
capable of receiving inputs from an external control system.
The boiler responds to these signals, to start/stop the burner,
and/or to modulate the firing rate. The outlet water
temperature is also monitored. If the outlet temperature
approaches the operating limit temperature setpoint
(adjustable), the boilers firing rate is limited and its
modulation value is reduced to minimize short-cycling. If
the operating limit is exceeded, or if an interlock trips, the
boiler is shut down. When connected with a network cable,
in a Master/Member role, the Members' status is
interrogated by the Master boiler.

Any standalone boiler will perform

better when controlling to a header sensor.

A Fusion, as a standalone boiler,

requires a header sensor to control properly.

In a standalone installation the Member typically receives
its command signals internally and operates based upon the
outlet water temperature input and the established settings in
the menu (Local Set-point) to start/stop the burner, and/or to
modulate the firing rate. If the operating limit is exceeded,
or if an interlock trips, the boiler is shut down. As in a
multi-boiler system, a standalone Member boiler is also
capable of receiving inputs from an external control system.

When using the H-Net network cable in a Master/Member
system, the system setpoint is sent from the Master as a
digital signal, along with the modulation value to control
firing rate. It also receives its command to start or stop over
the H-Net cable. Also, the SYSTEM CLOCK only needs to
be set on the MASTER. The Master will then set the time
on all Member boilers.

If not using the H-Net protocol (cable), an external control
can send a 4-20mA or 0-10V signal along with a 4-20mA
enable signal to control the setpoint or firing rate. The boiler
may also be treated as a 2-stage boiler or an ON-OFF boiler
using the dedicated T-inputs.

FEATURES & SPECIFICATIONS HeatNet Control V3

Page 7

Features & Specifications

HeatNet Version 3.x Discontinued
Features

1. With this hardware release the service power, switched

power, and the power switch connector have been
removed. These were available on prior versions of the
HeatNet control. Upgrading to this control from prior
versions will require some wiring changes using an
upgrade kit.

2. The J10B input is no longer supported for proving the
damper. Damper proving switches will need to be wired
to J12B, 7 & 8.

3. If a stack sensor is used with this version, the alarm
silence switch cannot be connected and the
disconnected wires should be terminated appropriately.

Silencing the alarm can be done by holding the BACK
and SELECT keys down at the same time.

Hardware Version 3.x Control
Additional Features
(Identified by circuit board color: BLACK)

1. Support for (2) Circulator pumps (1 if Lite version).
Two rotation modes are provided: Based on system
runtime or system pump runtime hours. Pump failure
switchover/retry mode.

2. Warm weather shutdown, (2) pump jog (1 if Lite
version) and local pump jog to keep pumps from
seizing.

3. The Modbus, BACnet or LonWorks communications
port can be accessed concurrently with the USB port
(HeatNet Control Pro). The BACnet, LonWorks, or
Modbus connections do not need to be disabled to use
the USB ports.

4. The DHW pump and the Local Pump relay connections
now provide a normally closed contact. This allows for
the use of a power open/power close valve.

5. Support for 5mA 0-10v control signals using third party
controls.

6. Support for (2) display types: Vacuum Florescent and
Color LCD using the same 20 pin ribbon cable. The
color LCD provides an interface for the HeatNet Online
monitoring.

7. System Return sensor input.

8. Enhanced boot loader and firmware storage. One

firmware storage location for user updates. One
firmware program that always remains resident so that a
factory program can be restored. Primary loading is
with a flashdrive. The P3 shunt restores the previous
firmware.

9. 32 bit Microcontroller operating @ 64 Mhz with 5-

stage pipeline, and prefetch cache.

10. (3) Stage control relay outputs for TBD applications.

11. Backwards compatible with existing HeatNet versions

1.x and 2.x controls and applications.

12. Support for 135 Ohm control actuators.

13. 1k Platinum Stack sensor.

14. Flow meter input or BMS GPM input/control

15. Dual PID controls. One for space heating and one for

DHW heating. Allows for simultaneous DHW/Space
heating.

Standard Features Overview

1. Five levels of external control inputs, including

modulation and staging that provide application
flexibility.

2. Digital Communications Control (analog 4-20mA and

0-10vdc control supported, but not required).
a. Boiler to Boiler : HeatNet (H-Net)
b. Building Management System (MODBUS,

Optional BACnet or LonWorks) to Boiler

3. Distributed control using the HeatNet (H-Net) protocol

for up to 16 boilers. Eliminates the need for “wall
mounted” controls.

4. Analog Control 4-20mA and 0-10vdc (5mA minimum

current) signals supported.

5. System/Boiler operating status text display

6. Interlock, Event, and System logging with a time

stamp.

7. Advanced PID algorithm optimized for the Futera

III/Fusion-Series boilers.

8. (4) Dedicated temperature sensor inputs for: Outside

Air Temperature, Supply (Boiler Outlet) Temperature,
Return (Boiler Inlet) Temperature, and Header
(Common System Supply) Temperature.

FEATURES & SPECIFICATIONS HeatNet Control V3

Page 8

9. Automatically detects the optional temperature sensors

on power up (Outdoor Air Temp sensor is enabled in
the settings menu).

10. Menu driven calibration and setup menus with a bright

(Adj.) 4 line Vacuum Fluorescent Display.

11. (8) Dedicated 24vac interlock monitors, and 8 dedicated

120vac system monitors used for diagnostics and
providing feedback of faults and system status.

12. Multiple circulator pump control modes.

13. Combustion Air Damper control with proof time,

support for a common combustion air damper.

14. USB/RS485 network plug-in to allow firmware updates

or custom configurations.

15. Optional BACnet or LonWorks interface.

16. Alarm Relay dry contacts, and Audible Alarm.

17. Runtime hours, and Cycles (based on Main Valve

Open).

18. Outdoor Air Reset with programmable setpoint and

ratio.

19. Time of Day clock to provide up to (4) night setback

temperatures.

20. Failsafe mode when a Building Management System is

controlling setpoint. If communications is lost, the
boiler/system automatically transfers to local boiler
setpoint control.

21. Rotation Methods (Lead-Lag): True Rotation (based on

boiler runtime) is default. First-On First-Off (FOFO),
Last-On First-Off (LOFO) and MIXED are optional.

22. Programmable password protection to secure the

programmable settings.

23. Remote 4-20mA setpoint control using a mapped

setpoint range to the 4-20mA control signal.

24. Freeze Protection allowing automatic starting of

boiler(s) using (2) Failsafe modes.

25. Adaptive Modulation. When additional boilers are

called, the Master adjusts all boilers fire rates to
compensate.

26. Mixed boiler types in a system.

27. Support for Domestic Hot Water (DHW) using a 10k

Sensor or a dry contact input from a tank thermostat.

28. Domestic Hot Water relay for use with a pump or

valve.

29. On-board power and socket for Protocessor

BACnet/LonWorks module.

30. HI/LO relay control option from connector J4

31. Resettable Fused interlock power circuit.

32. Additional terminal connector for H-Net shielded cable.

33. Backwards compatible to Version 1.x hardware.

34. Communications board integrated with the main board

from version 1.x control.

35. Base Loading of (1) boiler.

36. Domestic Hot Water time out for maximum DHW

runtime.

FEATURES & SPECIFICATIONS HeatNet Control V3

Page 9

Specifications

Control Microprocessor based PID modulating control (NOT a safety limit)

Environment -40 °F to 140 °F, <90% RH non-condensing

Input Power 24 VAC, 500 mA

Relays 1 System Pump (Lite version), 2 System Pumps (Full Version), Damper, Circulator, Alarm, DHW

Pump (v2.x), 8A 250 VAC resistive* - Refer to wiring diagram for application specific ratings

K8 on J4.2 &.6 for Base Loading

AC Interlocks 24 VAC – 120 VAC input

Control Inputs AA, Heat Demand, 4-20mA Enable, OA override, T1-T2 (dry contact inputs)

4-20mA, 0-10 VDC

Dimensions 9” wide: 6” high: 2” deep

Temperature Sensors NTC thermistor, 10K @ 77 °F, 335.67K @ -40 °F, 185 @ 150 °F ,+/- 1 F

USB 1.0

RS485 MODBUS Modbus RTU

Boiler-to-Boiler HeatNet (H-Net)

Network Optional LonWorks, BACnet available bridge to MODBUS port

FEATURES & SPECIFICATIONS HeatNet Control V3

Page 10

Components & Accessories

Part Number

Component Description

16-0046

Futera III/Fusion-Series Control Board Version 3.x Full- Optional

16-0047

Futera III/Fusion-Series Control Board Version 3.x Lite - Standard

40-0088

Graphics Display Board

40-0091

Graphics Display, Color Touchscreen (HeatNet Online Interface)

16-0026

Temperature probe (bullet type, 1x.250 inch) ACI/10K-CP-BP

14-0325

Supply, Header, Return Sensors ACI 10k-CP-I-NW

14-0328

ACI-X/(2) CP-PO-4 4” probe with dual sensor

14-0329

ACI-X/(2) CP-PO-6 6” probe with dual sensor

13-0104

3” Immersion Well

14-0319

Outside Air Sensor with Housing ACI 10k-CP-O

Installation & Operation Manual

44-0060

RJ45 Communications Cable Assembly, 25 feet

40-0115

Ribbon Cable Assembly (Display Control)

44-0061

USB Cable Assembly, 6ft

14-0354

MODBUS to BACnet Bridge

14-0353

MODBUS to LonWorks Bridge

14-0356

MODBUS to HeatNet Online Module

SETUP & OPERATION HeatNet Control V3

Page 11

SETUP & OPERATION

Basic Multi Boiler System Operation

For boiler system setup/installations please

refer to Refer to the 2008 ASHRAE
Handbook, CH12 or later revision.

A basic multi boiler system typically uses boilers of the
same size and type. With HeatNet, this includes (1) Master
and (1-15) Member boilers. The boilers are connected
together using an H-Net communications cable effectively
creating (1) boiler. This allows the system heating BTUs to
be evenly distributed among all of the boilers. (See:, Typical
Single Boiler System, page 74).

Figure 2 Basic multiple boiler system

A basic multi boiler system can be configured using the
boiler menus to create custom systems/features. These
features are best described in the section: Default Settings

& Menu Item Description. Along with these menu
items are hardware support for many auxiliary
functions.

Once the system has been properly setup (all default menu
values used and H-Net addresses assigned), the system is
enabled by placing the REMOTE/LOCAL switch to the
LOCAL position on the Master boiler. All Member boilers
must have their respective switches in the REMOTE
position. When the Master boiler’s Heat Demand input
(LOCAL switch) closes, the system becomes operational
and will fire as many boilers as it needs to maintain the
header water temperature’s setpoint. See the DHW section
to fire to two setpoints.

When a boiler is to be fired in a multi boiler system (header
water temperature is below the heating band), the Master
checks the HeatNet boilers it has available. Then the Master
checks if a Lead Boiler is to be used (LEAD BOILER > 0).
The Master boiler then looks at which type of firing rotation
it has selected: LOFO, FOFO, TRUE (runtime), or MIXED.
In our example we will use the TRUE (runtime) rotation
since it is the default.

The Master now checks all of the runtimes to determine
which boiler has the least runtime based on the MIN
RUNTIME setting in ADVANCED SETUP: FIRING
MODE:. The MIN RUNTIME setting is the minimum
runtime interval in hours that is used to compare boiler to
boiler runtimes.

Once the boiler to fire has been determined, the Master
sends the command over the H-Net cable to fire that boiler,
and resets the ADD BOILER delay timer to prepare for the
next boiler to fire. If the header water temperature is still
below the heating band, and the ADD BOILER delay timer
has expired to zero, the process is repeated until the header
water temperature enters the heating band.

When a boiler receives a command to fire:

1. The system pump relay is enabled and the H-Net

control displays 'Flow Wait' until the flow-switch closes
between J11A, 1 & 2 within the programmed time
(10seconds).

2. All elements in the interlock string, terminated between

J11A and J11B, must be closed before the sequence is
allowed to continue.

3. If all interlocks are closed relay K5 is enabled to

command the combustion-air damper open (if used).
The H-Net control displays 'Damp: Wait' until the
damper end switch closes on input DAMPER, J12B.

4. Relay K6 is enabled energizing the local pump (if

used). The H-Net control commences its 'Flow-Wait'
timer (adjustable 10–240 sec.). The flow switch contact
is checked on terminals J11B, 5 & 6.

5. With all the interlocks closed, the boiler start relay K1

is enabled and energizes terminal 6 on the ignition
control. This signal is present on J5 Boiler Start
Operator.

6. The ignition control begins its cycle and provides an

output signal from terminal 4 to the H-Net control J5
Blower. The H-Net control responds and provides an
output signal to the VFD which sets the blower to the
programmed pre-purge speed.

7. After air-flow is established the ignition control waits

for the air switch to close. When the air switch closes it
provides an input to terminal 7 and pre-purge timing
commences. The H-Net display indicates 'Pre Purge'.

8. When purge is complete the ignition control energizes

the pilot gas valve from terminal 8, and the spark
generator from terminal 10, beginning a 10-second Pilot
Flame Establishing Period (PFEP). The H-Net control
responds to J5 Pilot Valve and provides an output
signal to the VFD which sets the blower to the
programmed ignition speed. The H-Net display
indicates 'Pilot'.

9. At the end of the PFEP the spark generator is de-

energized. If the pilot flame is detected, by the UV
scanner, the ignition control energizes the main gas
valve from terminal 9 to J5 Main Valve. The H-Net
display indicates 'Run'.

SETUP & OPERATION HeatNet Control V3

Page 12

10. If main-flame is detected the H-Net control holds the

burner at the low-fire rate for the MODULATION
DELAY time period. After this timer expires, the PID
allows the boiler to modulate and places the boiler into
the running state.

As boilers are added to the system settings in the ADVANCED
SETUP: ADAPTIVE MOD: DROP DOWN menu determines
when the modulation rate drops down to compensate for the
newly added BTUs. For the drop down to be active, one
boiler needs to be running when a new boiler is added (see:

Introduction: The Futera III/Fusion-Series H-Net Control:
Master).

If all boilers are firing, the modulation rate is released to go
to 100%. If all boilers are not firing, the modulation is
limited to the MOD-MAX clamp value. The MOD-MAX
clamp is used to keep the boilers running as efficiently as
possible. The following Mixed Boiler System Operation:
Selecting Mixed Boilers section outlines this with examples.

NOTE: If the boiler is running as a standalone boiler or

is direct modulated (including the AA input),
the MOD-MAX clamp will also be in effect
for the ADD BOILER DELAY time. This is to
minimize thermal shock to the boiler.

Once the header water temperature is in the heating band,
only the modulation rate is used to achieve the target
setpoint. The system will maintain the setpoint until the load
demand increases or decreases.

As the load decreases, the header water temperature will
start approaching the top of the band. The PID now lowers
the modulation rate to the boilers, attempting to keep the
temperature within the heating band. If the system is
delivering too many BTUs, the water temperature will cross
the top of the heating band.

When the header water temperature first exceeds the top of
the heating band, the boilers are again checked for the one
with the most runtime. The selected boiler will turn off
immediately and a shed boiler delay timer will be loaded
with the delay time. This time will need to expire before the
next boiler will be stopped, but only if the header water
temperature remains above the heating band. This timer is
used to allow the header water temperature to return back
into the band when a boiler is stopped. When a boiler is
stopped there is a fixed rate of BTUs (Min Fire) that will be
removed (PID discontinuity to modulate from Min Fire to 0
BTUs on a boiler). The timer allows for this loss of BTUs.

This cycle will continue until the call for heat is satisfied or
the Warm Weather Shutdown feature is enabled.

Mixed Boiler Types Using
Priority Sets

Using the Basic Multi Boiler System Operation, a MIXED
boiler Priority method may be added to control condensing,
non-condensing, base load, or other boiler SETs in a system
together. These sets compose a system which provides for
optimal performance and economy. Having dedicated sets
of boilers gives the system engineer a tool to create many
different boiler systems.

A boiler set can be constructed by simply setting the firing
Priority on each boiler (to be in a set) at the same priority.
Setting all (example) condensing boilers to the highest
Priority of 1, and then setting all (example) non-condensing
boilers to a Priority of 2, will create (2) sets of boilers, one
condensing and the other non-condensing. Once this is
done, the Priority 1 set of condensing boilers will have a
firing order that has a higher Priority and is independent of
the other non-condensing set with the lower priority. The
boiler set with the highest Priority can then be fired based
on a conditional settings menu. The lower Priority set will
follow. If the priority set is used with condensing and non­condensing boilers a boiler may also go offline when a
return temperature is too low.

Boilers will be staged on and off using the ADD and SHED
timers as always, but the boilers can now be grouped.

Mixed Boiler System Operation

Starting Boilers:

When a boiler is to be fired (water temp is below the heating
band), the Master checks the HeatNet boilers it has
available. The Master boiler then looks at which boilers are
returning Priority firing status (set on a boiler in:

(ADVANCED SETUP: SYSTEM: BOILER TYPE:
PRIORITY: 1). If the Start condition for the Priority 1set is

met (ADVANCED SETUP: FIRING MODE: MODE:
MIXED: SET FIRST (example), the Master or Member
boiler that is configured as PRIORITY 1, with the lowest
runtime, will be fired FIRST (example).

As long as the start condition for Priority 1 is met, all
boilers in the PRIORITY 1 set will fire based on runtime.
Once all boilers in the PRIORITY 1 set have fired, the
PRIORITY 2 set of boilers will fire based on runtime.

If the Start condition changes and/or is not met (such as
with: OA T or RET temp), the PRIORITY 2 set of boilers
will fire first/next based on runtime. This has the effect of
flipping the Priority of the sets.

Stopping Boilers:

When a boiler is to be stopped (water temp is above the
heating band), the Master checks the HeatNet boilers it has

SETUP & OPERATION HeatNet Control V3

Page 13

available. The Master boiler then looks at which boilers are
returning Priority firing status (set on a boiler in:

(ADVANCED SETUP:FIRING MODE: MODE:
MIXED: SET LAST (example) If the Stop condition for

Priority 1 is met, the Master or Member boiler that is
configured as PRIORITY 1 with the highest runtime will be
stopped LAST (example). As long as the stop condition and
SHED DELAY time are met, all remaining PRIORITY 1 set
of boilers will stop based on runtime. If the Stop condition
changes and/or is not met (such as with: OAT or RET

Temp), the PRIORITY 2 set of boilers will stop first/next
based on their highest runtime.

A boiler’s firing Priority can be designated as such in:

ADVANCED SETUP: SYSTEM: BOILER TYPE:
FIRING PRIORITY: 1 menu on each boiler. A Priority of

‘1’ is the highest priority, a ‘2 the lowest (default is always

2).

Figure 3 Mixed Boilers: Example: Condensing/Non-Condensing

In the example Mixed Boilers: Condensing/Non­Condensing, condensing boilers and non-condensing boilers

are used, but other combinations may also be used. Another
example could use (2) small boilers and set them to
Priority 1 and then use (3) larger boilers and set them to
Priority 2. Using these Priority settings (with the conditions
menu), the small boilers can run first during the shoulder
months (Spring and Fall) and the larger boilers can fire last
during the colder Winter season (base loading set).

Before the MIXED method can be used, the firing mode on
the Master boiler must be set to MIXED. ADVANCED
SETUP: FIRING MODE: MODE: MIXED. Pressing the
SELECT key when the cursor is pointing to MIXED will
enter the conditions menu. The START and STOP
conditions for starting and stopping the Priority boiler set
may be configured here. Temperatures are adjustable.

Once the conditions menu has been entered, the firing order
and stop order of the Priority 1 boiler set can be selected
based on up to (3) conditions in the conditional settings
menu. All conditional settings apply to the Priority 1 boiler
set. When the conditional settings do not apply to the
Priority 1 set, the conditional settings will apply to the
Priority 2 boiler set.

START P R I O R I T Y 1
>SET : FIRST
STOP P R I O R I T Y 1
SET : OAT < 15°F

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Start/Stop Priority Conditions

The following is an example using mixed
condensing and non-condensing boilers:

FIRE FIRST

Condensing boilers may be configured to fire first (set to
PRIORITY 1) when:

2. The Return water temperature is below 140F and

condensing occurs. (The Master’s return water sensor
would need to be moved to the header return.)

3. The Outside Air Temperature is above a setpoint

determined by the system configuration. This setpoint
ensures that the more efficient condensing boilers run
first during shoulder months (Spring and Fall) when
minimal heating is required. Below this setpoint, larger
boilers should be brought on first to “base load” the
system.

4. Greater efficiency is required.

STOP FIRST

Condensing boilers may be configured to stop first (set to
PRIORITY 1) when:

The Return water temperature is above 140F and
condensing is minimized, thus leaving the larger lower cost
boilers running to carry the load.

1. The Outside Air Temperature is below an adjustable

setpoint determined by the system configuration. This
setpoint ensures that the larger non-condensing boilers
run during the coldest months when maximum heating
is required. Above this setpoint smaller condensing
boilers should be brought on first to run the system as
efficiently as possible.

2. Maximum heating is required

START PRIORITY 1 SET

Selections (always the lowest runtime first):

The condensing boiler set (Priority 1) has a

higher Priority to fire when one of these
conditions is met. Values are adjustable.

FIRST: The condensing boilers (Priority 1) are always
started FIRST

OA T > 15F: The condensing boilers (Priority 1) are
started when the OA temperature is greater than the Mixed
Boiler Outdoor Air Temperature setting.

RET < 140F: The condensing boilers (Priority 1) are
started when the Return water temperature is less than the
Mixed Boiler Return temperature setting (This may not
applicable in most configurations since the local return

temperature on the Master is used to provide a difference
temperature across the heat exchanger. A System Return
sensor will be required. However, the return temperature
sensor may have been moved on the Master to provide
system return temperature on existing installations and is
still supported).

STOP PRIORITY 1 SET

Selections (always the highest runtime first):

The condensing boiler set (Priority 1) has a

higher Priority to stop when one of these
conditions are met. Values are adjustable.

LAST: The condensing boilers (Priority 1) are always
stopped LAST.

OA T < 15F: The condensing boilers (Priority 1) are
stopped first when the OA temperature is less than Mixed
Boiler Outdoor Air Temperature.

RET > 140F: The condensing boilers (Priority 1) are
stopped first when the Return water temperature is greater
than the Mixed Boiler Return temperature. (This may not
applicable in most configurations since the local return
temperature on the Master is used to provide a difference
temperature across the heat exchanger A System Return
sensor will be required. However, the return temperature
sensor may have been moved on the Master to provide
system return temperature on existing installations and is
still supported).

Start/stop settings

Any combination of Start Conditions and Stop Conditions
can be used to optimize the mixing of condensing
(Priority 1) and non-condensing boilers (Priority 2) for best
performance/economy.

The default settings for the start and stop conditions of the
condensing set are:

The default start setting always starts the condensing boilers
(Priority 1 example) first, except for the lead boiler setting.
The lead boiler will always start first if enabled, unless
there is a boiler already running (this includes a Member
boiler in LOCAL). The default stop condition setting always
stops the condensing boilers (Priority 1) last.

If prolonging the life of the heat exchanger(s) on non­condensing boilers is very important, consider starting the

START P R I O R I T Y 1
>SET : FIRST
STOP P R I O R I T Y 1
SET : L A S T

SETUP & OPERATON HeatNet Control V3

Page 15

condensing boilers (Fusion-Series) when the return water
temperature is below 140F.

The return water temperature sensor would

need to be moved from the Master’s return
inlet to the system return. The EXCHGR

DELTA may need to be adjusted in SETUP:
AUX FUNCTIONS: HEAT EXCHANGER

to prevent the Master from going to ½ input
when a high DELTA T is reached.

This method would lead to the non-condensing boilers
carrying the load when the system temperature stabilizes
above 140F, since non-condensing boilers will start first
with the Return water temperature is > 140F. The
condensing boilers can then be stopped first when the RET
water temperature is above the 140F. Remember, any
combination of the Start and Stop conditions may be applied
for best performance and economy in the system. Also, non­condensing boilers may be set to go offline when a return
temperature is too low using the SETUP: AUX
FUNCTIONS: HET EXCHANGER: TEMP DISAB menu.

Base load boilers can also be mixed in the same way as
condensing and non-condensing boilers. The base load
boiler(s) can be prioritized in one set (example, Priority 2)
and non-base load boilers (Priority 1). The non-base load
boilers can then be set to fire first and once they are all
firing, the base load boiler would fire.

To minimize the cycling of a large base load boiler, consider
using the stop condition. Change it to the OAT < 15F
(Outside Air Temperature) condition. This setting may be
used to stop the Priority 1 boiler set when the OAT drops
below the OAT setpoint, thus leaving the large base loaded
boiler on and shutting off the condensing boilers first. This
is also true when using the OAT setting to start the
Priority 1 boiler set when the OAT is above the start
setpoint. To use temperatures as start and stop conditions,
the system design temperatures must be known.

Selecting Mixed Boilers

There are a few factors to consider when choosing which
type of boilers to use in a mixed system. These factors need
to be considered when boilers are added or shed. When
BTUs are introduced into the system by adding boilers, the
amount of introduced BTUs should be smooth (linear). If
these factors are not considered, discontinuity in BTUs may
occur when boilers are added and as a result, short cycling
will occur.

1. Turndown: This is the ratio of minimum fire rate to
maximum fire rate: Example: a 20% minimum
modulation = 5:1 turndown (100%mod / 20% mod). A
(1) million BTU boiler = 200,000 BTUs minimum
input.

2. MOD MAX CLAMP: This value determines the

maximum modulation % at which the boilers will fire
to, until all available boilers are firing.

3. Total System BTUs.

4. Desired Effective Turndown. This is the lowest

firing rate of the system relative to the maximum firing
rate of the system. The larger the value, the lower the
BTUs that can be delivered to a light load.

5. Piping.

Mixed System Type 1:
High System Turndown

The following examples are of mixed boiler systems with
high effective system turndown and fault tolerance built in.
When boiler types are the same, the system turndown is

limited to the boiler’s min input and fault tolerance is

always present. When the system has mixed boiler types,
consideration needs to be taken on what types can be mixed
properly to achieve a high system turndown and provide
some fault tolerance.

Fault tolerance allows for one boiler in the Priority 1 system
to fail and any boiler(s) in the Priority 2 system to fail and
still provide near linear (continuity) BTU response when
adding boilers. This is illustrated in the following examples
using the Boiler System Response graphs.

The Futera III/Fusion-Series Mixed Boiler System
(examples) is advantageous in providing low BTU input for
light loads and high BTUs for heavy loads. The effective
system turndown minimizes short cycling when light loads
are present by assigning smaller boilers to Priority 1,
running them first, and then stopping them last.

In order to achieve the high effective

turndown, smaller boilers are required
(plumbing considerations need to be
considered here due to differing flow/volume
characteristics through the large and small
boilers).

Example Systems:

Figure 4 Non-Mixed Boiler System

System

MMBTU

Effective

Turndown

MOD
MAX

MB/MW 4:1

10.0

20:1

70%

2000, 2000, 2000,

2000, 2000

5.0

20:1

70%

1000, 1000, 1000,

1000, 1000

2.5

20:1

70%

500, 500, 500, 500,

500

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Page 16

With the traditional Non-Mixed boiler system, the effective
turndown increases by the turndown ratio for every boiler
added. The min fire rate is equal to the minimum BTUs that
can be delivered to the system.

Number of boilers * Turndown Ratio = Effective System
Turndown: 5 * 4:1 = 20:1.

Figure 5 Mixed Boiler System

System
MMBTU

Effective

Turndown

MOD
MAX

Priority 1

MB/MW

4:1

Priority 2

MB/MW

4:1

4.5

24:1

46%

750, 750

1000, 1000,

1000

4.75

32:1

60%

500, 500

1250, 1250,

1250

6.5

26:1

45%

1000, 1000

1500, 1500,

1500

6.0

48:1

55%

500, 500,

500

1500, 1500,

1500

With the mixed boiler system, a lower minimum fire
rate/BTU can be delivered to the system by using small
boilers with larger boilers. This works in much the same
way as base loading.

Figure 6 Futera III/Fusion Boiler Btu Chart (MBH)

MB/MW

CB/CW

500

750

1000

1250

1500

1750

2000

Max Input

500

750

1000

1250

1500

1750

2000

Min Input

4:1

125

188

250

312

375

437

500

Mod Max

80%

400

600

800

1000

1200

1400

1600

Mod Max

70%

350

525

700

875

1.05

1220

1400

Mod Max

60%

300

450

600

750

900

1050

1200

Mod Max

50%

250

375

500

625

750

875

1000

When selecting the Priority 1 boiler(s) for a high effective
system turndown, the BTU Min Input is selected first. (See:
Futera III/Fusion Boiler Btu Chart). Next, the MOD-MAX
value of this Priority 1 boiler needs to be greater than: Mod

MAX % =

(Priority 1 ‘s Min Input + Priority 2 ‘s Min Input)

Max Input of the Priority 1 boiler

The reason for this is to keep the continuity of BTUs linear
without a BTU bump (discontinuity) when boilers are added
or shed. This is illustrated in the Boiler System Response 2
graph.

If redundancy is not required, the min inputs of the
Priority 1 boilers may be summed to lower the Mod Max %
value so smaller Priority 1 boilers can be used. The sum of
the min inputs would then need to be divided by the sum of
the Max Input of the Priority 1 boilers. The effect of this
would create a higher turndown. See: EXCEPTION NOTES:

Mod MAX % =

(((Priority 1 Min) * (#Priority 1’s)) + Priority 2 Min)

Max Input of Priority 1 boiler * (#Priority 1’s)

Example: (2) CB/CW500, (2) MB/MW1250
Redundancy: (125 + 312) / 500 = 88%
No Redundancy: (125 * 2) + 312) / (500 * 2) = 56%

EXCEPTION NOTES:

1. Mixing more than two different size/type boilers

becomes more complex than the scope of this manual
and is not recommended.

2. If using more than one Priority 1 boiler and the

calculated value is <

Priority 1Min * 2

Priority 1 Max Input

Use this result PLUS note 3 value as the
ModMax%.

3. Always add a few % (3-5%) to the calculated MOD

MAX % value to allow a guard band (tolerance).

4. If boilers are of different sizes, try to use larger Priority

2 boilers.

If the calculated Mod MAX % value is greater
than 99%, the combination cannot be used
since short cycling will occur.

Once the Priority 1 and Priority 2 boilers are selected, they
can be multiplied in each Priority set to achieve the desired
system design BTUs. If the # of boilers becomes a large
number, a Priority 1 boiler with a higher Min Input may
need to be selected.

While considering the MOD-MAX value, the lower the
MOD-MAX the greater the combustion efficiency since it
effectively limits the input rate. The Typical Efficiency of

SETUP & OPERATON HeatNet Control V3

Page 17

Non-Condensing Boilers chart can help illustrate how the
MOD-MAX value can affect the efficiency by limiting the
input until all boilers have fired. Non-condensing boiler
efficiency is relatively flat compared with condensing as
illustrated in the Typical Efficiency of Condensing Boiler
graph.

Figure 7 Typical Efficiency of Non-Condensing Boilers

Figure 8 Typical efficiency of condensing boilers

(GAMA BTS2000 method)

In the Mixed Boiler System table line 2 example, (2)
MB/MW 500s are set as Priority 1 and MB/MW 1250s set
as Priority 2. With a MOD MAX of 60%, each 500 can run
to 300M (600M total) before a 1250 is called ON (Add
Delay timer). Once both 500s are running and the 1250 is
called on, all (3) boilers will drop to a total of the 600M
BTUs: The sum of the 500, 500, and 1250 would equal
about 27% modulation: (.27 * 500M) + (.27 * 500M) + (.27
* 1.25MM) or: 135M +135M + 337M = 607M and operate
at higher combustion efficiencies (noncondensing boilers
have minimal effect individually, but can have an effect if
many are used).

If CB/CW Fusion boilers are substituted for the MB/MW
Futera III boilers, the efficiency is greatly increased due to
the condensing mode of these boilers. When using CB/CW
Fusion boilers, during the first 2850 MBTH of load, the
combustion efficiency is maximized by running the CB/CW

Fusion boilers from low to middle input rates. See: Typical
Efficiency of Condensing Boiler graph.

Figure 9 Boiler System Response 1

(2) MB/MW 500s, (3) MB/MW 1250s

When running non condensing boilers at low

input rates, the risk of condensing should be
considered.

The Boiler System Response 1 chart illustrates how each
boiler (in the example) is brought on and fires to 60%, drops
to a lower fire rate and then adds the next boiler (vertical
dashed lines). Once all boilers are firing, the modulation is
released allowing all boilers to fire to 100%.

Now, if (1) MB/MW 500 (one of the MB/MW 500s was
brought offline) were used with (3) MB/MW 1250s and the
Mod-Max is set to 60%, the MB/MW 500 would fire to 300
MBTUs and wait for the MB/MW 1250 (Boiler System
Response 2 graph). Now, the minimum input rate would be
312M (MB/MW 1250) + the 125M (MB/MW 500) (already
running, but dropped to low fire when the MB/MW 1250
fired), the total being 437M. With a 60% MOD-MAX
clamp, there would be 137 MBTUS more than needed and
added to the system when the MB/MW 1250 fired.

The PID algorithm would then compensate for the
discontinuity (bump) in BTUs and the MB/MW 1250 could
shut off (short cycle).

This discontinuity is observed in the graph below, (Boiler
System Response 2) where the jump from the MB/MW 500
@60% to the firing of the MB/MW 1250 is apparent.

0.00

0.10

0.20

0.30

0.40

0.50

0.60

0.70

0.80

0.90

1.00

0 1,000,000 2,000,000 3,000,000 4,000,000 5,000,000

Input, %

System Load, Btu/Hr

Blr 1+2+3 (2250 MBTU)

Blr 1+2+3+4 (3500 MBTU)

Blr 1+2+3+4+5 (4750 MBTU)

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Page 18

Figure 10 Boiler System Response 2

(1) MB/MW 500, (3) MB/MW 1250, 60% Mod­Max

To correct this would require the MB/MW 500 to set the
MOD-MAX to roughly 90% (Boiler System Response 3: not
as efficient as it could be when using CB/CW Fusion
boilers) in order to have a linear BTU transfer when the
MB/MW 1250 is added (fired).

Figure 11 Boiler System Response 3

(1) MB/MW 500, (3) MB/MW 1250, 90% Mod­Max

An MB/MW 500 running with a MB/MW 1250 may not be
an optimal choice unless (2) MB/MW 500s are used in the
Priority 1 set or (3) MB/MW 500s and one is allowed to be
taken offline.

A system employing this redundancy where (1) is allowed
to be taken offline is listed in the MIXED BOILER SYSTEM
chart. This system uses (3) MB/MW 500s and (3) MB/MW
1500s. Two of the MB/MW 500s are treated as one when
adding the min inputs of the Priority 1 set.

Figure 12 Boiler System Response 4

(2) MB/MW 500s, (3) MB/MW 2000s

The Boiler System Response 4 graph illustrates another
system where 80% is used as the MOD-MAX clamp. With
this example, when using all non-condensing boilers, the
system can maximize the use of the smaller boilers before
calling the larger ones.

In summary, the system should be tuned using the boiler
selection charts and the MOD-MAX value. Since selecting
the Priority 1 boiler is integral to the fault tolerance of the
system, it is important to note any discontinuities in BTUs if
a Priority 1 boiler fails when multiple Priority 1 boilers are
used.

Mixed System Type 2:
Condensing / Non-Condensing

This mixed system may also have mixed boilers with
differing sizes as outlined in the Mixed System Type 1:
High System Turndown section. In the following examples
condensing high mass boilers will be used with non­condensing low mass boilers. The reason for creating a
mixed system is primarily to control the system cost.

0.00

0.10

0.20

0.30

0.40

0.50

0.60

0.70

0.80

0.90

1.00

0 1,000,000 2,000,000 3,000,000 4,000,000 5,000,000

Input, %

System Load, Btu/Hr

Blr 1+2 (1750 MBTU)

Blr 1+2+3 (4250 MBTU)

Blr 1+2+3 (3000 MBTU)

0.00

0.10

0.20

0.30

0.40

0.50

0.60

0.70

0.80

0.90

1.00

0 1,000,000 2,000,000 3,000,000 4,000,000 5,000,000

Input, %

System Load, Btu/Hr

Blr 1+2 (1750 MBTU)

Blr 1+2+3 (4250 MBTU)

Blr 1+2+3 (3000 MBTU)

0.00

0.10

0.20

0.30

0.40

0.50

0.60

0.70

0.80

0.90

1.00

0 1,000,000 2,000,000 3,000,000 4,000,000 5,000,000

Input, %

System Load, Btu/Hr

Blr 1+2+3 (3000 MBTU)

Blr 1+2+3+4 (5000 MBTU)

Blr 1+2+3+4+5 (7000 MBTU)

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Page 19

Figure 13 Mixed Condensing/Non-Condensing Boiler

System

Local Pump

Local Pump

MASTER

Condensing

MEMBER 1

Condensing

HNETHNET

Header Sensor

System Return Sensor

HNET

Local Pump

Local Pump

System Pump

MEMBER 2

Non-

Condensing

MEMBER 3

Non-

Condensing

Priority 1 Set Priority 2 Set

M

Combustion Air Damper

Outdoor Air Sensor

Outdoor Air

Sensor

Figure 14 Mixed Boiler System

System
MMBTU

Effective

Turndown

MOD

MAX

Priority 1

CB/CW 4:1

Priority 2

MB/MW

4:1

4.5

24:1

60%

750, 750

1000, 1000,

1000

4.75

32:1

60%

500, 500

1250, 1250,

1250

6.5

26:1

65%

1000, 1000

1500, 1500,

1500

6.0

48:1

65%

500, 500,

500

1500, 1500,

1500

For the examples, the RBI FIII/Fusion series water heaters
will be used. These boilers are non-Condensing, fully
modulating, low mass, and HeatNet compatible.

The Mixed Boiler System table show some examples of
mixed systems using different sizes along with Fusion
condensing (Priority 1) and Futera III non condensing
(Priority 2) boilers.

Using the boiler charts and the examples used in: Mixed
System Type 1: High System Turndown, a mixed boiler
system can be designed. The Priority 1 boilers should be
setup so as to keep the non-condensing boilers from seeing
return water temperatures of less than 140F to ensure a long
heat exchanger life.

Normally, the Priority 1 boilers will fire first. Once all the
Priority 1 boilers are firing, the next boiler to fire (after the
ADD BOILER timer expires) would be the Priority 2 (non­condensing). If the return water temperature has not come
up to ~140F, the non-condensing boilers could fire in a
condensing mode. The ADD BOILER delay timer would
have to be set to a long enough period to ensure this does

not happen. Even then, the load may be too great. The
following note will explain an alternative way (not
depending on the ADD BOILER DELAY) to keep non­condensing boilers from firing in a condensing mode.

When running with a remote BMS setpoint, care must be
taken that an Outside Air reset setpoint (or other setpoint)
sent by the BMS is not set too low. If the BMS system is
controlling the setpoint close to the condensing temperature,
the return water temperature may never rise sufficiently to
keep boilers out of a condensing mode. HeatNet online is a
good way to monitor this scenario if suspected.

If the firmware version for a HeatNet V2

board is at least 3.47(or a version 3
board), the non-condensing boiler may hold itself off from
being added to the HeatNet Master’s available to fire list.
This would effectively keep the non-condensing boiler
from firing in a condensing mode, but as a result, may not
satisfy the system setpoint.

In order to use this feature, the version 2 board would
need to monitor the system or local return temperature.
This can be done locally by setting SETUP: AUX
FUNCTIONS: HEAT EXCHNAGER: TEMP DISAB:
RETURN if the there is no pump/valve limiting flow
continuously through the boiler. If there is a pump/valve
limiting the flow through the boiler, the SETUP: AUX
FUNCTIONS: HEAT EXCHNAGER: TEMP DISAB: SYS
RET needs to be set. Then the Master boiler needs to set
SETUP: AUX FUNTIONS: HEAT EXCHNAGER: SEND
RETURN: to which of its return temperatures it would
send to all boilers. These include the Local Return
temperature or the System Return temperature.

The Member’s menu “SETUP: AUX FUNCTIONS: HEAT
EXCHNAGER: TEMP DISAB:” if set to RETURN or SYS
RET, will force the boiler to become unavailable to
HeatNet when the SETUP: AUX FUNCTIONS: HEAT
EXCHNAGER: TEMP< 140F. This value is adjustable to
135F if a forced air fan is used. When the SYS RET or
RETURN temperature is <140F the boiler responds to a
HeatNet Master’s request as” unavailable”. As soon as
the return temperature reaches 140F, the boiler will
respond to the Master’s request that it is available to fire.

If the Master boiler is a version 2 board, the Master will
always transmit its Local Return temperature to all
boilers. If the Master is set to Priority 1 and all other
non-condensing boilers are set to Priority 2, the Master
should always remain on if there is a call for heat. This
requires that the Priority 1 boiler be set up to start first
and stop last. Using this method should always send a
valid return temperature to the Member boilers. This
method can also be used with a version 3 board, but a
system return sensor is preferred.

When this condition is in effect, the STATUS * screen will
indicate “blr offline”. While the boiler is in this “not

SETUP & OPERATON HeatNet Control V3

Page 20

available” state, it can still be fired locally and failsafe is

still available.

SETUP: AUX FUNCTIONS: HEAT EXCHANGER:
SEND RETURN:

OFF The Master sends its return

temperature to all boilers

RETURN The Master sends its return

temperature to all boilers

SYS RET The Master sends the system

return temperature to all boilers

SETUP: AUX FUNCTIONS: HEAT EXCHANGER:
LOW TEMP:

OFF No check is made to the return

temperature – boiler remains
online

RETURN Uses the boilers own return

sensor (No pump /valve present)

SYS RETURN Uses the System Return temp

received from the Master Boiler
(its Local or System Return).

SETUP: AUX FUNCTIONS: HEAT EXCHANGER:
TEMP < 140F

Adjustable threshold temperature below which the
boiler will take itself offline.

1 degree F of hysteresis is provided so as to not
toggle offline<-to->online at the threshold temp.

Since the FIII boiler is non-condensing, the efficiency vs.
input is relatively flat. The MOD MAX value will not have
the same impact if the FIII non-condensing boilers were
placed in the Priority 1 set.

Futera III/ Fusion Boiler BTU Chart

In the Mixed Boiler System table (Figure 15) line 2
example, (2) CB/CW 500s are set as Priority 1 and (3)
MB/MW 1250s set as Priority 2. With a MOD MAX of
60%, each 500 can run to 300M (600M total) before a 1250
is called ON (Add Delay timer). Once both 500s are running
and the 1250 is called on and running, all (3) boilers will
drop to a total of the 600M BTUs: The sum of the 500, 500,
and 1250 would equal about 27% modulation: (.27 * 500M)
+ (.27 * 500M) + (.27 * 1.25MM) or: 135M +135M + 337M
= 607M and operate at higher combustion efficiencies: 27%
is roughly between the top two lines on the Typical
Efficiency of Condensing Boilers chart.

The Boiler System Response 5 chart illustrates how each
boiler (in the example) is brought on and fires to 60%, drops
to a lower fire rate and then adds the next boiler (vertical

dashed lines). Once all boilers are firing, the modulation is
released allowing all boilers to fire to 100%.

Figure 15 Boiler System Response 5

(2) CB/CW 500s, (3) MB/MW 1250s

So, for the first 600 MBTH of load, the combustion
efficiency is maximized by running the (2) fusion boilers
from low to middle input rates. Running the (2) fusion
boilers first also has the added effect of minimizing the
return water temperatures of <140F from reaching the
noncondensing boilers.

Figure 16 Futera III/Fusion Boiler Btu Chart (MBH)

MB/MW

CB/CW

500

750

1000

1250

1500

1750

2000

Max Input

500

750

1000

1250

1500

1750

2000

Min Input

4:1

125

188

250

312

375

437

500

Mod Max

80%

400

600

800

1000

1200

1400

1600

Mod Max

70%

350

525

700

875

1.05

1220

1400

Mod Max

60%

300

450

600

750

900

1050

1200

Mod Max

50%

250

375

500

625

750

875

1000

In summary, the system should be tuned using the boiler
selection charts and the MOD-MAX value so that boilers
are brought on and fired in their respective efficiency curve
while maintaining continuity in BTUs. Since selecting the
Priority 1 boiler is integral to the fault/offline tolerance of
the system, it is important to note any discontinuities in
BTUs if a Priority 1 boiler goes offline when multiple
Priority 1 boilers are used.

0.00

0.10

0.20

0.30

0.40

0.50

0.60

0.70

0.80

0.90

1.00

0 1,000,000 2,000,000 3,000,000 4,000,000 5,000,000

Input, %

System Load, Btu/Hr

Blr 1+2+3 (2250 MBTU)

Blr 1+2+3+4 (3500 MBTU)

Blr 1+2+3+4+5 (4750 MBTU)

SETUP & OPERATION HeatNet Control V3

Page 21

Figure 17 Mixed Boilers: Example: Condensing/Non-Condensing

CONTROL METHODS HeatNet Control V3

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Heating Control Methods

An overview of the (5) methods for controlling the Futera
III/Fusion series boiler are presented here. They are outlined
in more detail at the end of this section.

Heating Method 1

The first method is to use the Futera III/Fusion Series boiler
in its standalone modulating method. This method uses a
PID algorithm to maintain a setpoint and is enabled using
the HEAT DEMAND input. Closing a relay contact or
switch across the HEAT DEMAND input will cause the
Master boiler to control all Member boilers using H-Net.

Any standalone boiler will perform better
when controlling to a header sensor.

A Fusion, as a standalone boiler, requires a
header sensor to control properly.

A Member boiler may also be controlled by the HEAT
DEMAND input (LOCAL mode). The Member boiler will
then ignore commands from the Master and maintain its
LOCAL SETPOINT at the supply sensor.

Heating Method 2

The second method is to view the Futera III/Fusion boiler as
two separate boilers or as a HIGH/LOW boiler using T1 &
T2.

Heating Method 3

The third method is to allow a remote 4-20 mA or 0-10VDC
signal to control the setpoint of the boiler using the 4-20mA
input, along with the 4-20mA REMOTE ENABLE input.

Heating Method 4

The fourth method turns the boiler ON and OFF @ 100%
modulation using the AA terminal.

Heating Method 5

The fifth method uses an RS485 digital communications
cable with the MODBUS protocol. The boiler is controlled
by writing and reading registers using MODBUS
commands. A bridge module may also be used to convert
BACnet or LonWorks protocols to MODBUS.

Short cycling may occur when a firing rate is

sent to a Member boiler that would cause the
supply temperature to rise high enough to trip
the operating limit (low flow rate). After the
supply temperature falls, the boiler would
restart and the process may continue. A
Member boiler would use its supply (outlet)
sensor to protect itself from short cycling by
limiting the firing rate coming from the
Master. This occurs in the event that the
Member’s supply temperature increases
above the (OPERATE LIMIT- OPERATE
LIMIT BAND).

Operating Limit

When the Master boiler or an external control input is used
to control a Member boiler (i.e. AA, T1-T2, 4-20mA, H­Net), a software operating limit on the Member boiler will
be used to limit the maximum output of the Member boiler.
This operating limit can be adjusted in the SETUP:
SETPOINTS: OPERATING LIMIT.

There is also an associated operating limit band that must be
set in conjunction with the operating limit to help prevent
this LIMIT from being reached. Its purpose, is to limit the
output of the boiler as it approaches the operating limit. If
the band is set to 10 degrees, then for every degree that it
approaches the operating limit, the maximum output will be
lessened by 10%. With a band of 20 degrees, for every
degree that it approaches the band, the maximum output will
be lessened by 5%. You can think of this operating limit as
a smart aquastat which prevents the High Limit from
tripping. This method minimizes boiler short cycling when
using external inputs. The minimum setting is 1 degree and
effectively turns the limit band OFF. The default setting is
20F.

Input Priorities

The Futera III/Fusion-Series control inputs are prioritized
so that multiple levels of external control can be employed
at the same time. This means that if we are firing the boiler
with a low Priority input and a higher Priority input is called
for, the boiler will now fire at the higher Priority input.
When the high Priority input is removed, the boiler will
revert back to the lower Priority input that is still being
called.

Priority 1

The AA terminal has absolute control, and if used, will
always fire the boiler at 100% output, regardless of any
other input.

Priority 2

The HEAT DEMAND input is the next, and provides the
means to operate the boiler in LOCAL MODE when an

CONTROL METHODS HeatNet Control V3

Page 23

external control is not present, has failed, or needs to be
enabled or disabled. A Member can override the H-Net
commands using this input.

Priority 3

If a HeatNet (H-Net) Network cable is connected between
boilers, and one is configured as a MASTER (requires
HEADER sensor), then the MEMBER boilers will be
controlled over the network by the MASTER.

Priority 4

The 4-20mA/0-10VDC input in tandem with the 4-20mA
REMOTE ENABLE input is next. Any signal over 4.02mA
or 2.01VDC will start and operate the boiler if the
REMOTE ENABLE is closed.

Priority 5

The lowest Priority is using the boiler as (2) stages
HIGH/LOW. These are the T1 and T2 inputs.

Each of these control methods will now be explained in
more detail:

Heating Method 1
HEAT DEMAND

Closing a relay contact, switch, or jumper across the HEAT
DEMAND input will enable this method. This method
allows operation as a setpoint control. As a setpoint control,
the Master (defined by having a common system header
sensor), on the H-Net network can command the boiler fire
rate of all Member boilers. The Master can call as many
boilers that it has available (boilers are auto-detected over
the H-Net cable by the Master) to meet its SYSTEM
SETPOINT. The H-Net cable must be connected and will
cause the amber light on the communications board to flash.
The amber light indicates an H-Net Master is broadcasting
control information and a system heartbeat.

The AA terminal, the FAILSAFE mode active, 4-20mA at
PRIORITY: HIGHEST, and the HEAT DEMAND input
(LOCAL) on a Member, are the only inputs that will
override the H-Net control.

Figure 18 Heat demand input

MEMBER: Close to run at Local setpoint.
MASTER: Close to control all boilers and

run at System setpoint.

Master boiler

The MASTER boiler controls the system using a PID
algorithm. Once the boiler is started, a PID algorithm is
used to produce a modulation percentage value from 0­100%. This percentage is converted to a PWM, (P)ulse
(W)idth (M)odulation signal by each boiler. The
temperature of the water is maintained by sending this
PWM signal to the Variable Frequency Drive, which in turn
controls the blower motor. Since the main fuel valve is air­fuel coupled to the blower, the speed of the blower provides
the firing rate.

Member boiler(s)

A Member (lacking a common system supply header
sensor) boiler may also be controlled by the HEAT
DEMAND input (LOCAL mode). The Member boiler will
then ignore commands from the Master and maintain its
own LOCAL SETPOINT at its supply sensor. This can be
viewed as a manual override on a Member boiler. Be sure to
observe the proper use of a Common System Damper (See:
AUXILIARY FUNCTION OPTIONS section) and any
system pumps or system common interlocks.

Features of the HEAT DEMAND input include:

1. The control is designed to predict when to start and

stop the boiler and keep the setpoint in, or as close to
the control band as possible. If PREDICTIVE START
is enabled, the boiler may start when it is in the band
and not below it. This will help to maintain a more
accurate temperature relative to the setpoint. See also:
ADVANCED SETUP: FIRING MODE: PREDICTIVE
START: to disable this feature.

2. The control can also use the Outdoor Reset feature.

This feature allows the setpoint to be changed
automatically based on the outside air temperature. If
this feature is used, the control input: OR OVR
(OUTDOOR RESET OVERRIDE), can be used to
override the Outdoor Reset feature and run from the

local setpoint. A contact closure on the ‘AA’ input can

also override this method.

3. There is also support for a common system damper,

Heat Exchanger support, and starting the Master first
for common venting. For an overview of each of the
menu settings see: DEFAULT SETTINGS section.

Heating Method 2
STAGE Control T1-T2

The boiler can also be operated in 2 separate stages using
the inputs T1 and T2 inputs. Its intended use is with an
external stage controller with no analog or modulation
outputs. Closing only one of these contacts tells the boiler to
operate at MINIMUM FIRE.

CONTROL METHODS HeatNet Control V3

Page 24

Closing the other contact will fire the boiler at MAXIMUM
output (the same rate as closing the AA input).

Figure 19 Stage control inputs

The maximum output of the boiler is based on

the MAX VFD setting in the calibration mode
and not the nameplate rating.

The AA, HEAT DEMAND (LOCAL) input, the H-Net, the
4-20mA input will all override the stage control inputs.

Heating Method 3
4-20mA Control

Placing a current source between the + and – 4-20mA inputs
will allow remote control of the boilers setpoint. An
adjustable starting mA current signal here will start and then
fire the boiler. See: ADVANCED SETUP: 4-20mA
INPUT: CHANNEL MODE.

See section OPTIONAL FEATURES, Using the 4-20mA
input for extensive detail.

A 4-20mA signal will fire the boiler to the setpoint based on
the set parameters. . The input current signal is tabled with
the default parameters 4mA signal = 50 degrees F and
20mA signal = 200 degrees F. These (2) temperatures are
adjustable to provide a custom setpoint range. The
minimum start current is also adjustable between 3.71 and
5mAThe boiler start signal is 4.10mA. This will act as a
start/stop for the boiler if a jumper is placed on the 4-20mA
enable as an alternative to using a relay for enabling and
disabling.

The AA terminal, the HEAT DEMAND, and the H-Net
NETWORK are the only inputs that will override the 4­20mA input.

Heating Method 4
AA Input

HIGH FIRE input Control: The AA input will fire the boiler
at HIGH fire (maximum output of the boiler). No other
inputs can override this input. AA / High fire input.

Figure 20 Example: 4–20 mA connections

Method 4: Close this AA contact

to run the boiler at High Fire.

Heating Method 5
MODBUS communications

The fifth method uses an RS485 digital communications
cable with the MODBUS protocol to control the boiler
using the H-Net network. The Boiler or Boiler network will
run as in Method 1, but instead of the HEAT DEMAND
input, a software form of the HEAT DEMAND input is
used (40001: Boiler/System Enable/Disable). See:
MODBUS COMMUNICATIONS section.

Figure 21 MODBUS connections

Modbus Using

RJ45 Cat 5 cable

Modbus Using

shielded 3 wire.

Building

Management

Method 2

Stage Control Inputs:

T1 & T2

CONTROL METHODS HeatNet Control V3

Page 25

The System Setpoint Timer also needs to be loaded
periodically to allow the H-Net system to fallback to
Method 1 in the event communications is lost from the
Building Management System (BMS).

This feature can be turned off in ADVANCED SETUP:
COMMUNICATIONS: SETPOINT TIMER: OFF. If the
setpoint timer feature is set to ON, the ADVANCED
SETUP: COMMUNICATIONS: SETPOINT TIME may be
set to a time that allows any write to a MODBUS register to
reset the setpoint timer as long as it occurs within that time.
This will reset the setpoint timer without writing the
setpoint timer register. So, periodically writing the setpoint
register will automatically reset the setpoint timer as long as
the write occurs within that time window. The MODBUS
protocol allows writing and reading registers using
MODBUS commands.

Protocessor option

An optional BACnet or LonWorks bridge module can be
used to connect the MODBUS network to a BACnet or
LonWorks network. Use communications default settings.

Figure 22 Protocessor bridge module option

This method allows enabling and disabling the boiler or H­Net system, changing setpoints, reading boiler(s) status, or
temperatures remotely using digital commands. See the
section: MODBUS Communications.

Base Loading, Relay Control

The H-Net control has the ability to control (1) base load
boiler using the K8 Relay contacts on J4 pins 2 & 6. In
order to connect to this plug, (2) wires with pins are
required and inserted in J4. Base Loading via relay requires
these (2) flying leads (loose wires available from the
factory) to be inserted into J4, pins 2 & 6. These (2) wires
then make up the Normally Open contacts. This feature can
be used on Master or Member boilers. The solid state relay
K8, with contact connections on J4.2 & J4.6 has a rating of:

0.1 to 1 Amp.

If the base load boiler is of the modulating type, a 4-20mA
signal is also provided on J4 pins 1 and 5. Jumper shunt JS1
will then need to be set to 4-20mA position. Two additional
wires (available from the factory) will need to be added to
the J4 pins at 1 & 5. Pin 1 is the + output of the 4-20mA
transmitter, and pin 5 is the – output. This modulating
control signal is used to modulate the base load boiler along
with the HeatNet boilers in parallel. The ADAPTIVE MOD
does not function in lowering the modulation rate when the
base load boiler is added. The PID will adapt to the newly
fired base load boiler and lower its modulation rate when
the increase in water temperature is observed.

Figure 23 Base loading with Futera II boiler

CONTROL METHODS HeatNet Control V3

Page 26

Figure 24 Base loading with Dominator boiler

Enable the base load feature by setting:

ADVANCED SETUP: SYSTEM: OPTION to BASE
LOAD. This setting the OPTION Relay to be used as

control for a Base Load Boiler.

1. ADVANCED SETUP: SYSTEM: OPTION to BASE

LOAD. This setting the OPTION Relay to be used as
control for a Base Load Boiler.

2. The ADVANCED SETUP: BASE LOAD BOILERS:

BASE LOAD BOILERS: to 1. Currently allows (1)
base load boiler.

3. The START & STOP qualifier condition to the method

discussed below.

4. The DELAY TIME to the amount of time required

after the start qualifier condition has been met to start
the boiler.

If a MINIMUM OFF time of the Base Load boiler is
needed, the Base Load boiler will share the MIN OFF TIME
of the boiler controlling it. If the base load boiler was
running and shuts off, the MIN OFF TIME will need to
expire before the boiler can start again. Once this time
expires, the DELAY TIME also needs to expire to start the
boiler. This will help in minimizing short cycle conditions
and can be set at: ADVANCED SETUP: FIRING MODE:
MODE: MIN OFF TIME.

Preferred:

A modulating base load boiler that can accept a 4-20mA
control is preferred or a non-modulating base load boiler

that is sized correctly to the H-Net boilers. Consider the
Futera II or the Dominator series for the Base Load role.

If the base load boiler is not of the modulating type,
stopping the Base Load boiler will require that the size of
the Base Load boiler in BTUs to be known relative to the
HeatNet boilers. Boiler selection is ideally; having more
total BTUs in the HeatNet boilers than total BTUs of the
Base Load boiler. This will prevent short cycling. Example:
(4) 2 million BTU HeatNet boilers = 8 million BTUs and
(1) 6 million BTU Base Load boiler.

When all (4) HeatNet boilers are running @ 95%, the Base
Load boiler is called on (demand is approx. 8 million
BTUs). As the Base load boiler comes on it introduces 6
million BTUs and the HeatNet boilers modulate down to
25% for a total output of 2 million BTUs and running at
high efficiency. The HeatNet boilers can now modulate to
the load from 1.6 million BTUs (20% mod) to another 8
million BTUs.

Not Preferred:

Example of having a larger Base Load boiler that is not of
the modulating type: If there is a 6 Million BTU Base Load
boiler running with (3) 2 million BTU HeatNet boilers, a
short cycling situation will arise when the (3) 2 million BTU
boilers are running @ 95% and the Base Load boiler is
called on. At this point there is a need for approximately 6
million BTUs. The (3) smaller boilers will then modulate
down to low fire. At this point, the (3) smaller boilers need
to shut off or the Base load boiler would need to shut off.
There is no overlap. A selection for stopping the boiler now
needs to be determined. Setting the Stop qualifier;
Modulation to 40% or a low fire rate will shut the Base
Load boiler off and allow the (3) smaller boilers to modulate
up again (short cycle of the Base Load boiler; Use the Delay
Timer and Min OFF timer). The Stop qualifier; OA T > xxF
may also be used if the system design temperature is known.
Then let the Base Load boiler cycle off of its limits, whether
a 2 stage, Hi/Lo, or modulating boiler. The default setting is
for the Base Load boiler to stop first once the water
temperature exceeds the top of the heating band

.

CONTROL METHODS HeatNet Control V3

Page 27

Figure 25 Base loading relay

CONTROL METHODS HeatNet Control V3

Page 28

Setting up base loading

The base load boiler is controlled using a set of contacts to
enable it (location J4). Enabling/Disabling this relay contact
can be done using any combination of (3) qualifiers to start
the boiler and (4) to stop the boiler. These qualifiers are:

1. Modulation %:
a. START menu item: The relay contact will close

when the MOD % from the Master boiler exceeds
this value. ADVANCE SETUP:BASE LOADING:

START>MOD

b.

STOP menu item

: The relay contact will open
when the MOD % from the Master boiler falls below
this value.

ADVANCE SETUP:BASE LOADING:

STOP<MOD

If the START>MOD value is set to a value

higher than the ADVANCED SETUP: MOD-
MAX: all boilers will be firing before this
modulation rate is reached. This will ensure
that all available boilers are firing before the
base load boiler relay is enabled.

c. Setting the: STOP<MOD to a % value slightly

above the min fire rate % of the system will ensure
that the base load boiler will stop before the first
condensing boiler stops. This is due to the
Modulation rate being close to the min modulation
rate before the water temperature exceeds the top of
the heating band.

2. Outside Air Temperature:
a. START menu item: The relay contact will close to

enable the boiler when the OA T read from the
Outside Air Temperature sensor (if equipped) falls
below this temperature. ADVANCE SETUP:BASE

LOADING: START< OA T

b. STOP menu item: The relay contact will open to

disable the boiler when the OA T read from the
Outside Air Temperature sensor (if equipped) rises
above this value. ADVANCE SETUP:BASE

LOADING: STOP> OA T

If the OA T qualifier is used as the Start and

Stop qualifier, ensure that there is at least a few
degrees difference for hysteresis. Return Water
Temperature

c.

START menu item

: The relay contact will close to
enable the boiler when the RET read from the Return
Water Temperature sensor (if Equipped) falls below
this temperature.

ADVANCE SETUP:BASE

LOADING: START> RET

d.

STOP menu item

: The relay contact will open to

disable the boiler when the RET temperature read

from the Return Water Temperature sensor (if
Equipped) rises above this temperature.

ADVANCE

SETUP:BASE LOADING: STOP< RET

3.

FIRST

:

a.

STOP menu item

: The relay contact will open to
disable the boiler when the temperature exceeds the
heating band. This gives the result of stopping the
Base Load boiler First. Default setting.

Delay time

The DELAY TIME is also included to hold off starting the
boiler until the delay time is met. Once the start condition
qualifier term is met, the DELAY TIME will start counting
down. When the time expires, the base load relay contacts
will close. ADVANCE SETUP: BASE LOADING:

DELAY TIME. It is adjustable in a range of: 0 to 60 minutes.

Base Load Failsafe

If:

1) There are no boilers available to fire (offline or

faulted).

2) There are no boilers in local override.

3) There is a call for heat.

The J4 Base Load relay will close.

If a boiler becomes available and needs to fire, the Base Load
boiler will remain firing until the temperature exceeds the
band. This is provided to keep the system from entering a no
heat situation.

If there are no boilers available to fire (offline or faulted) and
there are no boilers in local override, and there is a call for
heat, The J4 Base Load relay will close. If a boiler becomes
available and needs to fire, the Base Load boiler will remain
firing until the temperature exceeds the band. This is provided
to keep the system from entering a no heat situation.

Domestic Hot Water Methods

Domestic Hot Water control is supported using (6) methods.
When using the Domestic Hot Water methods, the wire
jumper, JPS1 on each control board providing Domestic Hot

Water, must be cut to limit the boiler’s maximum output

temperature to 200F. Refer to Figure 26 for control input,
refer to Figure 57 for sensor inputs, and Figure 45 for pump
output locations.

CONTROL METHODS HeatNet Control V3

Page 29

Figure 26 Jumper JPS1

Most of these methods use a separate PID

control for the DHW. This means that the Master
boiler can be used to individually control its own DHW tank
and provide space heating functionality at the same time.

A MASTER TYPE is required when using DHW. Its setting
is located under the DISTRIBUTED CTRL menu. Any time
its setting is changed, a power cycle is required. The menu
choices are:

AUTO: will handle normal heating only applications. It
may also be used when Member boilers have tanks
connected and are controlled with the DHW BOILER: set
to LOCAL.

DHW: is for DHW applications without space heating.

COMBO: Will allow combination Space and DHW

heating control of boilers by the Master.

The OR OVR input now functions in many of the methods as
a DHW Heat Demand input (except DHW Heating Only
method), but still retains the original OR OVR functionality in

AUTO, if the DHW menus are not used (DHW BOILER?
NO). If the DISABLE TO CHANGE message appears,
remember to remove the any call for heat including the OR
OVR input.

When the MASTER TYPE is set to COMBO (Combination)
the MODULAR BOILER SET menu will contain (2)
separate menus for controlling the ADD BOILER DELAY,

SHED BOILER DELAY, MODULATE DELAY, and the
MOD MAX. This allows the independent control of boilers

for each of the (2) PIDs.

When using MASTER TYPE: COMBO, the Master may
control DHW and Space Heating needs. If the Master goes

down or loses communication with the Member, a Failsafe
mode is available to provide temporary heat.

The DHW Failsafe mode is active when a Member boiler’s

SETUP: AUX FUNTIONS: FAILSAFE MODES: H-NET
COMM LOST: is set to ON. When this is set to on, normal

DHW heating using the OR OVR or DHW sensor is disabled,
even though there may be a DHW call on one of these inputs.

When the Master Boiler’s communication is lost, and after 10
minutes of not being restored, the DHW inputs become
active. The boiler now enters a standalone mode. The Heat
Demand on that boiler becomes active and not only runs to
provide failsafe space heating, but DHW heat as well. The
STATUS screen will display an ‘*’ and H-NET LOST. If a
thermostat is used, the boiler will run to Method 5A until the
thermostat input removes the DHW call. If a DHW
temperature sensor is used, the boiler will modulate to
maintain tank temperature. The DHW Call always has priority
over space heating. A dual 10k sensor is available that can be
wired from one tank to two boilers.

The Failsafe boiler needs to either have a thermostat input
from a DHW tank or a temperature sensor connected to a
tank. When these sensors are connected normally, they would
override any call to the boiler by the Master (when in

SETUP: DOMESTIC HOT WATER: DHW BOILER:
COMBO) and enter a DHW heating mode. With the Failsafe

active, this function is inhibited and the Failsafe boiler only
responds to these inputs with the loss of the Master’s
communication.

For more details see DHW Method 2: Failsafe Combination
DHW and Space Heating with a MASTER Boiler and
MEMBER Boilers page 34.

DHW Maximum Runtime

When a Combination system has a call for DHW heat and
services it for a time that is longer then designed, the DHW
may need to be locked out or held off for a predetermined
amount of time (retry).

Two settings are provided to control this situation: the
Maximum Runtime, and the Holdoff Time. The Maximum
Runtime is set to allow the DHW call to occur for the design
time of the system. If for some reason this time is exceeded,
the Holdoff Time setting goes into effect. The Holdoff time
can be set to a Lockout (the OR OVR input needs to toggle or
a power cycle to clear the Lockout), or a fixed amount of
boiler off time. If the fixed amount of Holdoff time is
selected, the DHW functionality will be cycled between the
boilers running for the Maximum Runtime, and stopped for
the duration of the Holdoff Time.

DHW METHODS HeatNet Control V3

Page 30

DHW Method 1: DHW Heating ONLY using a DHW MASTER and MEMBER
Boiler(s) Employing H-Net

Figure 27 Example DHW Only, Reverse Return Piping – Method 1.

MASTER

MEMBER 2

MEMBER 3

HNETHNET

Tank Sensor

DHW Sensor

Ball Valve

Expansion T ank

Pressure

Reducing

Cold Water

Makeup

Backflow

Prevention

Local Pump

Local Pump

Domestic

Supply

Domestic

Supply

WM

Water Met er

HeatNet

HeatNet

Local Pump

HeatNet

Make

Up

Make

Up

DHW METHOD 1: DHW Heating ONLY using a DHW MASTER, Multiple Non-Condensing Boilers

A DHW Setpoint is maintained in the DHW tank based on the MASTER’s DHW Sensor. The system pump is enabled when the

boiler’s Heat Demand input is closed. Boilers are staged to meet the DHW Setpoint in the tank based on their runtime, and each

boiler will enable its local pump when it is running. The MASTER modulates the boilers to maintain the setpoint in the tank.

The cold water make up is piped into the supply piping to reduce the possibility of condensing in the boilers.

DHW METHODS HeatNet Control V3

Page 31

Figure 28 DHW Method 1 Quick Start Settings

DHW METHOD 1: DHW Heating ONLY Using a DHW MASTER and MEMBER Boiler(s).

MASTER (DHW Only)

Settings

DHW Use Sensor

HeatNet Address

MASTER Type

Combustion Air Damper

Yes

Automatic

DHW Only

Off

Inputs

Local/Remote

DHW Sensor

JPS1 Jumper must be cut to service DHW

Local

Yes - Tank

Outputs

Local Pump On

When Boiler Running

MEMBER 2

Settings

HeatNet Address

Combustion Air Damper

2

Off

Inputs

Local/Remote

JPS1 Jumper must be cut to service DHW

Remote

Outputs

Local Pump On

When Boiler Running

MEMBER 3

Settings

HeatNet Address

Combustion Air Damper

3

Off

Inputs

Local/Remote

JPS1 Jumper must be cut to service DHW

Remote

Outputs

Local Pump On

When Boiler Running

The example drawings in this section are simplified. They are meant to illustrate connections to the HeatNet V3
control. Only major components are illustrated.

The system engineer must ensure additional safeties, piping, maintenance valves, and components meet code requirements and
safe operation.

DHW METHODS HeatNet Control V3

Page 32

This method requires a 10k thermistor connected to the
DHW Sensor input of a DHW MASTER, or a standalone
boiler, and a DHW tank. This method does not use a
HEADER sensor. The DHW temperature is maintained by
the space heating PID for backwards compatibility. With
this method the OR OVR input does not function as a DHW
enable and is not used. The Heat Demand input is used to
enable/disable DHW heating operations.

The System pump is enabled on the MASTER as long as the
Heat Demand input is closed. The selected network boiler’s
Local pump is engaged when there is a call for DHW
heating by the MASTER. This allows for a DHW
loop/buffer and A DHW tank that can be heated using the

MASTER’s DHW pump (Reverse/Return only) or each

boiler’s Local Pump/Valve supplying this loop/buffer.

Boilers are started as long as the tank’s water temperature is

below the (DHW SETPOINT – LOWER BAND). The first
boiler is started immediately. The next boiler(s) is started
after the ADD BOILER DELAY time expires. Boilers are
not added when the temperature is above the (DHW
SETPOINT – LOWER BAND) and below the UPPER
BAND. Once the UPPER BAND is exceeded, boilers will
shut off based on the SHED BOILER DELAY TIME.
Setting up this method is done via the menu in:

SETTINGS: DOMESTIC HOT WATER.

Connect a 10k thermistor from the DHW tank’s sensor
well to J10B terminals on the DHW MASTER, or
standalone boiler. Wire a pump or valve from the Local
pump of each DHW boiler.

A DHW call is when the DHW temperature is
below the (DHW SETPOINT – LOWER BAND)
or when the DHW temperature is below the (DHW
SETPOINT + UPPER BAND) and boilers are
firing.

The Masters System pump (Normally Open) will
always be enabled as long as the Heat Demand
input is closed.

The MASTER’s DHW pump (Normally Open)
relay contacts will close during a DHW call. Once
the call has ended, the last DHW boiler stops firing,
and the programmed post-purge time has expired,

the MASTER’S DHW contacts will open. In this

application the Masters DHW pump can be used
globally.

After a DHW call ends the Local pump will remain
on during a post purge pump cycle until the post
purge timer expires.

DHW Only Method 1 Set Up:

1. Enter the DOMESTIC HOT WATER menu on

the MASTER boiler. In the BOILER MODE
selection, enter DHW ONLY. The MASTER uses

this method as a DHW system much like a space
heating system.

MEMBER boilers may set the BOILER MODE to
LOCAL and go offline to perform secondary DHW
heating, but the MASTER setting must be set to
AUTO/OFF.

Setting the BOILER MODE to COMBINATION
using this method may cause erratic operation and the
DHW pump to not be enabled.

2. Change the DHW SETPOINT to the desired target

temperature of the water in the tank. Once the control
determines there is a call for DHW, the DHW
SETPOINT is loaded and the MASTER boiler will
target the setpoint.

3. Now, change the LOWER BAND to the desired

temperature (DHW SETPOINT – LOWER BAND)
below which boilers are to be added. This setting
corresponds to the minimum water temperature
required in the tank. DHW heating will be initiated

when the DHW tank’s water temperature is below the

temperature (DHW SETPOINT – LOWER BAND).

How long the temperature of the tank stays below the
temperature (DHW SETPOINT – LOWER BAND) is
used to determine when boilers are started along with
the ADD BOILER DELAY TIME.

4. Next, change the UPPER BAND to the desired

temperature (DHW SETPOINT + UPPER BAND)
above which boilers are to be shed. This setting is the
maximum tank temperature. Setting the SHED
BOILER DELAY TIME correctly will limit the
maximum tank temperature to the (DHW SETPOINT
+ UPPER BAND). Setting the SHED BOILER
DELAY TIME = 0 will shut off all boilers
immediately once the (DHW SETPOINT + UPPER
BAND) is exceeded.

5. Now, determine if the DHW Priority is required by

the menu item PUMP PRIORITY?. Setting this
value to YES will turn OFF the system pump when
the DHW mode is active. Setting this value to NO
leaves the system pump on.

6. Select the amount of time for the POST PURGE of

the DHW pump. This is the time that the MASTER’S
DHW pump relay remains energized after the DHW
SETPOINT has been satisfied.

A. The Local pump will remain on during a post

purge pump cycle until the post purge timer
expires.

DHW METHODS HeatNet Control V3

Page 33

B. The System pump on the MASTER boiler

functions as a global pump and remains on as
long as the heat demand is enabled.

C. The DHW pump will remain on until the last

boiler on the network has stopped firing and the
post-purge time has expired.

7. Now, in order to be a MASTER boiler, it must have a

Header sensor. In method 1, DHW Only, we will
employ the DHW sensor (J10-A, 9 & 10) in this
system instead of a Header sensor. USE SENSOR in
this example will be set to YES. This will allow the
boiler to control the DHW tank or system loop
temperature as a MASTER boiler using the DHW
sensor. The upper and lower differential temperatures
will also be loaded.

8. The SHARING function is not applicable in “DHW

Only” set-up.

9. Set the LOCAL PUMP OFF: value to NO. This will

leave the local pump on during a DHW heating cycle
(backwards compatibility).

Setting this value to YES, will shut the local pump
off during a DHW heating cycle, but will keep the
local pump on for the LOCAL DELAY: 10s time
before shutting off. This LOCAL DELAY: time
can be adjusted in the next menu item by pressing
the down arrow again.

The MASTER’s DHW relay will remain on as long

as there are boiler’s firing and the DHW

temperature is below the (DHW SETPOINT +
UPPER BAND). Once all boilers are off and the
DHW temp is equal to or above the (DHW
SETPOINT + UPPER BAND), the DHW pump
will begin its post-purge time. If during this post­purge time the DHW temp falls below the (DHW
SETPOINT + UPPER BAND), the DHW pump
will remain on.

10. Menu item: PURGE TO: will be displayed.

Set the PURGE TO: setting to TANK. This will
purge the heat from the boiler into the tank or
system loop. This will be done using the DHW
pump after the DHW heating cycle is complete.

If the PURGE TO: is set to SPACE, once the
DHW cycle has completed, the MASTER will shut
the DHW pump off within a few seconds. The

SPACE setting should only be used for
COMBINATION and DHW LOCAL heating.

Now in the,

SETTINGS: DISTRIBUTED CONTROL:
MASTER TYPE select DHW Only.

JPS1 MUST be cut on all boilers

providing DHW.

DHW METHODS HeatNet Control V3

Page 34

DHW Method 2: Failsafe Combination DHW and Space Heating with a MASTER
Boiler and MEMBER Boilers Utilizing Valves (MASTER Type: Combination)

Figure 29 In this example the MASTER is not a DHW boiler.

Member 2

Cold Wate r

Makeup

Expansion T ank

Backflow
Prevention

Pressure

Reducing

Ball Valve

Local Pump

Member 3

Master

Domestic Hot

Water

Supply

Make

Up

Dual

Tank Sensor

WM

Water Met er

3-Way
Valve

DHW Valve

DHW Valve

Local Pump

Local Pump

DHW Sensor

System Pum p

Heating

Only

Combination

Failsafe

Heating

Combination

Failsafe

DHW

Outdoor Air S ensor

Outdoor Air S ensor

System Return

System Header Sensor

System Return Sensor

System Pum p

MIN 3X PIPE DIAMETERS

MAX 10X PIPE DIAME TERS

BETWEEN CENTERS

System Supply

DHW Sensor

3-Way

Valve

System Pum p

System Pum p

Supply Retu rn Sensor

HeatNet

Supply Hea der Sensor

HeatNet HeatNet

DHW METHOD 2: Failsafe Combination DHW and Space Heating using a MASTER Boiler and MEMBER boilers with
valves

In this method the MASTER simultaneously controls both space heating and DHW heating. The MASTER is piped to only
service space heating, and both MEMBERs are piped to service space heating and DHW heating. The MASTER’s Heat Demand
input enables space heating by energizing the system pump and maintaining the Heating Setpoint at the System Header Sensor.
The MASTER’s OR OVR input enables the DHW heating, by maintaining the DHW Setpoint at the DHW Sensor located in the
DHW tank.

Boilers are staged to meet both the Space Heating Setpoint, and the DHW Setpoint based on their runtime. When a boiler is fired
to service a space heating demand it will enable its local pump, and when a boiler is fired to service a DHW demand it will enable
its local pump and enable its DHW valve to divert water to the tank. The MASTER modulates the boilers in order to maintain the
setpoints.

This method allows for a MEMBER boiler to provide Failsafe mechanisms in the event the MASTER fails and stops
communicating to the MEMBERs. MEMBER 2 is configured to provide failsafe space heating, and MEMBER 3 is configured to
provide both failsafe space heating and failsafe DHW heating.

DHW METHODS HeatNet Control V3

Page 35

Figure 30 DHW Method 2 W/Diverting Valves Quick Start Settings

DHW METHOD 2: Combination DHW and Space Heating Using a MASTER Boiler and MEMBER Boiler(s) Employing
Diverting Valves.

MASTER (Space Heating Only W/Valves)

Settings

MASTER Type

HeatNet Address

DHW Use Sensor

Combustion Air Damper

Combination

Automatic

Yes

Off

Inputs

Local/Remote

OR/OVR

Header Sensor

System Return

DHW Sensor

Local

Jumper

Yes

Optional

Yes - Tank

Outputs

System Pump On

Local Pump On

When Boiler Enabled

When Boiler Running

MEMBER 2 (Space Heating Or DHW, Failsafe Space Heating W/Valves)

Settings

HeatNet Address

DHW Boiler Mode

DHW Local Pump Off

Combustion Air Damper

HeatNet Failsafe

2

Combination

No

Off

On

Inputs

Local/Remote

JPS1 Jumper must be cut to service DHW

Remote

Outputs

System Pump On

Local Pump On

DHW Pump On

Failsafe Heating

When Boiler Running

DHW Call

MEMBER 3 (Space Heating Or DHW, Failsafe Space Heating and DHW W/Valves)

Settings

HeatNet Address

DHW Boiler Mode

DHW Local Pump Off

Combustion Air Damper

HeatNet Failsafe

3

Combination

No

Off

On

DHW Use Sensor

System Pump Priority

Yes

No

Inputs

Local/Remote

OR/OVR

DHW Sensor

JPS1 Jumper must be cut to service DHW

Remote

Jumper

Yes - Tank

Outputs

System Pump On

Local Pump On

DHW Valve On

Failsafe Heating

When Boiler Running

DHW Call

DHW METHODS HeatNet Control V3

Page 36

DHW Method 2: Failsafe Combination DHW and Space Heating with a MASTER
Boiler and MEMBER Boilers Utilizing Pumps (MASTER Type: Combination)

Figure 31 In this example the MASTER is not a DHW boiler.

DHW Pump

DHW Pump

Member 2

Cold Water

Makeup

Expansion T ank

Backflow

Prevention

Pressure

Reducing

Ball Valve

Local Pump

Member 3

Master

Local Pump

Domestic Hot

Water

Supply

Make

Up

Dual

Tank Senso r

WM

Water Met er

Local Pump

Outdoor Air S ensor

Heating

Only

Combination

Failsafe

Heating

Combination

Failsafe

DHW

System Pum p

System Return

System Heade r Sensor

System Return Se nsor

System Pum p

MIN 3X PIPE DIAMETERS

MAX 10X PIPE DIAME TERS
BETWEEN CENTERS

DHW Sensor

DHW Sensor

System Pum p

System Pum p

System Supply

HeatNet

Supply Head er Sensor

HeatNet

HeatNet

Supply Ret urn Sensor

DHW METHOD 2: Failsafe Combination DHW and Space Heating using a MASTER Boiler and MEMBER boilers with
pumps

In this method the MASTER simultaneously controls both space heating and DHW heating. The MASTER is piped to only
service space heating, and both MEMBERs are piped to service space heating and DHW heating demands. The MASTER’s
Heat Demand input enables space heating by energizing the system pump and maintaining the Heating Setpoint at the System
Header Sensor. The MASTER’s OR OVR input enables the DHW heating, by maintaining the DHW Setpoint at the DHW
Sensor located in the DHW tank.

Boilers are staged to meet both the Space Heating Setpoint, and the DHW Setpoint based on their runtime. When a boiler is fired
to service a space heating demand it will enable its local pump, and when a boiler is fired to service a DHW demand it will enable
its DHW pump. The MASTER modulates the boilers in order to maintain the setpoints.

This method allows for a MEMBER boiler to provide Failsafe mechanisms in the event the MASTER fails and stops
communicating to the MEMBERs. MEMBER 2 is configured to provide failsafe space heating, and MEMBER 3 is configured to
provide both failsafe space heating and failsafe DHW heating.

DHW METHODS HeatNet Control V3

Page 37

Figure 32 DHW Method 2 W/Pumps Quick Start Settings

DHW METHOD 2: Combination DHW and Space Heating Using a MASTER Boiler and
MEMBER Boiler(s) Utilizing DHW Pumps.

MASTER (Space Heating Only W/Pumps)

Settings

MASTER Type

HeatNet Address

DHW Use Sensor

Combustion Air Damper

Combination

Automatic

Yes

Off

Inputs

Local/Remote

OR/OVR

Header Sensor

System Return

DHW Sensor

Local

Jumper

Yes

Optional

Yes - Tank

Outputs

System Pump On

Local Pump

When Boiler Enabled

When Boiler Running

MEMBER 2 (Space Heating Or DHW, Failsafe Space Heating W/Pumps)

Settings

HeatNet Address

DHW Boiler Mode

DHW Local Pump Off

Combustion Air Damper

HeatNet Failsafe

2

Combination

Yes

Off

On

Inputs

Local/Remote

JPS1 Jumper must be cut to service DHW

Remote

Outputs

System Pump On

Local Pump On

DHW Pump On

Failsafe Heating

When Boiler Running

DHW Call

MEMBER 3 (Space Heating Or DHW, Failsafe Space Heating and DHW W/Pumps)

Settings

HeatNet Address

DHW Boiler Mode

DHW Local Pump Off

Combustion Air Damper

3

Combination

Yes

Off

HeatNet Failsafe

DHW Use Sensor

System Pump Priority

On

Yes

Yes

Inputs

Local/Remote

OR/OVR

DHW Sensor

JPS1 Jumper must be cut to service

DHW

Remote

Jumper

Yes - Tank

Outputs

System Pump On

Local Pump On

DHW Pump On

Failsafe Heating

When Boiler Running

DHW Call

DHW METHODS HeatNet Control V3

Page 38

This Method highlights the flexibility of the HeatNet
system. It works much the same as DHW METHOD 1, but
also has the ability to provide space heating and failsafe
functions. With a three boiler system, and with any one
boiler down, the system can still provide space heating and a
DHW call seamlessly.

With this method the MASTER boiler will use two PID
controls to simultaneously maintain the DHW and space
heating setpoints. This method is determined by

SETTINGS: DISTRIBUTED CONTROL: MASTER
TYPE: COMBINATION.

This method utilizes a 10k thermistor connected to the
DHW Sensor input and the HEADER sensor input of a
MASTER boiler. Setting up the DHW portion of this
method is done via the menus in: SETTINGS: DOMESTIC
HOT WATER. For information on setting up the space
heating portion of this method, Refer to Heat Demand
Control Method 1 located in the CONTROL METHODS
section.

When this method is used (due to use of the DHW sensor),
the OR OVR input functions as an enable/disable. This
allows the DHW heating function to be enabled or disabled
much in the same way as the Heat Demand input for space
heating.

The MASTER does not use its pump globally when any
DHW boiler is called. The DHW pump is individually
controlled on each boiler that fires in DHW.

When using this method, a DHW band is also available in
the Home screen. The space heating band will be displayed
on the left and the DHW Heating band on the right.

When using MASTER TYPE: COMBINATION, the

MASTER will control DHW and Space Heating needs. If the
MASTER goes down or loses communication with the
MEMBER, a Failsafe mode is available to provide temporary
heat.

The DHW Failsafe mode is active when a MEMBER

boiler’s SETTINGS: FAILSAFE MODES: H-NET
COMMUNICATIONS LOST: ON. When this is set to on,

normal DHW heating using the OR OVR or DHW sensor is
disabled, even though there may be a DHW call on one of
these inputs.

When the MASTER Boiler’s communication is lost, and
after 10 minutes of not being restored, the DHW inputs
become active. The boiler now enters a standalone mode. The
Heat Demand on that boiler becomes active and not only runs
to provide failsafe space heating, but DHW heat as well. The
STATUS screen will display H-NET LOST.

If a thermostat is used, the boiler will run to Method 5A until
the thermostat input removes the DHW call. If a DHW
temperature sensor is used, the boiler will modulate to
maintain tank temperature. The DHW Call always has
Priority over space heating. A dual 10k sensor is available
that can be wired from one tank to two boilers.

The DHW Method 2 examples uses (3) boilers. The
MASTER controls the Space and Domestic needs, though it
is not a DHW boiler. Failsafe control is provided by wiring
the MEMBER boiler to the tank sensor (dual sensor is
optional) and any other system control needs the MEMBER
may require in its backup role. Then one of the local DHW
control methods can be used to implement DHW heating.

One advantage to this configuration is that a BMS can
control the system through the MASTER. It can also
monitor system status through a central location (MASTER
boiler) by a BMS, or HeatNet Online. This failsafe method
can also be used in Combination DHW/Space Heating.

Set up the MASTER boiler first:

1. Connect a 10k thermistor from the DHW tank’s sensor

well to J10B terminals on the MASTER, and connect a
Header Sensor to the SYSTEM HEADER input. Wire
any pump or valve from the DHW Pump relay’s
(normally open) contact to control flow of the heating
water into the tank’s coil or DHW loop.

2. Now, set the SETTINGS: DISTRIBUTED

CONTROL: MASTER TYPE: to COMBINATION.
This setting informs the HeatNet control that (2) PIDS
are to be used to control DHW and space heating.

3. There are two MODULAR BOILER menus, one for

space heating and one for DHW heating. These (2)
menus appear when the SETTINGS: DISTRIBUTED

CONTROL: MASTER TYPE is set to
COMBINATION. The (2) Modular boiler settings are

located in the SETTINGS: MODULAR BOILER:
menu. Normally, there is only one, but with (2)
independent PIDs, the (2) heating setpoints may behave
differently due to their loads or for other various
reasons. These allow for separate ADD, SHED,

MODULATE DELAY TIME, and MODULATION
MAXIMUM settings for DHW and space heating.

4. Next, enter the SETTINGS: DOMESTIC HOT

WATER menu. When prompted for BOILER MODE

enter AUTO.

5. Change the DHW SETPOINT to the desired target

temperature of the water in the tank/ or DHW loop.
Once the control determines there is a call for DHW
heat, the DHW PID will target this SETPOINT.

6. Now, change the LOWER BAND to the desired

temperature (DHW SETPOINT – LOWER
BAND) below which boilers are to be added.
This setting corresponds to the minimum water
temperature required in the tank. DHW heating
will be initiated by starting boilers when the

DHW tank’s water temperature is below the

temperature (DHW SETPOINT – LOWER
BAND).

7. Next, change the UPPER BAND to the desired

temperature (DHW SETPOINT + UPPER
BAND) above which boilers are to be shed. This

DHW METHODS HeatNet Control V3

Page 39

setting is the maximum tank temperature. Setting
the SHED BOILER DELAY TIME correctly will
limit the maximum tank temperature to the
(DHW SETPOINT + UPPER BAND). Setting
the SHED BOILER DELAY TIME = 0 will shut
off all boilers immediately once the (DHW
SETPOINT + UPPER BAND) is exceeded.

8. Change the DHW Priority menu item PUMP

PRIORITY. Setting this value to YES will turn OFF
the system pump when the DHW mode is active.
Setting this value to NO leaves the system pump on.
This time includes the DHW post purge of the DHW
pump/valve.

9. Go to the POST PURGE menu item. This is the time

that the DHW pump relay remains energized after the
DHW SETPOINT has been satisfied. Once the tank
has exceeded the DHW SETPOINT + UPPER BAND
temperature and this DHW boiler has shut off (DHW
SHED BOILER DELAY TIME), the post purge time
will begin.

10. Now, go to USE SENSOR Select YES. This will

allow the boiler to control the tank or DHW loop
temperature using the DHW sensor. The upper
and lower band temperatures will also be loaded
when set to YES.

11. The next menu is the SHARING menu. Sharing

determines what happens when a DHW boiler is needed
and none are available (all boilers are running in space
heating and DHW heating). This means the MASTER
needs to steal a space heating boiler that is running or
no more boilers can fire in DHW.

OFF Is first come first serve. If a Boiler is not available

because all boilers are firing a space heating
demand, the DHW firing algorithm waits until
one becomes available. If a space heating boiler is
needed, a DHW running boiler cannot be stolen
for space heating. Priority goes to the first

demand present.

CYCLE The DHW algorithm can steal a space heating

boiler and fire it as a DHW boiler. The space
heating boiler stops and then restarts as a DHW
boiler. DHW has Priority.

NO CYCLE The DHW algorithm can steal a boiler that is

already running as a space heating boiler. It does a hot
swap, engaging the DHW pump/valve and leaving the
local pump running or shutting it off. Use this in
conjunction with the LOCAL PUMP OFF: and the
LOCAL DELAY: settings. DHW has Priority.

12. Next is the LOCAL PUMP OFF menu. When a DHW

heating cycle begins, the function of the local
pump/valve is determined:

NO The local pump/valve will remain running during

DHW heating.

YES The local pump will shut off with a delay

determined by LOCAL DELAY: seconds. This
allows the DHW pump/valve to prove before
shutting off the local pump.

Piping of the system will determine which setting to
use.

13. Go to the PURGE TO menu. After a DHW cycle

completes, the pump/valve can be selected to either
purge to the TANK, or to the SPACE for the duration
of the post purge time. This selection can use the space
to dump the heat from the boiler and not overheat the
DHW tank/load.

14. Set the HYB SENSOR = OFF. This sensor is

selectable for Method 5A only.

15. Finally, go to the BOILER MODE menu. If JPS1 has

not been cut, the selection will appear grayed out. Cut
JPS1. Once this is done, set the BOILER MODE to
COMBINATION. The MASTER boiler will control
the temperature in the tank using as many boilers as it
has available on H-Net along with any space heating
needs. The boilers must be piped appropriately for this
method to function correctly.

Now set up the MEMBER boiler(s).
BOILER MODE Set to COMBINATION on

MEMBER boilers, the MASTER is optional,
though it will control MEMBER DHW heating.

DHW SETPOINT This does not need to be set on

MEMBER boilers, only the MASTER boiler.

LOWER BAND This does not need to be set on

MEMBER boilers, only the MASTER boiler.

UPPER BAND This does not need to be set on

MEMBER boilers, only the MASTER boiler.

PUMP PRIORITY This does not need to be set on

MEMBER boilers, only the MASTER boiler.

POST PURGE This needs to be set on all boilers. All

boilers control their respective DHW pump/valve
when they are called to perform DHW heating.

SHARING This can be set on any boiler and will

determine how boilers will cycle on/off when they
are called to perform DHW Heating.

LOCAL PUMP OFF This can be set on any boiler to

determine how the local pump/valve behaves
when called to perform DHW heating.

PURGE TO This does not need to be set on MEMBER

boilers, only the MASTER boiler.

HYB SENSOR: = OFF. This sensor is selectable

for Method 5A only.

JPS1 MUST be cut on all boilers
providing DHW. Cutting JPS1 limits to
maximum temperatures to 200F.

DHW METHODS HeatNet Control V3

Page 40

DHW Method 3: DHW Heating Only, Using a Header Sensor Input

Figure 33 Example: DHW Only Using Header Sensor, Primary/Secondary – Method 3

MASTER

MEMBER 2

MEMBER 3

HNET

HNET

Tank Sensor

Supply H ea der Sensor

Expansion T ank

Cold Water

Makeup

Local Pump

Local Pump

Domestic

Supply

Domestic

Supply

WM

HeatNet

HeatNet

HeatNet

Local Pump

Make

Up

Make

Up

DHW METHOD 3: DHW Heating ONLY using a Header sensor input, Multiple Boilers, Reverse Return.

In this method a Heating Setpoint is maintained at the MASTER’s System Header Sensor located in the DHW tank. The
MASTER’s Heat Demand input enables space heating and maintains the Heating Setpoint at the System Header Sensor. Boilers

are staged to meet the setpoint in the DHW tank based on their runtime, and each boiler will enable its local pump when it is
running. The MASTER modulates the boilers to maintain the Heating Setpoint at the header sensor located in the DHW tank.

DHW METHODS HeatNet Control V3

Page 41

Figure 34 DHW Method 3 Quick Start Settings

DHW METHOD 3: DHW Heating ONLY Using a MASTER and MEMBER boiler(s) Employing H-Net Space Heating PID.

Master

Settings

MASTER Type

HeatNet Address

Combustion Air Damper

Automatic

Automatic

Off

Inputs

Local/Remote

Header Sensor

JPS1 Jumper must be cut to service DHW

Local

Yes - Tank

Outputs

Local Pump On

When Boiler Running

MEMBER 2

Settings

HeatNet Address

Combustion Air Damper

2

Off

Inputs

Local/Remote

JPS1 Jumper must be cut to service DHW

Remote

Outputs

Local Pump/Valve On

When Boiler Running

MEMBER 3

Settings

HeatNet Address

Combustion Air Damper

3

Off

Inputs

Local/Remote

JPS1 Jumper must be cut to service DHW

Remote

Outputs

Local Pump/Valve On

When Boiler Running

DHW METHODS HeatNet Control V3

Page 42

This method will control a tank temperature when the tank
temperature setpoint needs to be maintained for extended
periods with minimal cycling. Multiple boilers can be used
via the H-Net, as this method employs the same PID
algorithm as for space heating. SETTINGS:
DISTRIBUTED CONTROL: MASTER TYPE: AUTO.

1. JPS1 must be cut on all boilers providing DHW

to ensure the maximum output temperature of all
boilers is limited to 200F for DHW operation.

This Method is very similar to the DHW only
method, but:

A. The display will not indicate that it is a

DHW heating boiler.

B. The DHW Heating band will also not be

displayed.

C. The heating band will use the space

heating band and not the UPPER and
LOWER DHW heating band limits.

D. DHW settings are not used.
E. Set the SETTINGS: DISTRIBUTED

CONTROL: MASTER TYPE: to
AUTO.

F. This method is for backwards

compatibility.

2. Use the Heat Demand Control Method 1

located in the CONTROL METHODS section.
Instead of placing the Header sensor in the
Header pipe, place it in a well, in the tank, or a
DHW loop.

The temperature at which boilers are staged ON,
and then OFF is controlled by the SETTINGS:
SETPOINTS: HEAT BAND differential. This
can be understood by referring to the

INTRODUCTION section on the MASTER in
the beginning of this manual.

This differential has the added effect of heating

the tank above the tank’s setpoint temperature. If

the tank setpoint is set to 140F and the heat band
is set to 10F, then the tank temperature will rise
to 145F before the first boiler turns off (setpoint
=140F +/- heat band/2). With (2) boilers running,
the SHED BOILER DELAY time could add to
the tank temperature. So, to ensure that all boilers
are shut off at the upper point of the heat band,
set the SHED BOILER DELAY time to 0 or
other small value. This will effectively turn off
all boilers at the upper heat band point of:
(example) 145F.

Now, there is one more thing to consider, the

pump’s post purge time. Dumping the heat from

all boilers (that were running) using a pump post
purge cycle will have an effect on the tank’s
water temperature. Consider this when

establishing the local pump’s POST PURGE
TIME.

3. Connect to the Local Pump relay contact on J13

to enable the DHW pump. Set its post purge time
to dump the boiler’s heat into the tank when the
boiler shuts off.

4. Enable the system by placing the

LOCAL/REMOTE switch on the MASTER to
the LOCAL position.

JPS1 MUST be cut on all boilers
providing DHW.

DHW METHODS HeatNet Control V3

Page 43

DHW Method 4a: Space Heating with DHW Override of Setpoint on MASTER,
using an Aquastat

Figure 35 Example: DHW METHOD 4a Space Heating with DHW Override of Setpoint on MASTER, using an Aquastat, Primary

Secondary, Reverse Return

DHW METHOD 4a: Space Heating with DHW Override of Setpoint on MASTER, using an Aquastat, Primary
Secondary, Reverse Return

In DHW METHOD 4a, the MASTER’s Heat Demand input enables space heating by energizing the system pump and
maintaining the Heating Setpoint at the MASTER’s System Header Sensor. When the Aquastat located in the DHW tank calls for

heat, the system loop temperature is overridden with the DHW Setpoint. The system pump continues to run, and the DHW pump
is enabled to supply heat to the tanks until the Aquastat is satisfied.

Boilers are staged to meet the active setpoint based on their runtime, and each boiler will enable its local pump when it is running.
The MASTER modulates the boilers in order to maintain the active setpoint.

DHW METHODS HeatNet Control V3

Page 44

Figure 36 DHW Method 4a Quick Start Settings

DHW METHOD 4a: Space Heating with DHW Override of Setpoint on MASTER Using an Aquastat.

MASTER

Settings

Master Type

HeatNet Address

Combustion Air Damper

Auto

Automatic

Off

Inputs

Local/Remote

OR OVR

Header Sensor

System Return

JPS1 Jumper must be cut to

service DHW

Local

Tank Aquastat

Yes

Optional

Outputs

System Pump On

Local Pump On

DHW Pump On

When Boiler Enabled

When Boiler Running

DHW Call

MEMBER 2

Settings

HeatNet Address

Combustion Air Damper

2

Off

Inputs

Local/Remote

JPS1 Jumper must be cut to service DHW

Remote

Outputs

Local Pump On

When Boiler Running

MEMBER 3

Settings

HeatNet Address

Combustion Air Damper

3

Off

Inputs

Local/Remote

JPS1 Jumper must be cut to service DHW

Remote

Outputs

Local Pump On

When Boiler Running

DHW METHODS HeatNet Control V3

Page 45

This method is for controlling DHW utilizing a tank
thermostat connected to a MASTER boiler. This method
requires a thermostat input to the OR OVR. When the
thermostat contact closes across the input OR OVR (J12A
.7 & .8), the control will sense this closure and override the
space heating setpoint with the DHW setpoint. SETTINGS:

DISTRIBUTED CONTROL: MASTER TYPE:
COMBINATION.

This method is for backwards compatibility.

In this mode, the boiler will fire to the DHW setpoint.
The settings for space heating will be used except for
the addition of controlling the DHW pump by the
MASTER boiler.

1. Wire the dry contact from the thermostat on the

tank to the input on J12A terminal 7 & 8 (OR
OVR). Also, at this time wire any pump or valve
from the DHW Pump relay (normally open)
contact (J13 terminals 16, 17, & 18) of the
MASTER to control flow of the heating water
into the tank’s coil.

2. Enter the DOMESTIC HOT WATER MENU.

Go to BOILER MODE and enter AUTO.

3. DHW SETPOINT The setpoint should reflect the

temperature desired in the heating loop when a tank is
calling for DHW heat.

4. LOWER BAND This is not used.

5. UPPER BAND This is not used.

6. PUMP PRIORITY Setting this value to YES will turn

OFF the system pump when the DHW setpoint override
mode is active. Setting this value to NO leaves the

system pump on. This active period includes the post
purge of the DHW/valve pump.

7. Select the menu item POST PURGE. This is the time

that the DHW pump relay remains energized after the
DHW thermostat has been satisfied. Once the tank has
opened its thermostat, the system/local setpoint will be
reloaded and the post purge time will begin.

8. Select the menu item: LOCAL PUMP OFF: When a

DHW heating cycle begins, what to do with the local
pump/valve is determined:

NO The local pump/valve will remain running during

DHW heating.

YES The local pump/valve will shut off with a delay

determined by LOCAL DELAY: seconds. This
allows the DHW pump/valve to prove before
shutting off the local pump.

Piping of the system will determine which setting to
use.

9. Select the menu item: PURGE TO. After a DHW cycle

completes, the pump/valve can be selected to either
purge to the TANK, or to the SPACE for the duration
of the post purge time. This selection can use the space
to dump the heat from the boiler and not overheat the
DHW tank/load.

10. Set the HYB SENSOR = OFF. This sensor is

selectable for Method 5A only.
Follow the same steps as used to program DHW

Heating using a Header Sensor INPUT. USE
SENSOR, select NO.

JPS1 MUST be cut on all boilers
providing DHW.

DHW METHODS HeatNet Control V3

Page 46

DHW Method 4b: Space Heating with DHW Override of Setpoint on MASTER,
using a DHW 10K Tank Sensor

Figure 37 Example: DHW Method 4b: Space Heating with DHW Override of Setpoint on MASTER, using a DHW Sensor,

Primary Secondary, Reverse Return.

MASTER

MEMBER

2

MEMBER

3

HNET

Local Pump

HNET

DHW Pump

DHW Pump

Tank Sensor

Local Pump

Supply Hea der Sensor

System Pum p

Cold Wate r

Makeup

Expansion Tank

Ball Valve

Pressure

Reducing

Backflow

Prevention

System Return Sensor

HeatNet

HeatNet

HeatNet

Domestic

Supply

Cold Wate r

Make Up

Domestic

Supply

Cold Water

Make Up

WM

Water Met er

MIN 3X PIPE DIAMETERS

MAX 10X PIPE DIAME TERS

BETWEEN CENTERS (TYP)

System Return

Sensor

System Heade r Sensor

Local Pump

System

Pump

System

Supply

System

Return

DHW METHOD 4b: Space Heating with DHW Override of Setpoint on MASTER, using a DHW Sensor, Primary
Secondary, Reverse Return

In DHW METHOD 4b, the MASTER’s Heat Demand input enables space heating by energizing the system pump and
maintaining the Heating Setpoint at the MASTER’s System Header Sensor. The MASTER’s OR OVR input is jumped to enable

DHW heating using the DHW tank sensor. When the DHW tank temperature drops, a DHW heat demand is generated, and the
system loop temperature is overridden with the DHW Setpoint. They system pump continues to run, and the DHW pump is
enabled to supply heat to the tanks until the DHW tank is satisfied.

Boilers are staged to meet the active setpoint based on their runtime, and each boiler will enable its local pump when it is running.
The MASTER modulates the boilers in order to maintain the active setpoint.

DHW METHODS HeatNet Control V3

Page 47

Figure 38 DHW Method 4b Quick Start Settings

DHW METHOD 4b: Space Heating with DHW Override of Setpoint on the MASTER Using a 10K Tank Sensor.

Master

Settings

MASTER Type

HeatNet Address

DHW Use Sensor

Combustion Air Damper

Auto

Automatic

Yes

Off

Inputs

Local/Remote

OR OVR

Header Sensor

System Return

DHW Sensor

JPS1 Jumper must be cut

Local

Jumper

Yes

Optional

Yes - Tank

to service DHW

Outputs

System Pump On

Local Pump/Valve On

DHW Pump On

When Boiler Enabled

When Boiler Running

DHW Call

MEMBER 2

Settings

HeatNet Address

Combustion Air Damper

2

Off

Inputs

Local/Remote

JPS1 Jumper must be cut to service DHW

Remote

Outputs

Local Pump On

When Boiler Running

MEMBER 3

Settings

HeatNet Address

Combustion Air Damper

3

Off

Inputs

Local/Remote

JPS1 Jumper must be cut to service DHW

Remote

Outputs

Local Pump On

When Boiler Running

DHW METHODS HeatNet Control V3

Page 48

This method is for controlling DHW utilizing a 10k sensor
in the tank connected to DHW TANK (J10A, 9 & 10) of a
MASTER boiler. This method is only available on the
MASTER boiler since its purpose is to override the setpoint.
This method requires a jumper input to the OR OVR (J12A
7 & 8), which acts like an enable. The control will sense this
closure and override the space heating setpoint with the
DHW setpoint when the DHW tank temperature drops
below the lower band of the DHW setpoint. All boilers are

started and stopped using the space heating “Modular

Boiler” settings. SETTINGS: DISTRIBUTED

CONTROL: MASTER TYPE: COMBINATION.

In this mode, the boiler will fire to the DHW setpoint.
The settings for space heating will be used except for
the addition of the MASTER Boiler controlling the
DHW pump/valve.

1. Wire the 10K Tank sensor to the MASTER on

DHW TANK (J10A, 9 & 10). Jumper the input
on J12A terminal 7 & 8 (OR OVR). Also, at
this time wire any pump or valve from the DHW
Pump relay contact (J13 terminals 16, 17, & 18)
N/C, C, & N/O respectfully to control flow of
the heating water into the tank’s coil.

2. Enter the DOMESTIC HOT WATER MENU.

Go to BOILER MODE and enter AUTO.

3. DHW SETPOINT The setpoint should reflect the

temperature desired in the heating loop when a tank is
calling for DHW heat.

4. LOWER BAND This is not used.

5. UPPER BAND This is not used.

6. PUMP PRIORITY Setting this value to YES will turn

OFF the system pump when the DHW setpoint override

mode is active. Setting this value to NO leaves the
system pump on. This active period includes the post
purge of the DHW pump/valve.

7. Select the menu item POST PURGE. This is the time

that the DHW pump relay remains energized after the
DHW demand has been satisfied. Once the tank has
reached temperature, the system/local setpoint will be
reloaded and the post purge time will begin.

8. Select the menu item: LOCAL PUMP OFF: When a

DHW heating cycle begins, what to do with the local
pump/valve is determined:

NO The local pump/valve will remain running during

DHW heating.

YES The local pump will shut off with a delay

determined by LOCAL DELAY: seconds. This
allows the DHW pump/valve to prove before
shutting off the local pump.

Piping of the system will determine which setting to
use.

9. Select the menu item: PURGE TO. After a DHW cycle

completes, the pump/valve can be selected to either
purge to the TANK, or to the SPACE for the duration
of the post purge time. This selection can use the space
to dump the heat from the boiler and not overheat the
DHW tank/load.

10. Set the HYB SENSOR = OFF. This sensor is

selectable for Method 5A only.

Follow the same steps as used to program DHW Heating
using a Header Sensor INPUT. USE SENSOR, select Yes.

JPS1 MUST be cut on all boilers
providing DHW.

DHW METHODS HeatNet Control V3

Page 49

DHW Method 5a: Local DHW Tank Heating using a 10k Tank Sensor.

Figure 39 Example: DHW Heating to a Local Boiler’s Tank,– Method 5a

MASTER

MEMBER

2

MEMBER

3

HNET

Local Pu mp

Local Pu mp

HNET

DHW Pum p

DHW Pum p

System Return

Sensor

Domestic Hot

Water

Domestic Hot

Water

Tank Sensor

Supply H eader Se nsor

Local Pu mp

System Pump

System Re turn Sen sor

Expansion T ank

Cold Wate r

Makeup

HeatNet

HeatNet

Supply

Make Up

Supply

Make Up

WM

Tank Sensor

DHW S ensor

DHW S ensor

HeatNet

System Pum p

System

Supply

System

Return

DHW METHOD 5a: Local DHW Tank Heating Override using a 10K Type II Tank Sensor.

In DHW METHOD 5a: Local DHW Tank Heating Override, the MASTER’s Heat Demand input enables space heating by
energizing the system pump and maintaining the Heating Setpoint at the MASTER’s System Header Sensor using the available
MEMBERs. A MEMBER boiler will enable its local pump when called to service a heating call by the MASTER. Each
MEMBER has its OR OVR input jumped to enable local DHW heating using its DHW Sensor. When a DHW tank sensor calls for
heat, the local boiler goes offline from the MASTER. The boiler can disable its local pump (Programmable), and enables its
DHW pump/valve to service the local tank until the tank sensor has been satisfied. Once the call for DHW heat has been satisfied,
the boiler is placed back online for the MASTER to service the main heating loop.

DHW METHODS HeatNet Control V3

Page 50

Figure 40 DHW Method 5a Quick Start Settings

DHW METHOD 5a: Local Tank Heating Using a DHW Tank Sensor

MASTER

Settings

MASTER Type

HeatNet Address

Combustion Air Damper

Automatic

Automatic

Off

Inputs

Local/Remote

Header Sensor

System Return

Local

Yes

Optional

Outputs

System Pump On

Local Pump On

When Boiler Enabled

When Boiler Running

MEMBER 2

Settings

HeatNet Address

DHW Boiler Mode

DHW Use Sensor

DHW Local Pump Off

Combustion Air Damper

2

Local

Yes

Yes

Off

Inputs

Local/Remote

OR OVR

DHW Sensor

JPS1 Jumper must be cut to service DHW

Remote

Jumper

Yes - Tank #1

Outputs

Local Pump On

DHW Pump On

Space Heating Call

DHW Call

MEMBER 3

Settings

HeatNet Address

DHW Boiler Mode

DHW Use Sensor

DHW Local Pump Off

Combustion Air Damper

3

Local

Yes

Yes

Off

Inputs

Local/Remote

OR OVR

DHW Sensor

JPS1 Jumper must be cut to service DHW

Remote

Jumper

Yes - Tank #2

Outputs

Local Pump On

DHW Pump On

Space Heating Call

DHW Call

DHW METHODS HeatNet Control V3

Page 51

This method is used to provide combination space heating
and DHW heating. The boiler may be standalone or in a
HeatNet configuration. It is meant to fire an individual

boiler in a DHW heating Priority mode when that boiler’s

local tank temperature has a call for DHW heat (tank

sensor’s temperature drops below the DHW Setpoint +

LOWER BAND). The boiler will stop space heating (if
running) and switch to DHW heating. The DHW
pump/valve will be engaged and the water temperature in
the tank will be maintained by the boiler at the DHW
setpoint. Once the tank temperature exceeds the Setpoint +
UPPER BAND temperature, DHW heating will stop and the

pump/valve’s post purge will start.

When a tank’s temperature sensor is connected directly to a

boiler and the BOILER MODE is set to LOCAL. The
boiler will go offline from HeatNet and service the DHW
needs of its local tank. If the boiler is running in space

heating mode, then the “SHARING” setting may be used to

determine how, or if, to shut down before starting a DHW
cycle. When the DHW cycle is complete (includes the post
purge time of the DHW pump), the boiler will go back
online with HeatNet and become available to fire.

During a DHW cycle the DHW setpoint will be loaded
along with the UPPER and LOWER BAND limits. Also,
the SETTINGS: DISTRIBUTED CONTROL: MASTER
TYPE: is set to AUTO.

When a 10k Type II sensor is used with this method, the OR
OVR input functions as an enable/disable. This allows the
DHW heating function to be enabled or disabled much in
the same way as the Heat Demand input for space heating.

When using this method, a DHW band is also available in
the Home Screen. The space heating band will be displayed
on the left and the DHW Heating band on the right. The
bands will operate in a split screen view.

1. Connect a 10k thermistor from the DHW tank’s sensor

well to J10B terminals on any boiler. Wire a pump or
valve from the DHW pump or the System pump
(normally open) relay contact to control flow of the
heating water into the tank’s coil or system loop.

The System pump will always be enabled by the
MASTER as long as the Heat Demand input is closed
(In this example the Master is not a DHW boiler). The
DHW pump/valve will be enabled on the LOCAL
DHW MEMBER whenever there is a DHW call for
heat.

A DHW call for heat is when the DHW temperature is
below the (DHW SETPOINT – LOWER BAND) or
when the DHW temperature is below the (DHW
SETPOINT + UPPER BAND) and boilers are firing.
After a DHW call for heat ends:

A. The pump/valve will remain enabled during a

post purge pump cycle until the post purge timer
expires.

2. Next, enter the DOMESTIC HOT WATER menu on

the MEMBER boiler. Go to BOILER MODE and
enter LOCAL.

3. Change the DHW SETPOINT to the desired target

temperature of the water in the tank. Once the control
determines there is a call for DHW, the DHW
SETPOINT is loaded and the boiler will target the
setpoint.

4. Now, change the LOWER BAND to the desired

temperature (DHW SETPOINT – LOWER DHW
DIFF) below which boilers are to be added. This setting
corresponds to the minimum water temperature
required in the tank. DHW heating will be initiated
when the DHW tank’s water temperature is below the
temperature (DHW SETPOINT – LOWER BAND).

How long the temperature of the tank stays below the
temperature (DHW SETPOINT – LOWER BAND) is
used to determine when boilers are started along with
the ADD BOILER DELAY TIME.

5. Next, change the UPPER BAND to the desired

temperature (DHW SETPOINT + UPPER BAND)
above which boilers are to be shed. This setting is the
maximum tank temperature. Setting the SHED
BOILER DELAY TIME correctly will limit the
maximum tank temperature to the (DHW SETPOINT +
UPPER BAND). Setting the SHED BOILER DELAY
TIME = 0 will shut off all boilers immediately once the
(DHW SETPOINT + UPPER BAND) is exceeded.

6. Change the DHW PRIORITY. Setting this value

to YES will turn OFF its system pump when the
DHW mode is active (when the DHW pump is
on). Setting this value to NO leaves the system
pump on.

7. Now got to the POST PURGE menu. This is the

time that the DHW pump relay remains energized
after the DHW SETPOINT has been satisfied.

A. The pump/valve will remain on during a

post purge pump cycle until the post purge
timer expires.

8. Now, go to the USE SENSOR menu and select

YES. This will allow the boiler to control the
local tank or DHW loop temperature using the
DHW sensor. The upper and lower differential
temperatures will also be loaded.

9. Got to SHARING and set it to OFF or CYLE if

the boiler is currently running in space heating
and needs to be shut down before starting up in
DHW.

DHW METHODS HeatNet Control V3

Page 52

If SHARING is set to NO CYCLE, a hot swap
will occur. A hot swap is when the boiler is
running in space heating mode and does not need
to be shut down. The DHW pump/valve will be
energized without the boiler stopping. Once the
DHW cycle has completed, the boiler will stop
and wait to be called again for either space
heating or DHW heating. A shutdown always
occurs after a DHW cycle completes.

10. Set the LOCAL PUMP/VALVE OFF to NO.

This will leave the local pump on during a DHW
heating cycle (backwards compatibility).

Setting this value to YES, will shut the local
pump off during a DHW heating cycle, but will
keep the local pump on for the LOCAL
DELAY: 10s (Programmable) time before
shutting off.

11. Set the PURGE TO value to TANK. This will

purge the heat from the boiler into the tank or
system loop. This will be done using the DHW
pump after the DHW heating cycle is complete.

If the PURGE TO: is set to SPACE, once the DHW
cycle has completed, the boiler will shut the DHW
pump off within a few seconds. The SPACE setting is
to be used only for MIXED space and DHW heating.

HYB SENSOR = OFF
SETTINGS: DISTRIBUTED CONTROL:

MASTER TYPE select AUTO,
DHW or COMBINATION.

JPS1 MUST be cut on all boilers
providing DHW.

DHW METHODS HeatNet Control V3

Page 53

DHW Method 5b: Local DHW Tank Heating using a Thermostat & Hybrid
Sensor.

Figure 41 Example: DHW Heating to a Local Boiler’s Tank, Movable Sensor Location – Method 5b

System Heade r Sensor

MASTER

MEMBER

2

MEMBER

3

HNET

Local Pump

HNET

DHW Pump

DHW Pump

System Re turn

Sensor

DHW Sensor

OR OVR

Supply

Sensor

OR OVR

Supply Hea der Sensor

System Pum p

HeatNet

HeatNet

Domestic

Supply

Cold Wate r

Make Up

Local Pump

Cold Wate r

Makeup

Expansion T ank

Domestic

Supply

Cold Wate r

Make Up

WM

Optional

Location

Optional

Location

Return Heade r Sensor

HeatNet

System Pum p

Tank Thermos tat

Tank Thermos tat

System

Supply

System

Return

DHW METHOD 5b: Local DHW Tank Heating using an aquastat and a Hybrid Sensor.

In DHW METHOD 5b: Local DHW Tank Heating using an aquastat and a Hybrid Sensor, the MASTER’s Heat Demand input

enables space heating by energizing the system pump and maintaining the Heating Setpoint at the MASTER’s System Header

Sensor using the available MEMBERs. A MEMBER boiler will enable its local pump when called to service a heating call by the
MASTER.

Each MEMBER has its OR OVR input connected to a local tank aquastat. This method allows the DHW Temperature Sensor to
be placed in many locations. This sensor is called the Hybrid Sensor. When the aquastat located in the DHW tank calls for heat,
the local boiler goes offline from the MASTER and services the DHW call. The MEMBER then disables its local pump/valve,
and enables its DHW pump to maintain the DHW Setpoint at the Hybrid Sensor location. Once the DHW aquastat has been
satisfied, the boiler is placed back online for the MASTER to service the main heating loop.

MEMBER 2 is configured to use its Local Supply sensor when servicing DHW demands, and MEMBER 3 is configured to use its
DHW sensor.

DHW METHODS HeatNet Control V3

Page 54

Figure 42 DHW Method 5b Quick Start Settings

DHW METHOD 5b: Local Tank Heating using a Hybrid Sensor (DHW, Supply, or Return)

MASTER

Settings

MASTER Type

HeatNet Address

Combustion Air Damper

Automatic

Automatic

Off

Inputs

Local/Remote

Header Sensor

System Return

Local

Yes

Optional

Outputs

System Pump On

Local Pump On

When Boiler Enabled

When Boiler Running

MEMBER 2

Settings

HeatNet Address

DHW Boiler Mode

Combustion Air Damper

2

Local

Off

DHW Use Sensor

Hybrid Sensor

DHW Local Pump Off

No

Supply

Yes

Inputs

Local/Remote

OR OVR

JPS1 Jumper must be cut to service DHW

Remote

Tank Aquastat

Outputs

Local Pump On

DHW Pump On

Space Heating Call

DHW Call

MEMBER 3

Settings

HeatNet Address

DHW Boiler Mode

Combustion Air Damper

3

Local

Off

DHW Use Sensor

Hybrid Sensor

DHW Local Pump Off

No

DHW

Yes

Inputs

Local/Remote

OR OVR

JPS1 Jumper must be cut to service DHW

Remote

Tank Aquastat

Outputs

Local Pump On

DHW Pump On

Space Heating Call

DHW Call

DHW METHODS HeatNet Control V3

Page 55

Method 5b can also be used in a Hybrid mode on
MEMBER boilers with a thermostat connected to the OR
OVR input. This will enable DHW heating, and be used

instead of having the 10k sensor’s temperature detect

when DHW heating is needed, but will use a selectable
sensor instead to maintain setpoint.

When the OR OVR input sees the thermostat close, the DHW
pump/valve will be engaged and remain energized as long as
the OR OVR input sees that the thermostat is closed. The
DHW setpoint along with the DHW heating band will then
be loaded. A steady temperature will now be maintained
using the HYB SENSOR setting in the DHW menu. This

sensor will control the water temperature at the sensor’s

location, enabling or disabling the boiler as needed until the
OR OVR input sees the thermostat open. Once the
thermostat opens, the DHW pump post purge will begin.

The difference between the settings of method 5a vs. method

5b is the “USE SENSOR” setting. 5a requires that the “USE
SENSOR” setting be set to YES, and the 5b “USE
SENSOR” setting be set to NO. The HYBRID SENSOR

setting must also be set in the 5b mode to the sensor where
temperature needs to be maintained. It must be set to OFF in
the 5a method.

Method 5a USE SENSOR = YES

HYB SENSOR = OFF

Method 5b USE SENSOR = NO

HYB SENSOR = SUPPLY, DHW,

RETURN

Each sensor selection/location has its advantages. Select the:

Supply sensor will limit the temperature/firing rate of the
boiler, but may not be sufficient for continuous demand or
speed in heating the tank. It is already available, so no
additional sensor is needed.

Return sensor will allow the boiler to run its supply
temperature up quickly, but may bounce off of the operating
limit band. This would heat the tank in the shortest time, but
may overheat the tank. It is already available, so no
additional sensor is needed.

DHW sensor will allow the placement anywhere needed to
maintain that locations temperature. This is an additional
sensor that needs to be acquired.

A thermostat can be placed in a tank and connected to the OR
OVR input. (On MEMBER boilers only, The MASTER
uses OR OVR already with DHW METHOD 4), When the
thermostat contact closes across the input OR OVR (J12A .7
& .8) on a MEMBER boiler, the control will sense this
closure and disconnect itself from HeatNet. It will perform

the DHW call, post-purge the pump, and put itself back on
line available for space heating.

DHW METHOD 6: DHW using Direct
Control (Not preferred)

If the control’s SETTINGS: 4-20 mA input is set to
PRIORITY = HIGH the 4-20 mA signal, once brought above
the 4-20 mA starting current, can be used to override any
other Heat Demand and direct modulate the boiler.

This can be set in menu: ADVANCED SETUP: 4-20 mA
INPUT. It allows a MEMBER boiler to be taken offline and
directly modulated by an external control.

If the MASTER is using it for heating and the ADVANCED
SETUP: 4-20 mA is set to PRIORITY= HIGH, an external
control can now output a 4-20 mA signal which will take
over the boiler’s fire rate and override all other heating
demand inputs. The external control would also need to open
any valves or turn on pumps. This is typically used for DHW
Control.

Using the 4-20mA input (OPTIONAL)

The 4-20mA input is designed to operate per the ISA-50.1
standard. It will support Type 2, Type 3, and Type 4
Transmitter/Receiver circuits.

With the type 4 configuration, multiple boilers (up to 5), may
be connected in series using the –mA +mA –mA +mA
scheme (no jumper to 24VDC RET). This allows one 4­20mA transmitter to control multiple boilers. A free-floating
250 ohm resistor is viewed by the BMS (or external
control’s) 4-20mA transmitter across the + and –4-20mA
terminals with this method. The 4-20mA (1) input is used to
control direct modulation and for remote setpoint control.

The Type 2 and Type 3 circuit may use the supplied
+24VDC and 24VDC RET connections (J10B) to power a
remote transmitter. The –mA terminal will need to have a
jumper connected to the adjacent 24VDC RET terminal to
reference the signal ground.

The 4-20mA (2) input is reserved for flow meters and
ancillary devices.

OPTIONAL FEATURES HeatNet Control V3

Page 56

Figure 43 Example: 4–20 mA connections

Channel 1:

4-20mA/0-10VDC

(+)

(-)

Channel 2:

4-20mA/0-10VDC

(+)

(-)

24 VDC Return

24 VDC

Figure 44 4–20 mA enable connection

Closing this contact enables
the 4-20mA/0-10VDC input

The 4-20 mA input uses a 250 ohm sense resistor to convert
the current to a voltage from 1 to 5 volts DC for the control
to use. For this reason, a 1-5 VDC control voltage may also
be used across the 4-20mA +/- input, but it still needs to
supply the necessary current, i.e. 20mA. This resistor is
located on the bottom side of the control board. When a 4.02
mA signal is sensed, the boiler will initiate a start sequence
and fire the boiler at its minimum setting if the REMOTE
ENABLE input is closed. This is typically 25% of the boilers
output (4:1 turndown).

If the dip switch S6 is set to the 0-10 position (UP) See:
Figure 49, the 4-20mA input will accept a 0-10 VDC signal.
The channel will also need to be setup in the menu:

ADVANCED SETUP: 4-20mA INPUT: CHANNEL
MODE. The operating range will be from 2-10 VDC or

twice what was previously stated for the 1-5 VDC

functionality. To convert a 0-10VDC signal to mA, divide
by 2510 (ohms).

NOTE: Due to the inability of control voltage methods (1-5,
2-10 VDC) to reject noise and compensate for line loss, the
use of the 4-20mA control current is recommended. The
control voltage methods may be less expensive, but are the
least stable. If using a 0-10VDC control signal, a source
current of a minimum 5mA is required.

If using a remote panel with a relay and a 4-20 mA
transmitter for operation, connect the 4-20mA transmitter
output from the remote panel to the Member boilers using the
floating 250 ohm method (type 4). The relay contacts on the
remote panel will then be connected to the associated 4­20mA REMOTE ENABLE inputs on the associated boiler(s).

The minimum setting of the boiler is calibrated

so that the minimum PWM signal to control
the Blower motor is 20%. The VFD to blower
motor operates with a control signal from 20%

- 80% Pulse Width Modulation. This PWM
signal to the VFD can be measured using a
multimeter. It is a 0–10volt square wave signal
at 110 Hertz. A 20% modulation signal will
read 2.0 VDC, and an 80% modulation signal
will read 8.0 VDC on an RMS multimeter. See
Figure 59, page 75.

For direct fire applications, the 0-10 volt
control signal is proportional to the output.
Such that: 1 volt will track linearly by 10%.
So, 1v=10%, 2v=20%, 3v=30%,
4v=40%... The control signal will still be
limited by the turndown and the 4-20mA
INPUT menu.

Setpoint Control functionality can be implemented remotely
using the 4-20mA input. This function translates a 4 to 20mA
control signal to a setpoint mapped from 50F to 220F. The
feature is enabled in the SETPOINTS menu as: SETUP:

SETPOINTS: SETPT SOURCE 4-20mA.

ADVANCED SETUP: 4-20mA INPUT: CHANNEL
MODE. Also, when selecting; SETUP: SETPOINTS:

SETPT SOURCE and selecting 4-20mA, the 4-20mA INPUT
menu will be automatically entered.

You may now select the current at which the boiler will start.
It is adjustable from 3.7mA to 5mA. Hysteresis of .1mA is
always in effect. So, if the starting mA = 4.10mA the boiler
will start when the control current applied achieves this value
of 4.10mA. The boiler must drop .1mA below this to turn
OFF, in this example 4.00mA. This hysteresis value is not
adjustable.

When using the 4-20mA setpoint control, a band may now be
set at which the 4-20mA signal will operate over. The lower

OPTIONAL FEATURES HeatNet Control V3

Page 57

setpoint is defined as 4mA SETPOINT and the upper setpoint
is defined as 20mA SETPOINT. The 4mA SETPOINT is
linked to the BOILER START x.xxmA where this starting
current is the lower setpoint. So, if we set the 4mA
SETPOINT to 130F and the 20mA SETPOINT at 180F we
will have established the band. Once a starting control
current of BOILER START 4.1mA is applied, and the 4-20
REMOTE ENABLE INPUT is closed, the boiler will start
and the setpoint will be set to 130F. If a control current of
10mA is applied the boiler will track on a linear slope
towards the 20mA SETPOINT settling at a SETPOINT of
~149F. As the current increases to 20mA, the SETPOINT
will indicate 180F. The Default setting is 4mA SETPOINT:
50F, and 20mA SETPOINT 220F for backwards
compatibility with the older version. NOTE: anytime a new
firmware version is uploaded to the control, these values
return these defaults.

Anytime a new firmware version is uploaded

to the control, these values return to these
defaults.

If using the direct modulation mode by applying a 4-20mA
current, only the BOILER START x.xxmA setting applies.

The 4-20 mA input can be set to HIGH PRIORITY. This is
done in menu: ADVANCED SETUP: 4-20mA INPUT:
CHANNEL MODE. This allows a Member boiler to be
taken offline and directly modulated by an external control. If
the Master is using it for heating and the 4-20mA is set to
HIGH PRIORITY, an external control can now output a 4-

20mA signal which will take over the boiler’s fire rate. This

is typically used for DHW control.

Setpoint Priorities

Changing the setpoint can be done in many ways. If a higher
level setpoint control is lost, the next level setpoint control is
used until the System Setpoint is loaded. The setpoints are
prioritized in the following order:

1. 0-10V, 4-20MA setpoint Control

2. BMS, Modbus Setpoint

3. Outdoor Reset Setpoint

4. Menu’s System Setpoint

Any Setbacks that are active are then applied.

Circulator Pump Options

There are provisions for 2 system pumps (1 system pump if
Lite version) and a local pump. This is to allow for
primary/secondary loop configurations. The system circulator
pump is implemented using the K4, K13 RELAY and

normally open contacts at J16 SYSTEM PUMP 1 and
SYSTEM PUMP 2.

The pumps require motor contactors to isolate

the on-board relay contacts. The on-board
relays should never be used to energize large
pumps directly. Figure 45 illustrates the
connections without contactors for illustrative
purpose.

Figure 45 System Pump connections

The system circulator pump is supported by (2) modes and
special features.

1. The first mode will allow the circulator pump to remain

on, unless the control’s outside high air temperature

setting has been met when using OUTDOOR AIR
RESET.

2. The second mode will allow the circulator pump to be

turned on whenever there is a call for heat (any control
input). This mode will stop the circulator pump when the
call for heat is lost and the pump post purge time has
been satisfied.

The summer pump jog is a special feature that can be
selected when the system is in summer shutdown
(OUTDOOR RESET). The jog allows the system circulator
pump(s) and the local pump to run for the system pump
purge time once a week. It can be set to any day of the week
and will occur at 12:01 AM. If (2) system pumps are present,
and after the first pump finishes its post purge, the second
one will start and the first one will stop.

K4

K13

System Flow
Prove Switch

System Pump 1

System Pump 2

(Not Available

On Lite Version)

OPTIONAL FEATURES HeatNet Control V3

Page 58

The system flow proving switch is implemented using
SPARE 3/System Water Flow on J11A. If a flow switch is
connected to the WTR FLW interlock, the HeatNet control
will wait up to 10 seconds to prove flow. If flow is
interrupted after it has been established, an error will be
displayed and the boiler will cycle OFF. As long as there is a
call for heat, every 10 minutes the circulator pump will try to
re-establish flow and start the boiler again.

When (2) system pumps are present and flow is not
established or is lost (2) things will occur to try and keep heat
in the system.

1. When first starting a system: If after a 10 second

wait to establish flow has failed, the first pump will
change to the second pump. The second pump will
now try to establish flow for 10 more seconds. If the
second pump fails to establish flow, the HeatNet
control waits 10 minutes. After the 10 minutes has
expired, the control now starts with the second pump
and attempts to prove flow for 10 more seconds. If
flow does not prove, the control changes to the first
pump and attempts to prove flow. This cycle will
continue indefinitely until flow is established. If flow
is lost while running: this process is also used in an
attempt to re-establish flow.

2. If PUMP ROTATION is set to PMP HRS the PUMP

ROTATION will be temporarily set to SYS HRS. This
is to prevent re-starting the failed pump due to its
runtime hours. Setting the PUMP ROTATION to SYS
HRS will allow a retry of the failed pump after the
rotation hours has expired. Power cycling of the boiler
or using the PUMP ROTATION menu will revert
back to PUMP ROTATION = PMP HRS if this was
the original setting.

For system pump modulation a 0-10Vdc control signal
output is provided at J4.3 (signal) and J4.7 (ground). This
signal is output by the Master boiler as a percent function of
the number of boilers running and can be used to set the
speed of a System Pump using a Variable Frequency Drive.
Two wires are required and need to be inserted into the J4.3
and J4.7 positions to access this signal.

This signal has a step response and is not linear
to the system or boiler’s input firing rate.

The output signal is proportionally mapped to % using the
equation:

%VFD = (boilers running/total boilers)
The %VFD represents the stepped percentage of boilers

running where:
0Vdc = 0% (to) 10Vdc = 100%
If there are (6) boilers in a system and (2) are running, the

control signal = 33% or 3.3Vdc. This signal could then be
applied to a system pump’s VFD to control the speed of the

pump relative to how many boilers are firing. The VFD
would need to be set appropriately to allow the correct flow
through each boiler.

In low volume systems sudden temperature changes may
occur when the flow is stepped up or down by a large
percentage. In these situations the ADAPTIVE MOD may
need to be disabled and the ORIGINAL KN method used.
Other adjustments may also be required.

Currently, no failsafe mode is available in the event the
Master boiler’s control fails. If this method is employed, a
failsafe boiler could be used to override the control signal

and enable the system pump’s VFD using some external

wiring and an external relay, or have the VFD default to a
safe speed on loss of the control signal.

If (2) pumps are available (Full, not Lite version), pump
rotation is available. The rotation of the (2) pumps can be
controlled using two methods.

3. Pumps are switched based on the system run time

4. Pumps are switched by the difference between each

pump’s runtime. The HeatNet control keeps a

running record of each pump’s runtime in hours. If

a pump is taken offline or replaced. The runtimes
can then be adjusted until they become equal.

These features may be selected in the menu, SETUP: PUMP
OPTIONS: SYSTEM PUMP: PUMP ROTATION

The local circulator pump is supported by (3) modes and
(2) features.

1. The first mode allows the circulator pump to remain on,

unless the control’s outside high air temperature setting

has been met when using Warm Weather Shutdown.

2. The second mode will allow the circulator pump to be

turned on whenever there is a call for heat (any control
input). This mode will stop the circulator pump when the
call for heat is lost and the pump post purge time has
been satisfied.

3. The third mode works much the same as mode 2, but it

allows the inlet sensor (RETURN) to be used with the
outlet sensor (SUPPLY) to keep the pump on until a
delta (difference) temperature is met. A return
temperature sensor is required for this mode, because the
delta temperature (SUPPLY – RETURN) measured is
across the boiler. In this mode, the post purge time is
also used. After the delta temp has been met, the post
purge time needs to expire before the pump is turned off.
This mode works much the same as mode 2.

OPTIONAL FEATURES HeatNet Control V3

Page 59

Local Pump Option

LOCAL PUMP/VALVE OPTION: This is a special
feature, when using valves, it prevents deadheading water
flow when all boilers are off. When this feature is enabled,
the Master boiler will enable its local valve when NO boilers
are running. If boilers are running in LOCAL override and
not controlled by H-NET, but are visible to H-NET, the
valve(s) on these boilers are presumed OPEN. In this
situation, the Master will not enable its valve unless it is
running.

Figure 46 Local & DHW Pump connections

Local Pump/Valve

Normally Closed &

Normally Open Contacts

DHW

Normally Closed &

Normally Open Contacts

Another feature of the PUMP/VALVE OPTION is to control
a local (primary) pump using a Variable Frequency Drive.
This feature may be required when a secondary system pump
is also variable speed. To enable this feature: SETUP:

PUMP OPTIONS: LOCAL PUMP PUMP/VALVE
OPTION: LOCAL PUMP VFD: ON. Setting this Option to

ON will map the control signal on J4 pins 1+ and 5- to the
modulation rate. 2 wires need to be run from J4.1+ and J4.5­to the VFD’s input connection. Ensure that the JS1 shunt
jumper on the control board is in position 0-10 or 4-20mA as
required.

Auxiliary Function Options

Combustion Air Damper

Relay K5 and the terminal J13 DAMPER is used to control a
combustion air damper. J12B.7 & .8 are used to detect the
dry contact proof switch from the damper. J12B.7 is the
sense input and J12B.8 is 24VAC. A proof time of up to 4
minutes can be set before the boiler can start or an alarm
condition will occur. The Combustion Damper can be setup
in the SETUP: AUX FUNCTIONS menu.

Using the LINKED/COMMON setting, the Master boiler
controls a system damper, so in the event this damper fails to

open, the system will not start. If the Master boiler’s system

damper fails, then no call for heat will be made to the
Member boiler(s).

Using the INDEPENDENT setting, each Member boiler can
control its own damper and is independent of the Master
boiler when a call for heat is made to the Member. This
allows for separate dampers for each boiler. They can be
wired to J12B terminals 7 and 8.

If a common system damper is used (controlled by the
Master boiler), each individual boiler must prove that the
combustion air damper is open when it is placed in LOCAL.
This may be done using J12B terminal 7 on all boilers wired
to the damper’s prove switch. Terminal 7 is the sense input
and terminal 8 is 24 VAC. Connecting a wire to terminal 8 is
not recommended.

See Figure 60, Common system damper wiring, Page 76.

A separate/independent 24 VAC source is

recommended to be used for the damper prove
switch when a common system damper is
used. If you use terminal 8 to supply power
from the Master and the Master is powered
OFF, no boiler will be allowed to fire due to
the loss of power through the prove switch. A
backup boiler will also need to have the
damper relay contacts wired in parallel with
the Master for when the Master is powered
OFF.

A second wire on the Master J12B terminal 7 is then
connected. The other end of this wire is then run to the first
Member boiler J12B terminal 7. If another Member boiler is
present, a second wire can be connected to the first Member
boiler J12B terminal 7 and the other end connected to the
other boiler J12 terminal 7. This method can be continued if
additional boilers are present. This input must be selected in
the SETUP: AUX FUNCTIONS: COMBUST AIR
DAMPER menu.

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Page 60

Outdoor Reset

The Outdoor reset feature allows the water setpoint
temperature to change dynamically with the outside air
temperature. It also provides an adjustable temperature that
shuts the boiler (or boiler system) down when the outside
temperature rises above it.

WATER TEMP

LOW OA TEMP

180 °F

10 °F

Water temp @
outside air temp

WATER TEMP

HIGH OA TEMP

140 °F

70 °F

Water temp @
outside air temp

WWS Setpoint

72 °F

Outside air temperature
where Warm Weather
Shutdown occurs

WARM WEATHER SD=ON

If set to ON here

Figure 47 Outdoor reset curve, typical

The above chart shows how the water temperature setpoint
changes with the Outside air temperature. The four values of
180, 10 and 140, 70 are the default values:

The chart depicts what the water temperature setpoint will
equal with a corresponding outside air temperature. At an
outside temperature of 10F and below, the water temperature
setpoint will be limited to 180F. With an outdoor temperature
of 70F and above, the water temperature will be limited to
140F. The water temperature setpoint will track along the
charts plotted line with corresponding outside temperatures.

The OR OVR (Outdoor Reset Override) input on J12A can
be used to override this Outside Air Setpoint and maintain
the water setpoint at the LOCAL or SYSTEM SETPOINT

value when a contact is closed across this input. This can be
used as a Domestic Hot Water demand input.

Another function of the OUTDOOR RESET is the
Winter/Summer mode ((W)arm (W)eather (S)hutdown).
With the WWS SETPOINT set to 72F and WARM
WEATHER SD set to ON, the boiler/system will enter
summer shutdown when the Outside Air temperature rises
above 72F. While in this state, the OR OVR input on J12A
can be used to bring the boiler/system on to maintain the
water setpoint at the LOCAL or SYSTEM SETPOINT value.

During WWS operation, the System pump will not be
enabled just the Local pump unless the SETUP: SYSTEM
PUMP: OVR ENAB IN WWS is set to ON. This is the
System Pump Priority mode. When SETUP: SYSTEM
PUMP: OVR ENAB IN WWS is set to OFF, the system
pump will not come on while in WWS with the OR OVR
override input closed.

Sensors

The H-Net control supports a standard 10K thermistor (Type
ACI/10K-CP). These sensors can be calibrated to the control
by entering the sensor menu and placing a precision 10k
resistor on an input.

Sensors should be wired using a twisted

shielded pair cable of 18-22 AWG wire.

Immersion sensors must have wells.

Stack Temperature

If the boiler is a Fusion PVC model, the Stack sensor is
preconfigured and will only operate with a working 10k stack
sensor and HeatNet Firmware designated as PVC. Switch
S5.3 should be set to the 10K STACK position and S5.4 set
to NONE. A warning will occur at 158F and higher, and an
alarm will occur at 168F and higher. If the stack temperature
is above the warning temperature, the boiler will be limited to
½ the called for input rate until the alarm temperature is
reached. At this point the boiler will shut down. The boiler
will then be allowed to restart when the Stack temperature
drops below 158F.

The version 3 control also supports an optional 1k platinum
stack sensor. If the Stack Sensor is present, a warning will
occur at 325F and greater. During the Warning condition, for
every degree F over the warning temperature of 325F, the

boiler’s input will be limited by 4% until the boiler is running

at low fire. If the SETUP: AUX FUNCTIONS: HEAT

EXCHANGER: ALARM TYPE: is set to” FAULT” the

boiler will halt and the Alarm relay will close when the Stack
temperature exceeds 350F. The boiler will then be allowed
to restart when the Stack temperature drops below 325F.

130

140

150

160

170

180

190

10 70

Water Temp

Outside Temp

WATER TEMPERATURE SETPOINT

OPTIONAL FEATURES HeatNet Control V3

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The Stack sensor should be a 1k ohm platinum type sensor.
Part # 0040-1300. To configure the 1k PT Stack sensor,
Switch S5.3 should be set to the NONE position and S5.4 set
to PLATINUM STACK. The sensor will then be auto­detected after a power cycle.

Security

A password can be used to lock out control and setup
features. It can be enabled, but is shipped in the disabled state

Save/Restore Configuration
Settings

(Firmware V2.0 or greater)

In a complex system, there can be a multitude of settings
necessary for proper boiler operation. These settings can be
saved to the onboard memory. ADVANCED SETUP:
LOAD DEFAULTS: CONFIG? SAVE.

Saving to the on-board memory is useful when the setup of
the boiler operation is complete, prior to upgrading firmware,
or performing a factory reset.

After a factory reset or firmware update the saved settings
can now be restored. ADVANCED SETUP: LOAD
DEFAULTS: CONFIG? RESTORE.

USB Features

The HeatNet V3 control supports a USB updating system and
desktop connectivity using the HeatNet Control Pro software.

In order to ensure that a valid firmware file is always
available on the HeatNet board, (2) file storage locations are
available. A firmware file is loaded at the factory in both
locations. This is to ensure that if a bad file is loaded by the
user, the factory loaded file can be re-loaded to get the board
functional again.

The firmware loading menu is located at; ADVANCED
SETUP: SYSTEM: LOAD FIRMWARE. The following
explains the menus.

Selecting USB DRIVE will read the FIRMWARE directory
on a flash drive and display any .hex files located there. The

USB flash drive needs to have a directory called “firmware”

located in the root directory. The downloaded firmware .hex
file needs to be placed there. Then the flash drive needs to be
inserted intoJ6 on the HeatNet control board. Follow the on
screen prompts and then select the file using the arrow keys.
Once a file has been selected, a STORAGE LOCATION
needs to be selected. There are (2) storage locations for the

new file. Location 1 is used for normal updates and Location
0 is for the factory stored backup file. When the Storage
location (default is Location 1) is selected the file will be
loaded into a permanent storage memory location. Next, the
control will reboot and copy this new program into running
memory, reboot, load factory defaults, and then reboot again.

Selecting USB CABLE requires connecting a USB cable and
running the Firmware Update program from a PC. This process
takes much longer and requires a Personal Computer (laptop) to be
taken to the boiler site. Again, follow the on screen prompts to down
load the program into a storage location as done when using the
above USB DRIVE loading menu. You will need the HeatNet Pro
software which can be downloaded from the website.

Selecting SAVE FILE will display the currently stored files in the
storage memory locations. Use the arrow keys to select a stored file
for copying to running memory. When SELECT is pressed the file
will be marked so it will be loaded on the next power cycle. Power
cycle the boiler to begin copying the file from stored memory to
running memory.

NOTE: to access the factory backup program, the P3

BOOT shunt on the HeatNet control board needs to be
connected and the CAL/NORMAL switch placed in the CAL
position. The BOOT jumper is located close to where the
ribbon cable for the display plugs in. If the control is power
cycled in this condition, the factory program will overwrite
the existing running program. If in the LOAD FIRMWARE
menus, STORAGE LOCATION 0 will be an allowed storage
location. When the download begins, remove the shunt from
P3 and slide the CAL switch to normal.

Saving/Restoring Settings

Selecting SAVE will store the setting in the on-board
memory in the event a firmware update is performed, a
factory reset needs to be done, or the settings are changed in
error and are unknown.

ADVANCED SETUP: LOAD DEFAULTS:
CONFIG?: SAVE

Selecting RESTORE will reload the saved settings.

ADVANCED SETUP: LOAD DEFAULTS:
CONFIG?: RESTORE

Diagnostics

The H-Net control can display and identify faults in a
meaningful way. If an interlock trips, it will be indicated in
the main screen display, along with an audible alarm
(mounted on control board) and a set of relay contacts will
close. A record of this, with a time stamp, will also be
entered into the log as an aide in the diagnosis of the event.
The log can be downloaded and a histogram used to display

OPTIONAL FEATURES HeatNet Control V3

Page 62

the data. If using Modbus, BACnet, or LonWorks, there are
software flag bits in registers available.

Open and shorted sensors are checked continuously, so that
in the event of a sensor failure, the system shuts down and
the alarm relay is closed.

If a pump fails (flow switch required), or the flow switch
fails, the boiler will cycle the start condition every 10
minutes in an attempt get the boiler restarted.

If the damper fails to open and never closes its proof switch,
a retry algorithm will attempt a retry. Every 10 minutes the
damper relay will cycle and try to open the damper again.

If the H-Net control closes the last interlock string connected
to the ignition control and the ignition control never closes its
Blower Relay, the H-Net control will wait 2 minutes. The H­Net control will then retry for the duration of the local pump
post purge time and then retry the ignition sequence. During

this time “retry strt” will be displayed in the status screen.

After (5) attempts the H-Net control will lock out and display
call service.

Communications

The H-Net control has the ability to communicate using the
MODBUS protocol with a building management system.
Most registers and functions are available for MODBUS
access. Access is allowed using the RS485 MODBUS PORT
connecter on the communication board. Version 2.x Control
has these connections integrated on the main board.

An optional BACNet or LonWorks bridge module can be
used to connect the MODBUS network (Default settings) to a
BACnet or LonWorks network. See Method 5 control.

Failsafe Modes

FAILSAFE MODES have been added to help protect
systems from loss of heat conditions. When using one of
these modes ensure that you connect any DAMPER
control, or system pump control to safely allow operation
with the assumption that the MASTER boiler or BMS system
is DOWN.

Failsafe Requirements:

1. Since the Member boiler that will be assigned the

Failsafe duty will always turn the system pump ON, this
boiler should not be used for DHW heating. If the
Master controls the system pump, then the Failsafe
Member boiler would need to control the system pump
in parallel with the Master boiler. Wire the System Pump
contacts in parallel with the Master.

2. If the combustion air damper is used as a common

system damper, the Failsafe boiler should be wired to
control the damper in parallel with the Master boiler.

3. The Failsafe boiler must have the LOCAL SETPOINT

set to the same setpoint temperature as the Master
boiler’s SYSTEM SETPOINT.

Be aware that the boiler may start without a call-for-heat in
the FAILSAFE MODES. FAILSAFE MODES can be
accessed through the:

SETUP: AUX FUNCTIONS: FAILSAFE MODES.
The following are types of Failsafe conditions.

1. Building Management System Failure

If a BMS system is controlling the setpoint and enabling
the boiler system, a timer is provided to allow operation
of the system in the event that communications are lost
with the BMS system. The HeatNet boiler system will
run locally if communications is lost and this timer
expires due to the lack of being updated.

The system setpoint timer and system setpoint work in
tandem to externally control (i.e. a BMS - building
management system) the operating setpoint. The
setpoint (countdown) timer should be loaded with a
timeout value (in seconds) prior to writing the system
setpoint. When the timer reaches zero, the control
assumes that the BMS is no longer operating and the
local setpoint (saved on the control) is reloaded. If the
setpoint timer is not written, a default timeout value of
60 seconds is assumed. This default time is adjustable
and the setpoint timer feature may be disabled in the
COMMUNICATIONS menu. The timer is automatically
reloaded with the default value when a setpoint is
written.

The BMS mode is always on and no menu

item is available.

2. HeatNet Communications Lost

SETUP: AUX FUNCTIONS: FAILSAFE MODES:
H-NET COMM LOST:

This mode allows a Member boiler to run in LOCAL if
the communications link via the H-NET cable is lost.
This includes the MASTER boiler losing its Control
board, Communications board, or the power on the
MASTER is switched OFF. When this MODE is set to
ON, and if the Member boiler loses its link (heartbeat
packet over the H-NET cable) to the MASTER Boiler,
this MEMBER will fire to the LOCAL setpoint.

The heartbeat packet over the H-NET cable

needs to be lost for 10 minutes.

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This MEMBER boiler will continue to run at the
LOCAL setpoint until H-NET communications from the
MASTER boiler is re-established.

Ensure that this Member boiler’s Damper and System

pump control are configured correctly with the
assumption that the Master is not powered. Also ensure
that any other System settings related to outside air
temperature sensing and system interlocks are set to
provide safe operation.

3. Domestic Hot Water Failsafe

If the DHW mode is set for Combination, a DHW
MEMBER boiler can be set up as a DHW Failsafe
boiler.

If a 10K sensor is used, connect to DHW TANK, J10 A,
9 & 10 of the Member Failsafe boiler. If there is only
one location for a 10K sensor, a dual sensor (14-0328, 4”
& 14-0329, 6”) is available that would be connected to
the Master and Member Failsafe boilers DHW TANK
sensor input. A jumper wire must be landed on the OR
OVR, J12A, 7 & 8 and JPS1 must be cut.

SETUP: AUX FUNCTIONS: FAILSAFE MODES:
H-NET COMM LOST: ON.

SETUP: DOMESTIC HOT WATER: DHW
BOILER?: COMBO. USE SENSOR: YES.

If an aquastat is used, connect it to OR OVR, J12A, 7 &
8 of the Member Failsafe boiler. If there is only one
location for an aquastat, then a dual aquastat must be
used. JPS1 must be cut.

SETUP: AUX FUNCTIONS: FAILSAFE MODES:
H-NET COMM LOST: ON.

SETUP: DOMESTIC HOT WATER: DHW
BOILER?: COMBO. USE SENSOR: NO.

Other DHW menu settings should be setup like the
Master boiler.

ADVANCED SETUP: DISTRIBUTED CONTROL:
MASTER TYPE: AUTO.

4. Low Temperature Protection

LOW TEMP: OFF, SUPPLY, HEADER, DHW, or
RETURN

This mode may be used by the MASTER or MEMBER
boiler and can be used as a type of freeze protection. In
this mode you may select which Sensor you wish to
monitor, or you may opt to turn this mode OFF. If you
select a sensor, you may then associate it with a
temperature at which the boiler will turn ON. Once the
temperature at this sensor falls below the LOW TEMP

temperature the boiler will start and fire to its LOCAL
setpoint. Once the Boiler reaches its setpoint it will turn
OFF.

Category 1 Venting

The version 3 control supports Category 1 Venting. If the
boiler is a Category 1 Venting version then the Category 1
Version of the firmware MUST be used, and the Category 1
Configuration resistor MUST be installed and wired to the J7
terminals. The configuration resistor is recognized
automatically. If the Category 1 resistor is not recognized the
boiler will not fire and the "CAT 1 BOILER CONFIG" fault
message will be displayed with a timestamp.

Please contact the factory for more information on Category
1 venting.

Limited Flow Boiler Control
Options

Three methods to limit the boilers based on flow are
provided.

1. Flow Limited Control (BMS)

2. Boilers Limited Control (BMS)

3. Flow Meter

The flow settings are used to limit HeatNet’s ability to add

boilers when the system flow changes. In variable flow
systems, and when the system flow is reduced, any boiler(s)
that is/are running may develop a high delta temperature
across the boiler. When this occurs, the boiler(s) will enter a
high delta T protection mode and drop to half of the rate
called for. At this time, the Master may not be able to achieve
setpoint due to the reduced output with the running boiler(s).
The Master will then call on more boilers to achieve setpoint,
but at the same time splitting the flow through the boiler(s) it
has running. The flow can be so reduced that the boiler(s) trip
their operating limits or even their high limits.

A flow meter input is supplied on the analog input 4-20 mA
(2). This input can be configured to capture flow in the
system that will be used to limit the # of boilers to fire. If a
flow meter and a System Return sensor are present, a BTU
load measurement will be displayed in the running screen
The BTU value is relative to the accuracy of the sensors and
is only available as an estimate of the BTU load. A
calibrated BTU meter would be required to get a more
accurate measurement.

The BTU load value may also be accessed through Modbus
read registers 30242 (upper 16 bit word) & 30243 (lower 16
bit word). These two words will need to be combined in
order to get the BTU load value.

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When using the BMS GPM register the BTU values are only
calculated to a whole GPM since the BMS GPM register
currently does not support floating point numbers.

The Building Management System (BMS) also has the ability
to limit the # of HeatNet boilers allowed to fire. When a
system has a fixed amount of boilers that HeatNet reports are
available, the BMS can limit the # of boilers that can fire.
The BMS can write the GPM value it has for flow, or directly
write a register with how many boilers HeatNet can control.
If the BMS GPM flow feature is active, the direct control
becomes inactive.

Using these features can limit HeatNet’s ability
to maintain setpoint.

1. Flow Limited Control: This method helps HeatNet to
limit the # of boilers firing based on the System Flow in

GPM. In variable flow systems, this will limit HeatNet’s

ability to add new boilers when insufficient flow is available.
The # of boilers allowed to fire is determined by:

Number of HeatNet boilers that can fire = BMS GPM Set

Rate/ LOWEST
FLOW

To activate this flow limited feature for use with a BMS:

a. Set ADVANCED SETUP: FLOWMETER:

FLOWMETER? YES

b. Set ADVANCED SETUP: FLOWMETER:

GLYCOL MIX: %. Currently, any mix over 10% de­rates the flow by 30% (rule of thumb method).
Example: if the LOWEST FLOW = 50 GPM,
HeatNet will calculate a New Lowest Flow required
to be 65 GPM. The LOWEST FLOW does not need
to be changed, but is calculated to 65 GPM and that
value is used by HeatNet.

c. Set ADVANCED SETUP: FLOWMETER: INPUT

TYPE to BMS.

d. Set ADVANCED SETUP: FLOWMETER: SET

PARAMETERS?

Enter LOWEST FLOW: (The automatic value loaded

will equal the lowest flow required for this boiler (it
is adjustable). It should be = to the lowest flow of the
largest boiler in the system).The HIGHEST FLOW &
FLOW FACTOR are currently not used with this
release. Once flow meter manufacturers have been
determined, new firmware will become available.

e. Write to address BMS GPM register 40019 with a

valid flow (0 -1500 GPM).

f. If a new GPM value is not written within 10

minutes, this feature will be deactivated until a
new flow value is written. Ensure periodic updates
of the flow register are done within 10 minute
intervals.

g. To check if HeatNet is in a flow limited state, read

the boiler status 4 register starting at address 30160

for the Master Boiler; if Status 4 bit (12) is set, it
indicates that the HeatNet control is running with
limited boilers due to insufficient flow derived from
the GPM value.

2. Boilers Limited Control: This feature allows the BMS to
directly change the amount of boilers that HeatNet can
control.

To Activate the Boiler limited feature:

b. Read Modbus address 30241 to see how many

boilers HeatNet has available to fire. MODBUS
AVAILABLE BOILERS register.

c. Determine how many boilers the BMS system will

require.

d. Write to address BMS LIMIT BOILERS register

40020 with the # of boilers HeatNet is allowed to
control (0 - 16).

e. If a new boiler # value is not written within 10

minutes, this feature will be deactivated until a
new boiler # is written. Ensure periodic updates
of the flow register are done within 10 minute
intervals.

f. To check if HeatNet is in a BMS limited state, read

the boiler status 4 register starting at address 30160
for the Master Boiler; if Status 4 bit (13) is set, it
indicates that the HeatNet control is running with
limited boilers due to the BMS system specifying
BMS LIMIT BOILERS being less than the available
boilers.

3. Flow Meter: Used to control the # of HeatNet boilers

allowed to fire. HeatNet will look at th e # of boilers it has
available, and the amount of system flow to determine how
many of boilers it can fire. As an Example: An Onicon F­1210 Flow Meter provides simultaneous 0-10V and 4­20mA outputs, so if the BMS system is using (1) output,
the other may be used by HeatNet.

To activate this flow limited feature for use with an Onicon
Flow Meter F-1210:

a. Set ADVANCED SETUP: FLOWMETER:

FLOWMETER? YES

b. Set ADVANCED SETUP: FLOWMETER:

GLYCOL MIX: % , Currently, any mix over 10%
de-rates the flow by 30% (rule of thumb method).
Example: if the LOWEST FLOW = 50 GPM,
HeatNet will calculate a New Lowest Flow required
to be 65 GPM. The LOWEST FLOW does not need
to be changed, but is calculated to 65 GPM and that
value is used by HeatNet.

c. Set ADVANCED SETUP: FLOWMETER: INPUT

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d. TYPE to mA 2 or VOLTS 2 depending on whether

a 4-20 milliamp or 0-10 volt signal is used. The
connection should be made from the Flow Meter to
analog input 4-20 mA (2).

e. Select ADVANCED SETUP: FLOWMETER: SET

PARAMETERS?

Enter LOWEST FLOW: (The automatic value

loaded will equal the lowest flow required for this
boiler (it is adjustable). It should be equal to the
lowest flow of the largest boiler in the system).

f. Set the ADVANCED SETUP: FLOWMETER:

FULL SCALE value to the full scale reading on the
calibration card that came with the flow meter.

g. The HIGHEST FLOW & FLOW FACTOR

currently are not used with this release.

h. These settings will use the equations:

4-20 mA:
Measured GPM = (signal/16) * FULL SCALE flow

0-10 Volt:
Measured GPM = (signal/10) * FULL SCALE flow

These settings may work with other flow meters

(consult their respective manuals).

HeatNet Online

HeatNet Online is a web based system for fault
notification, monitoring and tuning of a HeatNet based
system. A HeatNet Online bridge module is required to
connect a boiler (Usually the Master boiler) to the internet.
The bridge is available for version 2.x and version 3.x
HeatNet controls and is standard on V3.x, boilers equipped
with a touchscreen display. The bridge module provides an
RJ45 connector for access to the internet. If an RJ45
hardline is not available, a wireless modem can also be
used. Consult the factory or sales for available solutions.
The HeatNet Online site may be accessed at:

www.heatnet.net/ . A login Account/Password is

required.

Once a user has registered a site, the users email can be set
up to provide daily status messages and fault/alarm emails
within minutes of trouble. This provides a valuable tool for
technicians on the road. If the technician has a smart
phone, they can be notified through the emails on their
phone. They can then log on to the HeatNet Online website
(from their phone) to determine the trouble.

Sample email message:

HeatNetOnline Alert

Once the user has logged in, a selection screen for the
building sites the user has registered will be displayed.
When a building site is selected, the main “Live” screen
will be entered. This is the HOME screen and provides a
quick view on the status of the site.

Selecting the History tab allows a runtime Histogram of
the system. The histogram displays temperatures and states
of the system in a date/time format. Also displayed is the
Master boiler log, faults, messages, modulation, and
events. To the right of the histogram is the Master Boiler’s
log. Since the HeatNet bridge only transmits at 1 minute
intervals, the log can be used to precisely view the state of
the boiler at the time of the event (in-between minutes).

OPTIONAL FEATURES HeatNet Control V3

Page 66

This screen is an excellent way to diagnose system
problems and tune systems for optimal performance.

Data Points can also be viewed in a manner other than a
histogram as pictured below. The date/time picker can be
used to mine the raw data stored on the HeatNet Online
server.

Runtime graphs of each boiler ensure even runtimes are
being observed by a properly operating system.

This is just an overview of HeatNet Online and a few of
the screens that are available.

Wiring Connections

Figure 48 Dip Switches and Wiring

Wire Strip Length.

If the terminal blocks are of the screwless type, the wire should be stripped to .42” or 10.67mm.

If the terminal blocks are of the screw type, the wire should be stripped to .25” or 6.34mm.

WIRING CONNECTIONS HeatNet Control V3

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Figure 49 Jumper & Dip Switch Locations

WIRING CONNECTIONS HeatNet Control V3

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Figure 50 Heating Method 1 H-Net, Master/ Member

Figure 51 Boiler Terminal Block

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Figure 52 Heating Methods 2 and 4: AA-High Fire and High/Low, Master or Member boiler

Heating Mode 2: Stage Control Inputs.

T1 or T2 Closed: Lowfire
T1 & T2 closed: Highfire

T1 T2

Heating Mode 4: High Fire

Close this contact to run boiler at Highfire.

WIRING CONNECTIONS HeatNet Control V3

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Figure 53 Heating Method 3 4–20 mA / 0-10 VDC

Figure 54 Boiler Terminal Block

WIRING CONNECTIONS HeatNet Control V3

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Figure 55 Heating Method 5: MODBUS (Optional BACnet or LonWorks bridge — Protocessor)

http://rbiwaterheaters.com/resource-center/technical-library/

WIRING CONNECTIONS HeatNet Control V3

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Figure 56 Relays, Interlocks and Boiler Status

The Highest priority

Low Voltage
Interlocks, 24VAC

Factory ------------------------------

Water Flow Switch-----------------

Operator------------------------------

Spare for user or Factory ------

Gas Pressure (High & Low) -----

Variable Frequency Drive--------

Low Water Cutoff-------------------

SYSTEM FLOW PROVE ---------

1
2
3
4
5
6
7
8

Low Fire Hold: Fires the boiler at
the minimum rate while in
Calibrate. This functions exactly
as the T1 input

Calibrate: Allows adjustment of
the Minimum Fire, Maximum
Fire, and Pilot Ignition settings.

Combustion proving switch
from Combustion Air Damper.

Remote 120 VAC
Operator

USB and Flashdrive Ports:

Used by HeatNet Pro and
updating firmware.

Local Pump or

Power Open/ Power Close Valve

DHW Pump or

Power Open/ Power Close Valve

Stage Control

Damper Control

Alarm

JUMPER
WIRE if
not used

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Figure 57 Temperature sensors

WIRING CONNECTIONS HeatNet Control V3

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Figure 58 Typical Single Boiler System

#4

#3

#2

#1

#8

#14

#7

#11

#9

#10

#5

#13

#12

IGN Control

Connections

High Limit

Heat Demand*

*Note: When using DHW

MASTER? YES, a Heat Demand

signal must be used to activate

the system.

HEADER SENSOR

(Determines Master Boiler) #4

RETURN

SENSOR

#3

SUPPLY

SENSOR

#2

LOCAL PUMP

ENABLE #8

FLOW PROVE

#10

SYSTEM PUMP

ENABLE #14

FLOW PROVE #9

OUTDOOR

SENSOR

North Away

From Exhaust

#1

BOILER

DHW TANK

DHW PUMP

ENABLE #12

DHW TANK

SENSOR #5*

DHW TANK

AQUASTAT #13

DHW RETURN

DHW SUPPLY

COMBUSTION AIR

DAMPE R

ENABLE #7
PROVE #11

WIRING CONNECTIONS HeatNet Control V3

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Figure 59 Using a 4–20mA signal for direct modulation

100%

Boiler Output

0%

Boiler Off

Ignition

100%

0%

Percent of Boilers

Output

Percent of Boilers

OUTPUT

Ignition

4mA 20mA

Control Signal

Output Range From

Control

No Effect

Once boiler starts the
control signal must
drop below 4.01 mA
to stop Boiler

MAX

OUTPUT

After Ignition

0%

100%

Control Signal to MAX Output

Boiler Off

Percent of Boilers

INPUT

0ma

Display input % of control when running

A control signal greater
than 4.2mA (adjustable)
will start boiler.

PWM Duty Cycle

Blower Off

20%

Blower Fully ON

80% 100%

0%

20% = the

minimum speed

the VFD will run

20% for 5:1 boilers
25% for 4:1 boilers
33% for 3:1 boilers

33%

20%
25%

33%

20%
25%

20% for 5:1 boilers
25% for 4:1 boilers
33% for 3:1 boilers

Boiler Off

WIRING CONNECTIONS HeatNet Control V3

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Figure 60 Common system damper wiring

DAMPER

24 VAC Ret

DAMPER 24 VAC

Transformer

DAMPER

Prove Switch

DAMPER

Enable

24 VAC

Mains

MASTER BOILER

MEMBER BOILER 1

Connection if Member

boiler is running as

Failsafe

MEMBER BOILER 2

Connect to 24 VAC Return

on each Boiler

NOTE: Ensure that the Combustion Air

Damper is enabled on all Boilers for use.
SETUP MENU:AUX FUNCTIONS

WIRING CONNECTIONS HeatNet Control V3

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Figure 61 Failsafe common system pump wiring

System Pump

Contactor

System Pump Voltage Feed

System Pump

System Pump

Voltage Return

120VAC

Ph2
Ph3

120 Return

120 VAC Return

DPST
Relay

System Flow

Prove Switch

120VAC

Add additional relays/

contacts for more boilers

MASTER BOILER

MEMBER BOILER 1

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* Status Information

Whenever an * is displayed on the RUN screen it indicates that there is more information available about the current running
conditions. This information can be viewed by going to the *STATUS screen as shown on the previous page. For more
information on the parameters discussed here please see the Default Settings & Menu Item Descriptions — SETUP, starting on
page 88.

Status information screens

This screen indicates that the boiler’s SUPPLY

Temperature has gone above the OPERATOR
LIMIT. This will mainly be seen on Member
boilers to show why they are not available to fire.

This screen indicates that the boiler’s SUPPLY
temperature has risen inside the OPERATOR LIMIT
BAND.

This screen indicates the boiler’s input is being

limited by the MOD-MAX value to optimize system
efficiency. This will only be seen on a MASTER
boiler.

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Status information screens

This screen indicates the control is attempting to re­initiate the ignition control because the ignition
control did not begin PRE-PURGE. For more
information see CALL SERVICE LOG entry.

This screen indicates that the boiler’s has received a
heat demand, but its MINIMUM OFF time has not
expired.

This Screen indicates that the boiler’s input is
temporarily being limited to optimize the boiler’s

efficiency.

This screen indicates that the boiler is running in
LOCAL MODE because it has lost H-NET
communications with the MASTER, and the failsafe
mode has been activated.

This screen indicates the DHW: MAX RUNTIME
(adjustable) has exceeded its limit. The programmed
DHW: HOLDOFF time (adjustable) is now in effect.
During the hold off time the system is now able to
satisfy a space heating call then release back to the
DHW demand when the hold off time has expired.

WIRING CONNECTIONS HeatNet Control V3

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Status Screen Fault Display

There are numerous interlock switches and software limits that are detected. Each of these, when tripped will produce a display
message, an audible beeping, and an alarm relay closure. The fault is displayed first, then after a second, the time the fault
occurred is displayed. This cycle will keep occurring until the fault is cleared.

These faults and interlocks are:

HIGH LIMIT:

When the high limit aquastat trips the following message is
displayed:

The high limit interlock breaks power to the ignition control
(shutting it off) and effectively removes any chance of the
gas valve receiving power. The HeatNet series control will
remain powered to display the fault, latch the alarm
relay/audible beeper, and to access the log. The interlock is
located on J5, HIGH LIMIT. Ensure power is present on the
input to the High Limit Control.

SPARE 4:

This is a reserved interlock input that is user defined. The
interlock is located on J5B, SPARE 4.

DELTA TEMPERATURE WARNING:

If the temperature difference across the boiler measured
from RETURN water to SUPPLY water exceeds the
EXCHR DELTA T RANGE, setting this message will be
displayed.

LOW WATER CUTOFF:

If there is a low water condition reported by the low water
cutoff switch this fault is displayed. Check that there is
water flow and water in the boiler. There is a reset switch
located on the LWCO box. The interlock connection is
located on J5B, LWCO.

VAR FREQ DRIVE:

The variable frequency drive, which controls the blower, if
supported, reports this fault. It may be caused in the event of
over current or an internal VFD fault that would cause it to
shut down. If this is the case, check the fault indicators on
the VFD. The interlock is located on J5B, VFD.

GAS PRESSURE:

The gas pressure switches (high pressure and low pressure)
are connected in series, so if either trip, a fault will be
reported here. A reset switch is located on the gas pressure
switches. The interlock is located on J15B, GAS PR.

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SYSTEM WATER FLOW:

Once the HeatNet series boiler receives a call for heat, it
closes the system circulator pump relay. It then waits 10
seconds or more (adjustable) to prove flow. If there is no
flow, the flow switch alarm will be set. Every 10 seconds
the circulator pump relay will cycle ON for 10 seconds and
then OFF for 10 seconds to try and establish flow. The
interlock connection is located on J5B, SYSTEM WTR
FLOW.

WATER FLOW LOCAL:

Once the HeatNet series boiler receives a call for heat, it
closes the LOCAL PUMP/VALVE relay. It then waits 10
seconds or more (adjustable) to prove flow. If there is no
flow, the flow switch alarm will be set. Every 10 seconds
the circulator pump relay will cycle ON for 10 seconds and
then OFF for 10 seconds to try and establish flow. The
interlock connection is located on J5B, WTR FLW.

IGNITION CTRL ALARM:

The ignition control alarm is displayed if the ignition
control detects a fault. This could be a flame failure, air
proving switch, or other fault associated with the ignition
control. When this fault occurs, you will need to refer to the
ignition control for the reason.

COMBUSTION AIR DAMPER:

If the combustion air damper has been selected for use
(AUX FUNCTIONS), and the proof switch does not make,
this fault will be displayed.

When the Master boiler receives a call for heat and needs to
start a boiler, the DAMPER relay closes on J13. If the
combustion air damper does not prove within the proof time
specified in the combustion air damper menu, the boiler will
not start and then display the fault. A combustion damper
fault on a boiler can only be cleared by power cycling.

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OPEN ******* SENSOR:

If the open sensor fault is displayed, the sensor in the
position reported was originally detected, but has since
opened. The boiler will shut down on any OPEN sensor
except the OUSTSIDE AIR sensor.

SHORTED ******* SENSOR:

If the shorted sensor fault is displayed, the sensor in the
position reported was originally detected, but has since
shorted. The boiler will shut down on any SHORTED
sensor except the OUSTSIDE AIR sensor.

AIR SWITCH:

If the IGNITION control closes its blower relay, the control
does not see the PILOT relay close within (2) minutes, and
the AIR PRESSURE switch is made, this message will be
displayed. This alarm protects the boiler from freeze ups
being caused by a blower bringing in cold outside air with
no fire. It usually indicates that the blower never started or
the air switch never closed.

CALL SERVICE:

If the H-Net control closes the last interlock string entering
the ignition control and the ignition control never closes its
Blower Relay, the H-Net control will wait 2 minutes. The
H-Net control will then retry for the duration of the local
pump post purge time and then retry the ignition sequence.

During this time “retry strt” will be displayed in the status

screen. After (5) attempts the H-Net control will lock out
and display call service.

DELTA TEMPERATURE WARNING:

If the temperature difference across the boiler and measured
from RETURN water to SUPPLY water exceeds
“EXCHGR DELTA” this message will be displayed. This
can be set to an alarm condition in the AUX FUNCTIONS
menu. High delta temperatures can result in damage to the
boiler.

Calibration HeatNet Control V3

Page 83

Calibration

The calibration of the Futera III/Fusion-

Series boiler should only be performed
by a licensed technician.

To enter the calibration menus, place the S2 switch on the
main control board to the CAL position.

Be sure to set this switch back to NORM when the
calibration is complete, otherwise no external control inputs
will work (except T1-T2), the display will always indicate
CALIBRATE and some of the runtime temperatures will
not be displayed.

The MINIMUM VFD setting, the MAXIMUM VFD
setting, and the Ignition setting can be adjusted in the
calibration displays. The values can be changed while
running ONLY IN MINIMUM FIRE (any, but only one of
the T inputs closed). Prior to ignition, the values may be
changed, but the blower will not operate.

The Low Fire Hold switch is located near the

Calibration switch.

Press the arrow keys until MIN VFD is shown in the
display, along with the minimum percentage value at which
the boiler is to run at min fire. While in Standby (no call for
heat on inputs), the minimum percent may be preset. To set
the minimum rate while running, any (1), and only (1) of the
(T) inputs must be closed in order to set the boiler to
MINIMUM fire. Press the SELECT key for approximately
1 second. The Percentage value will start flashing,
indicating that it can be adjusted. Adjust the Minimum value
to the desired setting using the arrow keys. The Minimum
setting is clamped to its lowest rated setting and cannot be
adjusted below this. Once you are done with this setting,
press the SELECT key until the value stops flashing. The
new setting is now saved.

Press the Arrow key to select the IGNITION percent. The
Blower speed will be set here to provide the rate for
ignition. While in Standby (no call for heat on inputs), the
Ignition percent may be preset, before firing the boiler. To
set the ignition rate while running, any (1), and only (1) of
the T inputs must be closed Pressing the SELECT key here
will cause the IGNITION setting to flash and the boiler will
ramp to the ignition setting. Adjust it using the arrow keys
and then press the SELECT key until the value stops
flashing. The new setting is now saved.

LOG ENTRY HeatNet Control V3

Page 84

Log Entry

To access the Log Files, press and hold, the “Back” button
for 5 seconds, the control will beep once. There are three
menu options, SETUP, ADVANCED SETUP, and VIEW
LOG. Place the curser in front of the VIEW LOG menu
item and press “Select”.

The Futera III/Fusion-Series H-Net control contains a log
that records the major activity (events) in the operation of
the boiler. This activity includes interlock faults, boiler
starting and stopping events, power cycles, misc. faults, and
types of calls-for-heat (control inputs). Setting the time
clock to an accurate time and date is very useful when
events are recorded, since the control will time stamp each
snapshot. If the system is configured to run with HeatNet,
then only the Master boilers SYSTEM TIME needs to be
entered. The Master will then set the time on all Member
boilers.

The log is primarily used as a troubleshooting and
diagnostic tool, but may be used as a performance tool to
view run time cycles.

An event in time of the boiler’s state is presented via
multiple screens. Each screen event can be stepped through
using the arrow keys.

The top line displays the time and date the event occurred.
In the top right corner, the event # is displayed so that easy
indexing can be done using the arrow keys. The second line

displays the Water temperature of the boiler’s output

(supply) and the Setpoint temperature. The third line
displays the Outside Air temperature, and the Modulation.
The bottom line is used to record the control state of the
boiler.

The control state is defined as the Boiler(s) that is running,
the Circulator Pump state, and the ignition condition (Main
Valve, Pilot Valve, Blower, and the Ignition alarm). The #
of boilers that are displayed is limited to 7 if the boiler is the
MASTER. If boilers #8 and up need to be viewed, the
Boiler Control Pro software will need to be used. The Last
2 characters on the fourth line indicate the heating mode the
control is in. The modes are:

NC = No Call for Heat
HD = Heat Demand (MASTER and Local modulation

control using PID control, MASTER and

MEMBER)
RM = Remote Modulation from 4-20mA input
HF = High Fire from ALL T-inputs closed or the AA

input
1T = Low Fire from any 1 T-input closed (Low Fire or

High Fire)
2T = Mid Fire from any 2 T-inputs closed (Low fire or

High Fire )
OP = Option input Active
HT = H-Net Control using the Heat-Link

communications cable

The bottom line is also used to indicate an interlock or limit
that has tripped. It may also indicate a sensor that has failed.
When this occurs, the normal bottom line in the display is
not visible, and the sensor fault is displayed.

For details on messages that appear on the fourth line: See
Appendix B.

The log may also be viewed using HeatNet Pro or HeatNet
Online.

Figure 62 Log entry display

Time

Stamp

Event

number

Water Setpoint

Modulation PWM %

M = Main Valve open

P = Pilot Valve open

B = Blower ON

P = Circulator Pump

Boiler 1 On

Boiler 2 On

Boiler 3 On

Outside Air

Temperature

NC = No Call for Heat
HD = Heat Demand
RM = Remote Mod 4-20ma
HF,1T, 2T, 3T = T-inputs Fire Rates
HT = H-NET Control

H= Honeywell Alarm

Boiler 7

S = System Pump

D = DHW Pump (Ver 2.x control)

SET

:0 5 :4 2 P

H2O 127° F

MOD%

1

3

1 0 / 14

13

OA

65° F

140° F

57

P

- - - - - -

H HD

M

PB

LOG ENTRY HeatNet Control V3

Page 85

Line 4 Log Entries:

To access the Log Files, press and hold, the “Back” button for 5 seconds, the control will beep once. There are three menu
options, SETUP, ADVANCED SETUP, and VIEW LOG. Place the curser in front of the VIEW LOG menu item and press

“Select”.

The following table lists the messages on line # 4 of the log’s display.

Line # 4 Message

Description

SETBACK IS ACTIVE

SETBACK EXPIRED

If any of the (4) temperature setbacks are active these log entries will be
displayed in the log.

NO LOCAL FLOW
NO SYSTEM FLOW

If the test for flow fails these log entries will be displayed. The flow proving
switches are wired to J11A and J11B.

COMBUSTION AIR FAIL

If the combustion air damper is used and does not prove across J10B
DAMPER or J12B DAMPER, this message is displayed.

SYSTEM RESET -- ----

O: stack overflow,
U: Stack Underflow ( both are software faults)

R: Reset Instruction ( Firmware or Default load),

W: Watchdog ( Firmware code ran erroneous code and
rebooted),

P: Power-ON (Power switch toggled),

B: Brown-out ( Microcontroller saw a voltage less than 4.5
VDC)

When the control is reset, this log entry captures the reason the reset occurred.

LOG ENTRY HeatNet Control V3

Page 86

Line # 4 Message

Description

OUTDOOR RESET

This log entry indicates that Warm Weather Shutdown is in effect.

HIGH DELTA TEMP

This log entry occurs when the temperature across the heat exchanger has
been greater than the EXCHR DELTA T RANGE degrees F.

SHUTDOWN UV TEST

After 24 hours of continuous runtime the ignition control module needs to
check its UV detection circuit. An orderly shutdown and then a restart will
occur. This log entry indicates that this has taken place. This is not a fault.

HIGH LIMIT EXCEEDED

If the mechanical thermostat trips due to its high temperature setting having
been exceeded, this log entry will occur.

IGNITION CTRL ALARM

The ignition control module has faulted while performing an ignition
sequence, or while monitoring flame during normal operation.

IRI Alarm

If the gas valve proving circuit (if equipped) detects a gas pressure problem.

DOMESTIC HOT WATER

Indicates a call for DHW heating by either the DHW sensor or an external
thermostat.

LOW WATER CUTOFF
VAR FREQ DRIVE
GAS PRESSURE
SPARE 4
OP LIMIT MECH

These log entry faults are result of the interlocks connected to the 24VAC
interlock inputs: J11A and J11B.
Low Water Cutoff = Low water condition in boiler
Var Freq Drive = The blowers Variable Frequency Drive has a problem
Spare 4 = User installed interlock,
Op Lim Mech = An external operator (aquastat).

START FAILED, RETRY

If the H-Net control closes the last interlock string entering the ignition
control and the ignition control never closes its Blower Relay, the H-Net
control will wait 2 minutes. The H-Net control will then retry for the duration
of the local pump post purge time and then retry the ignition sequence. During
this time “retry strt” will be displayed in the status screen. After (5) attempts
the H-Net control will lock out and display call service. The Log will report
the retries.

OP LIMIT REMOTE

The OPERATE LIM is the firmware Operating Limit as defined in SETUP:
SETPOINTS: OPERATE LIM. When the Supply temperature exceeds this
value, this event is logged.

OPEN OUTSIDE SENSOR,
SUPPLY SENSOR,
RETURN SENSOR,
HEADER SENSOR,
DHW SENSOR

If one of the 10k thermistor sensors was detected to be open or not connected,
this fault will be logged.

LOG ENTRY HeatNet Control V3

Page 87

Line # 4 Message

Description

SHORTED OUTSIDE SENSOR,
SUPPLY SENSOR,
RETURN SENSOR,
HEADER SENSOR,
DHW SENSOR

If one of the 10k thermistor sensors was detected to be shorted this fault will
be logged.

AIR SWITCH(BLOWER)

If a call is made to the ignition control to start and the HeatNet control detects
a blower start, but no Pilot within two minutes, the boiler locks out. This log
entry indicates that the blower was ON with no flame in the boiler. Freeze up
protection.

LOST BOILER #
FOUND BOILER #

These log entries indicate that HeatNet has either discovered a boiler or lost a
boiler using its auto detection algorithm.

FAIL SAFE H-NET LOST
FAIL SAFE LOW TEMP

If the Fail Safe modes are active, these log entries indicate that they became
active for some reason and the boiler had entered Fail Safe mode.

BASE LOAD BOILER

The Base load Boiler Relay K8 is Active if ON
Inactive if OFF

CALL SERVICE

If the H-Net control closes the last interlock string connected to the ignition
control and the ignition control never closes its Blower Relay, the H-Net
control will wait 2 minutes. The H-Net control will then retry for the duration
of the local pump post purge time and then retry the ignition sequence. During

this time “retry strt” will be displayed in the status screen. After (5) attempts

the H-Net control will lock out and display call service.
#BOILERS LIMITED

The # of boilers that can fire is limited due to flow or the BMS.

1/2 RATE DELTA T

When the temperature across the heat exchanger has been greater than the
EXCHR DELTA T RANGE degrees F.

DEFAULT SETTINGS & MENU ITEM DESCRIPTIONS HeatNet Control V3

Page 88

Default Settings & Menu Item Descriptions — SETUP

To enter the Settings Menu, press and hold, the “Back” button for 5 seconds, the control will beep once. There are three menu
options, SETUP, ADVANCED SETUP, and VIEW LOG. Place the curser in front of the menu item and press “Select”. Once a
setting is changed, the select button must be pressed to save the setting.

SETUP

DEFAULT

VALUE

RANGE

DESCRIPTION

BOILERS

# OF BOILERS

1

1-16

If operating as a Member.

LEAD BOILER #

0

0- 6

# of first boiler to run, determines the fire order in rotation. A

LEAD BOILER #

0

0-16

# of first boiler to run, determines the fire order in rotation. A 0
disables the Lead Boiler function. Firing Mode determines lead.

HEAT BAND

30F

2-50 F

Differential temp around setpoint used to stage boiler(s) OFF/ON

HNT

M

M-16

This line displays the boilers auto detected by H-Net. While M is the
Master boiler the numbers are the H-Net address of each boiler from
2–16.

SETPOINTS

LOCAL SETPT

160 F

40-220 °F

Local setpoint used to maintain temperature of SETPT SOURCE

OPERATE LIMIT

215 F

45-230 °F

When running as a Member, boiler shuts off when supply
temperature reached.
Boiler restarts at lower temp of OP LIM BAND or 10F whichever is
lower

LOCAL SETPT

160 F

40-220 F

Local setpoint used to maintain temperature of SETPT SOURCE

OP LIM BAND

20F

1-50 F

Limits external input % when in (OP LIM - OP LIM BAND)

SETPT SOURCE

AUTO

AUTO

4-20mA

AUTO = Local/ System/ WWS Setpoint is used
4-20mA input is mapped to a setpoint.

OUTDOOR AIR RESET

OA RESET

OFF

Outdoor reset ratio (boiler water temp/outside air temp).

WARM WEATHER SD

NO

If set to YES, the boiler /system shuts down when the temperature
exceeds the WWS SETPOINT.

WWS SETPOINT

68F

40 – 100 F

Temperature at which boiler shuts down, operation is below this.
If boiler is running using either OA RESET or WWS and the OA
OVR input is closed the OA RESET slope is overridden and runs at
local setpoint until OA OVR input opens.

SET OA SETPOINTS

WATER TEMP

At

HIGH OA TEMP

140F

60 – 190 F

Boiler water temp setpoint when OA temp is at HIGH OATEMP
These four setpoints determine the OA reset slope.

WATER TEMP

At

LOW OA TEMP

10F

-35 – 40 F

Header/Supply setpoint when OA Temp is at LOW OA TEMP

PUMP OPTIONS

SYSTEM PUMP

POST PRGE TIME

2 minutes

2-60min

Time in minutes to keep system circ. pump on after boiler stops

PUMP ROTATION

New menu screen

ROTATION:

NONE

NONE

SYS HRS

PUMP HRS

SYSTEM PUMPS

1

1 or 2

The number of system pumps. Only 1 available in Lite version.

DEFAULT SETTINGS & MENU ITEM DESCRIPTIONS HeatNet Control V3

Page 89

ROTATE TIME

240 hrs

1-1000 hrs

If ROTATION is set to SYS HRS, ROTATE TIME is used to switch
pumps when this time expires. This time is measured against the
actual time the system pump is enabled. This would include a post
purge time.

If ROTATION is set to PUMP HRS, ROTATE TIME is used to
switch pumps when the pump’s time difference is greater than
ROTATE TIME. Whichever pump has the least time and is at least
below the other (pump’s time - ROTATE TIME) will switch to the
enabled state. This selection is used to equalize run time on the
pumps.

MORE MENUS

New menu screen follows.

ZERO RUNTIME

PUMP1

PUMP1- PUMP2

This menu allows the clearing of a pump’s runtime counter.
Discretion is advised in clearing only one pump’s hours after
replacement and then using ROTATION set to PUMP HRS. This
would cause the pump whose runtime was cleared to run until its
time exceeded the other older pump.

PUMP1 TIME

0-999999 hrs

Indicates how many hours the HeatNet control has accumulated on
pump 1.

PUMP2 TIME

0-999999 hrs

Indicates how many hours the HeatNet control has accumulated on
pump 2.

ALWAYS ENABLED

OFF

ON/OFF

ON = Pump never shuts off. Used when there is only 1 system pump
in the system.

SUMMER PUMP JOG

OFF

ON/OFF

MON-SUN

Used with Outdoor Reset, Jogs the local and system pump(s) for
POST PRGE time when system is in summer shutdown. Jog once a
week @12:00 AM.

The menu item OVR ENAB IN WWS and ALWAYS ENABLED
must be set to OFF for the jog function to work,

OVR ENAB IN WWS

OFF

ON/OFF

Priority mode for the system pump while in Warm Weather
Shutdown. ON: The system pump is allowed to run in WWS when
the OR OVR override input is closed. When set to OFF, the system
pump will not come on while in WWS with the OR OVR override
input closed. Enabling this feature disables the SUMMER PUMP
JOG.

LOCAL PUMP

DELTA TEMP ENAB

OFF

ON: Use Delta temperature to shut pump off when temperature
across boiler is less than DELTA TEMP setting.

DELTA TEMP

10 °F

2 – 50 F

POST PRGE TIME

2 minutes

1-60min

Time in minutes to keep local circ. pump on after boiler stops

ALWAYS ENABLED

OFF

Pump never shuts off.

PUMP/VALVE OPTIONS

MASTER PUMP/VALVE

REMAINS ON:

OFF

ON/OFF

ON: The Master boiler will keep its pump/valve on when no boilers
are running. Prevents deadheading the system flow.

LOCAL PUMP VFD

OFF

ON/OFF

ON: Outputs a 0-10VDC or 4-20mA signal from J4 pins 1 & 5 that is
proportional to the fire rate of the boiler. Connect to a VFD
controlling a Local pump.

FLOW PROVE

10s

10-240 sec

This is an adjustable flow proving time to allow slower valves to
open before proving flow.

NIGHT SETBACK

SETBACK ENTRY

1

1 – 4

Four setbacks to adjust setpoint during a time period

ENTRY IS

OFF

Enable or disable the use of this setback

SETBACK

20 F

0 – 50 F

Temporarily subtracts this temp from the setpoint

DEFAULT SETTINGS & MENU ITEM DESCRIPTIONS HeatNet Control V3

Page 90

START DAY

MON

Day of the week to begin setback or a day range

TIME

12:00AM

Time to begin setback

END DAY

MON

Day of the week to end the setback or a day range

TIME

12:00AM

Time of the day to end the setback

OPTIONS

TEMP SCALE

F

F or C

Fahrenheit scale is default

KEY CLICK

ON

Beeps when a key is pressed

SKIP PASSWORD

ON

Disables the Password

BRIGHTNESS

50%

25, 50,75,100

Four levels of display brightness, lower for longer life of the display

LOG/RUNTIME

RUN HOURS

Displays runtime hours. Total time the main valve has been open.

DATA LOG ENTRY

Displays the current entry in the data log

SIZE

Displays the current size of the log in entries

BOILER CYCLES

Displays completed boiler cycles. Incremented when the main valve
turns OFF after it has been ON. Does not include attempts to light.

AUX FUNCTIONS

COMBUST AIR
DAMPER

TYPE

LINKED/COMMON

INDEPENDENT

The LINKED/COMMON setting allows one common damper to be
used and controlled by the Master Boiler. All Member boilers must
have their damper prove inputs wired as per Figure 60, Common
system damper wiring, page 76. Also see Section: Optional
Features: Auxiliary Function Options INDEPENDENT: Individual
dampers are in controlled by their respective boiler.

IN USE?

YES

If set to YES, then OUTPUT RELAY K5 can be used to control a
combustion air damper. The Master can control a common system
damper or an individual damper. Members control their respective
damper independent of the Master. Relay K5 is used to enable the
combustion air damper. See Figure 60, Common system damper
wiring, page 76. Needs to Prove the damper is open.

INPUT:

J12B.7

DAMPER

The damper prove input is dedicated to connect at J12B terminals 7
and 8. If using a common damper refer to the common damper
wiring diagram.

PROOF TIME

2:00

0 – 4min

This is the proving time in minutes for the combustion air damper
prove switch. It is sensed at J12B Pin 7. If the damper faults, a retry
will occur every 10 minutes in attempt to open the damper.
When using J12B in a common damper configuration, wiring is done
beginning with the Master boiler. J12B Pins 7 & 8 are connected to
the prove switch of the combustion damper. Pin 8 is supplying 24
VAC and pin 7 is the sense input. A second wire is connected to
J12B pin 7 of the Master and the other end connected to the first
Member boilers J12B pin 7. If another Member boiler is present,
connect another wire to the J12B Pin 7 terminal of the first Member
and the other end to the second Member boiler J12B pin 7. Continue
this method for each additional boiler.

ALARM SILENCE

ALARM SILENCE IN

USE?

YES

This menu allows the configuration of the Alarm Silence switch. It
can be disabled so that the Alarm Silence switch cannot silence the
alarm until the alarm is cleared; ALARM SILENCE = NO. The
default value is to enable the ALARM SILENCE switch. Holding
down the BACK and SELECT keys at the same time may also be
used to silence the alarm.

INPUT =

J10B STACK

If a stack sensor is used, holding down the BACK and SELECT keys
at the same time is the only way to silence the alarm.

DEFAULT SETTINGS & MENU ITEM DESCRIPTIONS HeatNet Control V3

Page 91

FAILSAFE MODES

RUN IN LOCAL IF:

H-NET COMM LOST

OFF

If this entry is set to ON and the Member boiler does not see any
communications coming from the Master boiler, this boiler will run
in LOCAL. The boiler will continue to run in LOCAL until
communications are re-established or this entry is set to OFF.

LOW TEMP

OFF

This entry may be set to one of the temperature sensors: SUPPLY,
HEADER, RETURN, or turned OFF (default). If this entry is set to a
sensor and the temperature falls below TEMP, the boiler will
automatically start and run the water temperature up to the LOCAL
Setpoint and then shut OFF.

TEMP < 40F

40 F

35-200 F

This is the temperature that the selected sensor must fall below for
the boiler to start.

HEAT EXCHANGER

ALARM TYPE

WARNING

FAULT/WARNING

FAULT will stop the boiler when the Delta T has exceeded its
setting.

WARNING will allow the boiler to continue running, but produce
the Warning message.

EXCHR DELTA T

40F

Per Boiler

This is the maximum differential temperature the heat exchanger can
see before the LIMIT RATE feature is activated, and a log entry is
made.

LIM-> HALF RATE

YES

Limit to Half Rate: When set to YES, and the maximum differential
temperature (delta T) has been exceeded, the fire rate called for is cut
in half. If we are calling for 80% modulation and have exceeded the
delta T, the boiler will only fire at 40%. The delta T needs to drop
10F below the maximum delta T to reset this limit. The message “½
INPUT” will be displayed on a Member boiler and a Master Boiler
will display the Modulation % for the system even though it is
running at ½ of this rate. This method helps protect the heat
exchanger from damage due to excessive delta T’s. If the Master
boiler is running

SEND RETURN

RETURN

RETURN, SYS RET

This setting is used by the Master boiler to select which Return
sensor temperature to send to all Member boilers. The Return
temperature will then be used by the Member boilers (usually non­condensing) to determine if they can be called by the Master to run.

If a System Return sensor is available on the Master, set this setting
to SYS RET. If only a Return sensor is available, set to RETURN.

TEMP DISAB

OFF

SYS RET, RETURN,

OFF

This setting is used by a Member boiler (primarily a non-condensing
type) to determine which return sensor to look at when determining
if it is safe to fire. Its purpose is to keep non-condensing boilers from
firing in a condensing mode.

SYS RET the boiler will use the Return temperature sent from the
MASTER boiler.

RETURN the boiler will use its own Return sensor. If it is set to
OFF, then this feature will not be used.

If a sensor is selected, the Boiler will determine if the Return
sensor’s temperature is below the TEMP< XXX setting. If the Return
temperature is lower, the boiler will take itself offline from the
Master. Informing the Master that it cannot run. The message “blr
offline” will be displayed in the Status screen.

TEMP<140F

140

135F – 200F

Setting determines where the TEMP DISAB return sensor’s

threshold temperature disables the boiler from firing.

DEFAULT SETTINGS & MENU ITEM DESCRIPTIONS HeatNet Control V3

Page 92

DOMESTIC HOT WATER

DHW BOILER?

NO

NO/AUTO, LOCAL,

COMBO

Setting this value to LOCAL or COMBO enables the DHW PID.
Setting this value to NO disables the DHW PID.

LOCAL allows the boiler to run in DHW locally off of its own
sensor or stat input. The boiler could be configured to run as a space
heating boiler that is controlled by a Master. It would also monitor a
tank or DHW call and disconnect from the Master to provide local
DHW heat.

COMBO allows the boiler to be configured to run as a space heating
boiler and a DHW boiler that is controlled by a Master. This method
would use both the space heating PID and the DHW PID to
simultaneously control space heating and DHW heating.

NO turns off the DHW PID, but still allows control of the DHW
pump and DHW setpoint for backwards compatibility.

*Note: If the System is configured to use the OA OVR input to
override the heating setpoint with the DHW setpoint, the DHW PID
is not used. Since this method does not use the DHW PID, the DHW
BOILER setting should be set to NO. The DHW SETPOINT, POST
PURGE, LOCAL PUMP OFF, LOCAL DELAY, and PURGE TO
THE: may need to be set if this method is used. This method does
allow configuring the LOCAL and DHW pumps.

DHW SETPOINT

160 F

40 – 200 F

Setpoint that the boiler/system will target when a call for DHW.

LOWER DHW DIFF

5 F

1 – 30 F

DHW SETPOINT – LOWER DHW DIFF: if the DHW water
temperature is less than this temperature, the Boiler/System will
enter DHW Heating mode if DHW BOILER? Is set to LOCAL or
COMBO.

UPPER DHW DIFF

3F

1 – 30 F

DHW SETPOINT +UPPER DHW DIFF: if the DHW water
temperature is greater than this temperature, the Boiler/System will
begin shutting off DHW boilers if the DHW BOILER? is set to
LOCAL or COMBO

DHW PRIORITY

NO

If the DHW PRIORITY is set to YES, then when there is a call for
DHW, the system pump shuts off. If NO, the system pump stays on.

POST PURGE

120s

0-600 secs

This is the time that the DHW relay remains on after the DHW call
ends.

USE SENSOR?

NO

If this entry is set to YES, the DHW 10k Sensor is looked to for
controlling DHW water temperature. If set to NO, A thermostat is
used.

SHARING

OFF

OFF, NO CYCLE,

CYCLE

NO CYCLE allows the boiler to perform as a space or DHW heating
boiler. DHW always has priority and will override (steal) a space
heating boiler that is running when none are available to perform
DHW heating. When this happens, the boiler will not shut down, but
keep running during the change from space heating to DHW (Hot
Swap). Once the DHW cycle completes, the boiler will shut down
and wait to be called for space heating again.

CYCLE allows the boiler to perform as a space or DHW heating
boiler. DHW always has priority and will override (steal) a space
heating boiler that is running when none are available to perform
DHW heating. When this happens, the boiler will shut down and exit
the space heating mode. The boiler will then re-start as a DHW
heating boiler. Once the DHW cycle completes, the boiler will shut
down and wait to be called for space heating again.

DEFAULT SETTINGS & MENU ITEM DESCRIPTIONS HeatNet Control V3

Page 93

LOCAL PUMP OFF

NO

NO, YES

YES will shut off the local pump/valve when DHW heating is in
effect. If the boiler is running in space heating mode, the LOCAL
DELAY will be in effect before the local pump/valve shuts off.

NO both the local and the DHW pump/valve will be enabled during
DHW heating.

LOCAL DELAY

10 Seconds

0-255 seconds

Seconds is the time in seconds that the local pump/valve will remain
on after the DHW pump/valve is enabled before shutting off. This is
part of the changeover process when the boiler was running in space
heating mode and now needs to provide DHW heating.

This timer may also be used for race conditions when operating
valves. The Local Pump Flow Prove time would be used to prove
flow, but with valves, the local valve may still have flow when the
DHW valve begins to open. This would cause a flow fault when the
local valve closes and the DHW valve still has not opened.

The way it works, is that these timers work in parallel, but this timer
only counts down when flow is present. It stops counting down when
flow stops, but will not cause a flow fault until its time expires. The
Local Pump Flow Prove timer counts down, but normally when flow
occurs, it proves and the boiler is allowed to run. This local delay
timer would then take over instead of allowing the boiler to run, and
wait until its time expires before allowing the boiler to start. This
timer proves that there is flow, whether interrupted or not, for x
(adjustable) seconds. If pumps are used, this value can be set to a few
seconds.

PURGE TO THE

TANK

TANK, SPACE

TANK will keep the DHW pump/valve enabled for the DHW POST
PURGE time thus purging some of the boilers heat into the tank.

SPACE will turn off the DHW pump after 5 seconds and enable the
local pump/valve when a DHW heating cycle completes. This allows
dumping some of the remaining heat from the boiler into the heating
space (dump zone) and preventing the tank from overheating.

HYB SENSOR

OFF

OFF, SUPPLY,

DHW, RETURN

Hybrid mode sensor for DHW method 5A

OFF This sensor is selectable for DHW Method 5A only.

SUPPLY In DHW Method 5A will maintain the DHW setpoint at

the supply sensor when the OR OVR input is closed.

DHW In DHW Method 5A will maintain the DHW setpoint at the
DHW sensor when the OR OVR input is closed. This sensor is
optional and needs to be added. It can be moved around and placed
in the Tank, pipe feeding the tank, or other location to maintain a
setpoint at that location.

RETURN In DHW Method 5A will maintain the DHW setpoint at
the RETURN sensor when the OR OVR input is closed.

SYSTEM CLOCK

TIME

This time needs to be entered at first turn-on and in the event that
power has been lost for more than 3 days. The time is required for an
accurate Night setback, log entry time-stamp, and fault time stamp.

DAY OF WEEK

MONTH

DAY

YEAR

PRESS SEL TO SAVE

The SEL key must be pressed after all time values have been entered
to save all time values at once.

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Default Settings & Menu Item Descriptions — ADVANCED SETUP

DISTRIBUTED CTRL

CONTROL

H-Net

Displays method of operation: HeatNet (H-Net)

H-Net MASTER

YES

Auto detected, based on the HEADER sensor.
If the HEADER sensor is present and is set to TYPEZ, the Futera
III/Fusion-Series control is run as a H-Net MASTER (YES).
If the HEADER sensor is not TYPEZ, H-Net MASTER = NO.

MASTER TYPE

AUTO

AUTO, COMBO,

DHW

Two PID controls are provided, one for Space heating and one for
DHW heating. This menu item selects how they are to be used. The
MASTER TYPE setting is used to determine if the MASTER control
is to be used as a space heating control, a COMBO DHW/space
heating control, or just to perform DHW Heating.

When set to AUTO, the boiler uses one PID control to provide space
heating. When set to COMBO, the control will use two independent
PID controls to provide space heating and DHW heating. When set
to DHW, the control only uses the DHW PID control.

H-NET ADDRESS

255

2 –16

The local address is the address of a Member device. This is
normally in the range of 2 through 16. But if the Futera III/Fusion­Series control is a MASTER, then the default address is 255. The H­NET ADDRESS # is synonymous with boiler #.

MODBUS ADDRESS

1

1 – 247

The MODBUS address is for communicating with Laptop, PC, or
other MODBUS capable device, such as a Building Management
System. It is the 2nd communication port reserved for host control.

MODULAR BOILER SET

SPACE HEATING

DHW HEATING

If the MASTER TYPE is set to COMBO, the MODULAR BOILER
SET is duplicated for each PID. Select SPACE HEATING to set the
ADD, SHED, MODULATE, and MOD MAX values for the space
heating PID. Then select DHW HEATING to set the ADD, SHED,
MODULATE, and MOD MAX values for the DHW heating PID.

ADD BOILER DELAY

10mins

0 – 60min

This is the delay time in 30sec intervals, before starting a new boiler.
Boiler #1 is started immediately after a call for heat. If a second
boiler needs to start, the ADD BOILER DELAY will need to expire
before starting.

SHED BOILER DELAY

2mins

0-15min

This is the delay time in 30 second intervals, before stopping a
boiler. A boiler is stopped immediately when the top of the heat band
is exceeded. If a second boiler needs to stop, the SHEDBOILER
DELAY will need to expire before stopping.

MODULATE DELAY

TIME

10 secs

0 – 60min

This is the time the boiler remains in min-fire before it relinquishes
control to the modulation % signal.

MOD MAX – LAST FIRE

70%

25 – 100%

This value represents the maximum % of input on the boilers if all
the available boilers are not firing. Once all boilers are firing, this
clamp is removed and all boilers are allowed to modulate up to

100%. When this value is limiting the input an ‘*’ is displayed and
the “INPUT CLAMP” message is displayed in the STATUS screen.

This value is derived by: multiplying twice the minimum fire rate of
the boiler with the least turndown (2* turndown (20% 5:1, 25% 4:1,
33% 3:1)).

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In mixed boiler size configurations, more than (2) boilers in a

system, or when “bumps” in the temperature occur as boilers are

added and subtracted, this value may need adjustment. The
adjustments will help produce smooth temperature control when each
boiler is started and stopped. This method ensures that, once a new
boiler starts to fire, and holds its fire rate at the minimum setting, it
does not add its BTU output to a boiler already firing at 100%. The
boilers cannot be fired starting @ 0%, but start at a minimum
(example: 20%) and introduce a minimum amount of BTUs into the
system. Section: SETUP & OPERATION

The MOD MAX value is also applied when using the AA terminal
for High Fire and when using the 4-20 mA input for direct
modulation. When these demands for heat are used, the maximum
modulation the boiler can obtain when first starting is equal to the;
ADVANCED SETUP: MODULAR BOILER SET: MOD MAX –
LAST FIRE:. The timer value ADVANCED SETUP: MODULAR
BOILER SET: ADD BOILER DELAY is used in conjunction to
limit the modulation for this amount of time. Once the boiler has
fired and the ADD BOILER DELAY time expires, the full
modulation is available. This change is a protective means for
extending the life of the heat exchanger which may consistently be
exposed to thermal stress.

ADAPTIVE MOD

MOD MODE

ADAPTIVE

If MODULATION MODE is set to ADAPTIVE on the Master
boiler, the Master lowers the system modulation rate of all currently
running boilers before a newly started boiler enters the Main Valve
state. Upon entering the Main Valve state of a newly fired boiler, the
Master waits the DELAY RELEASE time before allowing the PID to
resume modulation control. With MOD MODE set to ORIG KN,
The Master boiler keeps firing at the current modulation rate when a
new boiler is added and lets the PID adjust modulation rate
accordingly.

DROP DOWN

ON CALL

If drop down is set to ON PILOT and MOD MODE = ADAPTIVE,
and when a newly added boiler starts, the system waits until it enters
its PILOT state before bring the system modulation down. This
allows for the system to prepare for the new energy that is to be
introduced. If DROP DOWN is set to immediately, the system
modulation is lowered as soon as the newly added boiler is called.

DELAY RELEASE

0s

Once the Main Valve opens on the newly added boiler and the MOD
MODE = ADAPTIVE the Master waits this amount of time before
releasing the PID to control modulation. This allows for the newly
added boiler to accumulate some soak time.

This is a global delay controlled by the Master boiler. It is
comparable to the MODULATE DELAY setting, but this is a local
setting on each boiler.

FIRING MODE

MODE

TRUE

LOFO: Boilers are fired Last On, First Off starting with Lead Boiler
FOFO: Boilers are fired First On, First Off
TRUE: Boilers are fired based on the runtime they report back to the
Master boiler. Boilers with the least runtime are fired first and boilers
with the most runtime are stopped first.
MIXED: Different types of boilers can be mixed in a system and
fired based on (2) Priority sets. Boilers are started and stopped with
in the Priority sets based on their runtime hours.

MIN RUNTIME

10

(1-750)

When the firing rotation is based on runtime, this value represents
the interval in hours of runtime before rotation occurs. Boiler to
Boiler.

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MIN OFF TIME

0

0-10m

This is the time in minutes that the boiler must remain OFF before it
can be fired again. Very effective in dynamic systems to minimize
short cycling of a boiler and force the call to the next boiler (with
next shortest runtime if True Runtime is used)

FIRING PRIORITY:

2

1 or 2

There are (2) Priority settings used by the MIXED boiler rotation
algorithm. Priority 2 is the default and lowest priority. Priority 1
Is the highest priority. A Priority may be assigned to a set of boilers
which fires and rotates based on time and is independent of the other
Priority set.

PREDICT START:

YES

YES/NO

YES: Predicts the boiler restart point in the heating band while the
temperature of the boiler is drifting down through the band. The
purpose of this is to ensure the temperature remains in the heating
band. It also minimizes temperature swings when the boiler is
stopped and started at low inputs.

This algorithm looks at the size of the band and at what rate the
temperature is falling. It then calculates when to start the boiler
(knowing its starting time) to ensure the boiler starts within the band.
Once the boiler starts, the Add Boiler Delay time starts and continues
to expire in and below the band. This ensures that another boiler does
not start when it leaves the bottom of the band.

BASE LOADING

BASE LOAD BOILERS:

0

0-1

This setting works in conjunction with the ADVANCED SETUP:
SYSTEM: OPTION setting BASE LOAD. Currently only (1) base
load boiler is supported using relay K8

START

>MOD

START>MOD,
START<OA T,

START>RET

Used in Conjunction with DELAY TIME.

START>MOD

100%

20–100

The base load relay K8 will close when the Modulation is >%.

START<OA T

40–140

The base load relay K8 will close when the OA temp is > T

START>RET

60–150F

The base load relay K8 will close when the Return temp is > T.

STOP

FIRST

FIRST, STOP<MOD,

START>OA T,

START>RET

STOP<MOD

20%

20%20–100

The base load relay K8 will open when the Modulation is <%.

STOP>OA T

40–100 F

The base load relay K8 will open when the OA temp is > T.

STOP<RET

60–150 F

The base load relay K8 will open when the Return temp is < T.

DELAY TIME

0

0–60 minutes

This setting allows a wait time before firing the base load boiler
once the start condition is met.

SENSORS

Sensors can only be changed when there is no call for heat. The boiler must be in STANDBY.

SENSOR #

The first (4) sensor #’s are reserved as: OUTSIDE AIR, water

SUPPLY outlet, water RETURN inlet, and system HEADER
temperature. If the HEADER sensor is used (TYPEZ), that boiler
performs the tasks of the MASTER boiler. If the HEADER sensor is
set to NONE, its function is the MEMBER. The next (3) sensors
perform DHW, Stack, and System Return measurements.

TYPE

There are (4) sensor types:
NONE = do not use this sensor
TYPEZ = 10k thermistor
PT = 1k Platinum (only for Stack temperature)
ON/OFF = 5 volts supplied out to detect a contact/switch closure.

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CALIBRATE

Placing a precision 10k (TYPEZ) precision resistor across the sensor
input selected allows calibration of the sensor input. Do not select
calibrate with the temperature sensing thermistor/PT connected.
Doing this will cause significant temperature errors.

4–20mA INPUT

ANALOG IN CHANNEL:

1

1 -2

There are (2) channels that may be configured for 4-20mA inputs or
0-10VDC inputs. They are labeled 4-20mA (1) and 4-20mA (2). The
4-20mA (1) input is used to direct fire a boiler or to remotely control
the setpoint of the boiler. Analog channel (1) is the primary channel
used for direct modulation and remote setpoint control.

The 4-20mA (2) is a dedicated input used for metered input such as:
Flow meters, etc.

CHANNEL MODE:

4-20mA

4-20mA or 0-10VDC

Type of input to use for the ANALOG IN CHANNEL selected
above. The input may be changed from 4-20mA to 0-10 VDC. The
dip switch S6 also needs to be set correctly in conjunction with this
setting.

4mA SETPOINT

50 F

50-220 F

When using 4-20mA setpoint control in SETPOINTS: SETPOINT
SOURCE. This is the temperature when a 4mA signal is applied and
is tied to the BOILER START mA. The Setpoint will then be
mapped from 4mA –20mA and example default of: 50-220F

20mA SETPOINT

220 F

50-220 F

This is the setpoint temperature when a 20mA or a 10 VDC signal is
applied.

BOILER START

4.11mA

3.71-5.0mA

This is the current value which will start the boiler. There is a .1mA
or .25 VDC hysteresis value. So if the Boiler starts at 4.11mA it
shuts off a 4.01mA.

PRIORITY

NORMAL

If the Priority is set to NORMAL, the boiler responds to its HEAT
DEMAND inputs in the Priority that is outlined in the Control
Methods section. If the PRIORITY is set to HIGHEST, The 4-20mA
input responds at the highest Priority level (same as the AA input).
This method may be used by an external control to override the
HeatNet control and fire the boiler using this external control
(external control override). This allows for complex DHW control
systems where an external control can take over the firing rate for a
DHW call, and direct modulate a boiler. If the PRIORITY is set to
HIGHEST, The 4-20mA input responds at the highest Priority level
(same as the AA input). This method may be used by an external
control to override the HeatNet control and fire the boiler using this
external control (external control override). This allows for complex
DHW control systems.

PASSWORD

AAAAAA

Provides a limited access for security, though restoring system
defaults will reset the password to the value “AAAAAA”

COMMUNICATIONS (Defaults are set for BACnet and LON WORKS communication protocols.)

BAUD

19200

1200, 2400,
4800, 9600,

19200, 38400

This is the Baud rate for serial communication from the MODBUS
port. Selectable from 1200, 2400, 4800, 9600, 19200, 38400.

DATA FORMAT

8E1

8E1, 8N1,

8N2, 8O1

8 bits -Even Parity -1 stop bit, valid settings: 8E1, 8N1, 8N2, 8O1

SETPOINT TIMER

ON

ON, OFF

If set to ‘ON”, the setpoint timer is enabled and requires a periodic
update of its value to keep from timing out and retuning control to
the
H-Net control. If set to “OFF”, MODBUS always has control and on
a loss of MODBUS communications, H-Net does not assume
control.

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SETPT TIME

1 minute

1-240 minutes

This time is used to automatically reset the SETPOINT TIMER
when any Modbus value is written. If it is set to 1 minute, a periodic
write to one of the registers must occur within 1 minute otherwise
the BMS Setpoint will revert back to the System/Local setpoint.

LOAD DEFAULTS

FACTORY CAL?

Selecting YES will load just the factory calibration values:
MINIMUM VFD, MAXIMUM VFD and IGNITION VFD.

FACTORY RESET?

NO

Selecting YES will load all factory defaults except the Calibration
values, HeatNet, and Modbus addresses.

CONFIG ?

SAVES and RESTORES

SETTINGS

SAVE

SAVE/RESTORE

Selecting SAVE will store the setting in the on-board memory in the
event a firmware update is performed, a factory reset needs to be
done, or the settings are changed in error and are unknown.
Selecting RESTORE will reload the saved settings.

FLOWMETER

LOCAL FLOWMETER

NO

YES, NO

If a Local flow meter or flow control is to be used, set to YES

GLYCOL MIX

0%

0-100%

Any mix over 10% de-rates the flow by 30% (rule of thumb
method). Example: if the LOWEST FLOW = 50 GPM, HeatNet will
calculate a New Lowest Flow required to be 65 GPM. The
LOWEST FLOW does not need to be changed, but is calculated to
65 GPM and that value is used by HeatNet.

Flow Prove

GPM

PER BOILER TYPE

Each individual boiler type will have a minimum flow required and
is adjustable within that boilers range.

SYSTEM FLOWMETER

NO

YES, NO

If a System flow meter or flow control is to be used, set to YES

GLYCOL MIX

0%

0-100%

Any mix over 10% de-rates the flow by 30% (rule of thumb
method). Example: if the LOWEST FLOW = 50 GPM, HeatNet will
calculate a New Lowest Flow required to be 65 GPM. The
LOWEST FLOW does not need to be changed, but is calculated to
65 GPM and that value is used by HeatNet.

INPUT TYPE

VOLTS 2

VOLTS (2), mA (2),

BMS,

This setting determines where the flow values are originating. If set
to Volts (2), then a Flow meter is providing a 0-10V signal on J10B
4-20mA (2). Ensure that S6 switch 2 is UP for 0-10VDC.

If the setting is mA (2), then a Flow meter is providing a 4-2omA
signal on J10B 4-20mA (2). Ensure that S6 switch 2 is DOWN for
4-20mA.

If the INPUT TYPE is set to BMS, a Flow Limited or a Boilers
Limited method can be used. With Flow limited a GPM value can
be written to the BMS GPM Modbus register 40019 with a valid
flow. If the Boilers Limited method is to be used, the number of
boilers that the BMS would allow HeatNet to control is written into
Modbus register 40020.

See the Flow Options section for more details.

SET PARAMETERS

LOWEST FLOW

PER BOILER

TYPE

0-500 GPM

This is the automatic value loaded and will equal the lowest flow
required for this boiler (it is adjustable). It should be equal to the
lowest flow of the largest boiler in the system.

HIGHEST FLOW

0

Currently not used.

FULL SCALE

PER FLOW

METER

0-1600 GPM

Enter the value of the full scale reading on the calibration card that
came with the flow meter.

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Flow Factor

PPG

Currently not used.

SYSTEM

BOILER TYPE

CONFIGURE INTERLKS

The 24 VAC interlocks can be enabled or disabled for reporting.

LOAD FIRMWARE

NO

Enters the Load Firmware menu. Loading new firmware allows for
upgrades and bug fixes to the HeatNet control. Check the

http://www.rbiwaterheaters.com/ website periodically for updates.

SOURCE

USB DRIVE

USB DRIVE,

USB CABLE,

SAVE FILE

Selecting USB DRIVE will read the FIRMWARE directory on a
flash drive and display any .hex files located there. Follow the on
screen prompts and then select a file using the arrow keys. Once a
file has been selected, a STORAGE LOCATION needs to be
selected. There are (2) storage locations for the new file. Location 1
is used for normal updates and Location 0 is for the factory stored
backup file. When the Storage location (default is Location 1) is
selected the file will be loaded into a permanent storage memory
location. Next, the control will reboot and copy this new program
into running memory, reboot, load factory defaults, and then reboot
again.

Selecting USB CABLE requires connecting a USB cable and
running the Firmware Update program from a PC. This process
takes longer and requires a Personal Computer (laptop) to be taken
to the boiler site. Again, follow the on screen prompts to down load
the program into a storage location as done when using the above
USB DRIVE loading menu.

Selecting SAVE FILE will display the currently stored files in the
storage memory locations. Use the arrow keys to select a stored file
for copying to running memory. When SELECT is pressed the file
will be marked so it will be loaded on the next power cycle. Power
cycle the boiler to begin copying the file from stored memory to
running memory.

NOTE: to access the factory backup program, the shunt on the

control needs to be connected and the CAL/NORMAL P3 BOOT
switch placed in the CAL position. If the control is power cycled in
this condition, the factory program will overwrite the existing
running program. If in the LOAD FIRMWARE menus, STORAGE
LOCATION 0 will be an allowed storage location. When the
backup program begins to load, remove the shunt on P3 and place
the CAL switch back to normal.

OPTION:

NO OPTION

NO OPTION
DUAL FUEL
BASE LOAD

When set to DUAL FUEL, input T3/ RESERVED, OPTION input
is used to control the DUAL FUEL OPTION relay via K8 contacts
on J4.2 &.6. When set to NO OPTION the input T3/RESERVED,
OPTION relay K8 on J4.2 &.6 is inactive.
When set to BASE LOAD, the Option Relay K8 on J4.2 &.6 is used
as an enable contact for a base load boiler. The J4.1 &.5 0-10vdc/4­20mA output is used to modulate the base load relay if it is of the
modulating type.

BOILER TYPE

PRODUCT:

MB/MW 500

MB/MW 500 ­MB/MW 5000

The product type allows configuration of the control. The following
fields will be adjusted to the default for the product.

CONDENSING

YES

This defines a boiler as condensing or non-condensing. This value is
not used with this version and is displayed only for reference and
future applications.

BTU IN

200,000

This is the BTU input rating of the boiler. This value is not used
with this version and is displayed only for reference.

BLOWER

VFD

VFD

This is the blower type associated with the product. This should not
be changed manually.

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MASS

MEDIUM

LOW,MEDIUM, HIGH

This defines the mass of the boiler. This value is not used with this
version and is displayed only for reference and future applications.

TURNDOWN

5:1

3:1, 4:1, 5:1

This is the turndown of the boiler. For the Futera III/Fusion-Series
the default is 5:1 and determines the minimum firing percentage.
5:1 = Min 20%, 4:1 = Min 25%, 3:1 = Min 33%.
NOTE: The boiler must be set up for operation at this Turndown
rate using the Calibrate settings. This TURNDOWN setting only
controls the displayed percentage.

ALTITUDE

< 2000FT

< 2000 FT,
> 2000 FT,

> 4000 FT

This is the Altitude in feet of where the boiler is installed. On some
Blowers it limits the blower output for low altitudes and allows a
higher output at higher altitudes. Currently, this setting is not used
on the Futera III/Fusion-Series boilers.