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is manual is intended only for use by a qualied 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. e 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 instr uction manual guidelines to clean, repair or replace the boi ler if necessary.

Ax these instructions near to the boiler. Instruct the building owner to retain the instructions for future use by a qualied service technician, and to follow all guidelines in the User’s Information Manual.

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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the like is provided only for your convenience and may be superseded by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, FlexCore CK -

Series, HeatNet, and H-Net 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.

Rights Reserved.

TABLE OF CONTENTS HeatNet Control V3

TABLE OF CONTENTS

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

Introduction .......................................................................................................................................... 6

THE FLEXCORE CK -SERIES V3 HEATNET CONTROL .........................................................................................................................6

Features & Specifications ................................................................................................................... 8

STANDARD FEATURES OVERVIEW .....................................................................................................................................................8

Specifications ..................................................................................................................................... 10

Components & Accessories .............................................................................................................. 11

PART NUMBER .............................................................................................................................................................................. 11

SETUP & OPERATION ....................................................................................................................... 12

BASIC MULTI BOILER SYSTEM OPERATION ....................................................................................................................................... 12

MIXED BOILER TYPES USING PRIORITY SETS ................................................................................................................................... 13

MIXED BOILER SYSTEM OPERATION ................................................................................................................................................ 14

START/STOP PRIORITY CONDITIONS ............................................................................................................................................... 16

SELECTING MIXED BOILERS ........................................................................................................................................................... 17

MIXED SYSTEM TYPE 1: HIGH SYSTEM TURNDOWN ......................................................................................................................... 17

MIXED SYSTEM TYPE 2: CONDENSING/NON-CONDENSING ................................................................................................................. 20

Heating Control Methods ................................................................................................................... 24

HEATING METHOD 1 ...................................................................................................................................................................... 24

HEATING METHOD 2 ...................................................................................................................................................................... 24

HEATING METHOD 3 ...................................................................................................................................................................... 24

HEATING METHOD 4 ...................................................................................................................................................................... 24

HEATING METHOD 5 ...................................................................................................................................................................... 24

OPERATING LIMIT .......................................................................................................................................................................... 24

INPUT PRIORITIES .......................................................................................................................................................................... 25

HEATING METHOD 1 HEAT DEMAND ................................................................................................................................ ............ 25

HEATING METHOD 2 STAGE CONTROL T1-T2 ................................................................................................................................ 26

HEATING METHOD 3 4-20 MA CONTROL .......................................................................................................................................... 26

HEATING METHOD 4 AA INPUT........................................................................................................................................................ 27

HEATING METHOD 5 MODBUS COMMUNICATIONS ........................................................................................................................... 27

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

DHW METHOD 1: DHW HEATING ONLY USING A DHW MASTER AND MEMBER BOILER(S) EMPLOYING H-NET .................................... 29

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

VALVES (MASTER TYPE: COMBINATION) ......................................................................................................................................... 33

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

(MASTER TYPE: COMBINATION) ..................................................................................................................................................... 35

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 ......................................................................................................................... 55

Page 3

DHW MAXIMUM RUNTIME .............................................................................................................................................................. 55

BASE LOADING, RELAY CONTROL ................................................................................................................................................... 56

Using the 4-20 mA input (OPTIONAL) ............................................................................................... 59

SETPOINT PRIORITIES ................................................................................................ .................................................................... 60

Circulator Pump Options ................................................................................................................... 60

Local Pump Options ........................................................................................................................... 62

Combustion Air Damper .................................................................................................................... 63

Outdoor Reset..................................................................................................................................... 63

Sensors ............................................................................................................................................... 64

Stack Temperature ............................................................................................................................. 64

Security ............................................................................................................................................... 64

Save/Restore Configuration Settings ................................................................................................ 64

USB Features ...................................................................................................................................... 64

Diagnostics ......................................................................................................................................... 65

Blower Protection ............................................................................................................................... 65

Communications ................................................................................................................................ 66

Failsafe Modes ................................................................................................................................ .... 66

FAILSAFE REQUIREMENTS: .................................................................................................................................................... 66

Limited Flow Boiler Control Options ................................................................................................. 67

FlexCore Multi Heat Exchangers ....................................................................................................... 69

(3) HEAT EXCHANGER WIRING ........................................................................................................................................................ 71

HeatNet Online ................................................................................................................................ .... 72

Wiring Connections ............................................................................................................................ 73

Home Screen Navigation ................................................................................................................... 85

Home Screen ...................................................................................................................................... 86

Home Screen Messages ..................................................................................................................... 87

HEATING MODE MESSAGES: ........................................................................................................................................................... 87

SETPOINT SOURCE MESSAGES ....................................................................................................................................................... 88

GENERAL MESSAGES: ................................................................................................................................................................... 88

Calibration ........................................................................................................................................... 95

CALIBRATION WITH MULTIPLE HEAT EXCHANGERS ............................................................................................................................ 96

Log Entry ............................................................................................................................................. 97

CONTROL SETTINGS MENU .............................................................................................................. 98

CONTROL SETTINGS MENU— PAGE 1 ............................................................................................ 99

CONTROL SETTINGS MENU— PAGE 2 .......................................................................................... 107

CONTROL SETTINGS MENU — PAGE 3 ......................................................................................... 115

Page 4

TABLE OF CONTENTS HeatNet Control V3

CONTROL SETTINGS MENU — PAGE 4 ......................................................................................... 117

MODBUS Communications ............................................................................................................. 118

Worksheet ......................................................................................................................................... 129

Type II Thermistor Resistance/Temperature Table ........................................................................ 134

Page 5

FEATURES & SPECIFICATIONS HeatNet Control V3

SETPOINT

UPPER HEAT

BAND LIMIT

LOWER HEAT

BAND LIMIT

Boilers Staged

BOILERS

STAGED

OFF

Time

WATER

TEMPERATURE

target setpoint. This function is displayed in the Home

Introduction

Screen. 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

The FlexCore CK-Series V3 HeatNet Control

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

With the FlexCore CK -Series, optimized heating efficiency is accomplished by setting the Modulation Maximum (ModMax) 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

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 FlexCore CK-Series boiler employing this control can function as either a Master or a member. This allows one boiler (Master) to be in control of 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 members. 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.

efficiency of the FlexCore CK -Series boilers.

The Master senses and controls the common system The FlexCore CK -Series boiler with the FlexCore CK Series H-Net control, can be operated in multiple ways:

1. As a stand-alone boiler.

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

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.

(H-Net®) protocol.

3. A member boiler to a boiler management system with

multiple input control methods.

When operating as a Master, the boiler provides a control

method using a PID algorithm to regulate water

temperature. This algorithm allows for a single boiler

(Master), or multiple (Master + Member) boilers.

Home Screen

The primary purpose of the control is to maintain the boiler water temperature at the supply or the header sensor using a

Page 6

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

Features and Specifications HeatNet Control V3

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 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.

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 stand-alone 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.

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:

In a stand-alone 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 stand-alone 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 4-20 mA signal along with a 4-20 mA enable signal to control the firing rate or setpoint. The boiler may also be treated as a 2-stage boiler or an ON-OFF boiler using the dedicated T-inputs.

Page 7

FEATURES & SPECIFICATIONS HeatNet Control V3

Features & Specifications

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

1. Support for (2) Circulator pumps. 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 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.

7. System Return sensor input.

8. Enhanced bootloader 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.

17. 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 4-20 mA 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 4-20 mA 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 FlexCore

CK -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.

9. Automatically detects the optional temperature sensors

on power up.

10. Menu driven calibration and setup menus with a bright

(Adj.) 4 line Vacuum Fluorescent Display.

9. Support for High Efficiency Ametek blowers.

10. 32 bit Microcontroller operating @ 64 MHz with

5-stage pipeline, and prefetch cache.

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

12. Backwards compatible with existing HeatNet versions

1.x and 2.x controls and applications.

13. Support for 135 Ohm control actuators.

14. 1k Platinum Stack sensor

15. Flow meter input or BMS GPM input/control

16. On-board HeatNet Online network module.

Page 8

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.

FEATURES & SPECIFICATIONS HeatNet Control V3

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 4-20 mA setpoint control using a mapped

setpoint range to the 4-20 mA 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.

FlexCore Multi Heat Exchangers

1. Multiple HeatNet controls serving each heat exchanger.

2. Direct wiring for Heat Exchanger - HeatNet to HeatNet

handshaking.

3. New Minibus for digital communication between

internal HeatNet boards.

4. Personality profiles for each FlexCore model.

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. Delayed Blower Power staging. Used to minimize inrush currents by powering the blower 7 seconds after main power.

37. Domestic Hot Water time out for maximum DHW runtime.

38. Added the Local Minibus for inter-boiler communication. Primarily FlexCore series.

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 System Pump, Damper, Circulator, Alarm, DHW Pump (v2.x), 8A 250 VAC resistive

K8 on J4.2 &.6 for Base Loading version 2.x Control

AC Interlocks 24 VAC – 120 VAC input

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

4-20 mA, 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)

Heat Exchanger to HeatNet (Minibus) Heat Exchanger

Network Optional LonWorks, BACnet available bridge to MODBUS port

Page 10

Components & Accessories

Part Number

40-0092 FlexCore CK -Series Control Board Version 3.x Full version (Manager)

40-0093 FlexCore CK -Series Control Board Version 3.x Lite Version (Subordinate)

40-0090 Color Touch Panel Display (CK1500 – CK3000)

40-0091 Color Touch Panel Display (CK3500-CK9000)

16-0026 ACI/10K-CP-BP Temperature probe (bullet type, 1x.250 inch)

14-0325 ACI 10k-CP-I-NW Supply, Header, Return Sensors

13-0104 ACI CP-I-2.5” Sensor with well

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

14-0319 ACI 10k-CP-O Outside Air Sensor with Housing

82-0403 Installation & Operation Manual

44-0060 RJ45 Communications Cable Assembly, 25 feet

40-0115 Ribbon Cable Assembly (Display Control)

44-0061 USB Cable Assembly, 6ft

Contact Factory MODBUS to BACnet bridge

Contact Factory MODBUS to LonWorks bridge

Contact Factory MODBUS to HeatNet Online bridge

Page 11

SETUP & OPERATION

1 to 16 Boilers

Member BoilersMaster

SETUP & OPERATION

Basic Multi Boiler System Operation

For boiler system setup/installations

please 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 amongst all of the boilers.

The Version 1.6 HeatNet board requires Minibus connections for FlexCore boilers with more than (1) heat exchanger. The Minibus requires a serial data cable between each HeatNet Control board. The first and last Heat Exchanger must have the minibus terminated for the bus to work properly. S1 would be placed in the ON position as indicated below for the front and rear heat exchangers. The jumper, JS1 must always be in the position indicated (closest to S1). It is used for testing.

(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 using 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 SETTINGS: 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 designated 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.

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

When a boiler receives a command to fire:

NOTE: Runtime messages are displayed in the lower left corner of the Home Screen. See Section Messages for descriptions.

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

control displays “Waiting for Flow” until the flowswitch closes between J11A, 1 & 2 within the programmed time (10 seconds default).

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 “Waiting for Damper to Open” until the damper end switch closes.

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

used). The H-Net control commences its Waiting for

Page 12

SETUP & OPERATION HeatNet Control V3

Flow” 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. The control now displays “Waiting for Start Sequence”

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. If an Ametek blower is used, a soft start speed is applied before the 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 “Running 0%” (0% indicates PID modulation signal is not being calculated yet).

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

SETTINGS: ADAPTIVE MODULATION 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 FLEXCORE CK-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 stand-alone 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.

Page 13

SETUP & OPERATION

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: (SETTINGS: FIRING MODE: FIRING PRIORITY: PRIORITY: 1). If the Start condition for the Priority 1 set is met (SETTINGS: FIRING MODE: MIXED BOILERS 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 available. The Master boiler then looks at which boilers are returning Priority firing status (set on a boiler in: (SETTINGS:FIRING MODE: MIXED BOILERS LAST(example) If the Stop condition for Priority 1 is met, the Master or Member boiler that are 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 the remaining PRIORITY 1 set of boilers, will stop based on runtime. If the Stop condition changes and/or is not met (such as with: OA T 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: SETTINGS: FIRING MODE: FIRING PRIORITY: PRIORITY menu on each boiler. A Priority of ‘1’ is the highest priority, a ‘2’ the lowest (default is always 2).

Page 14

SETUP & OPERATION HeatNet Control V3

Mixed Boilers: Example: Condensing/Non-Condensing

Page 15

CONTROL METHODS HeatNet Control V3

In the example Mixed Boilers: Condensing/Non- Condensing, 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. SETTINGS: FIRING MODE: MIXED. Pressing the MIXED BOILERS tab 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.

2. The Return water temperature is below 140F and

condensing occurs. (The Master’s system return water would need to be used.)

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.

Once the Mixed Boilers 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.

Note: 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. See: SETTINGS: HEAT EXCHANGER TEMP DISAB:

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. 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

Page 16

Selections (always the highest runtime first):

CONTROL METHODS HeatNet Control V3

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 be applicable in most configurations since the local return temperature on the Master is used to provide a delta 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 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 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 OA T < 15F (Outside Air Temperature) condition. This setting may be used to stop the Priority 1 boiler set when the OAT drops below the OA T setpoint, thus leaving the large base loaded boiler on and shutting off the condensing boilers first. This is also true when using the OA T setting to start the Priority 1 boiler set when the OA T 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 in.

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.

Page 17

CONTROL METHODS HeatNet Control V3

System

MMBTU

Effective

Turndown

MOD MAX

CK 5:1

24.0

20:1

70%

6000, 6000, 6000,

6000

12.0

20:1

70%

3000, 3000, 3000,

3000

20:1

70%

1500, 1500, 1500,

1500

System

MMBTU

Effective

Turndown

MOD

MAX

Priority 1

CK 5:1

Priority 2

CK 5:1

8.0

26:1

45%

1500, 1500

2500, 2500,

9.0

30:1

50%

1500, 1500

3000, 3000

9.5

30:1

50%

2500 2500

5000,5000

Series

1500

2000

2500

3000

3500

4000

Max

Input

1500

2000

2500

3000

3500

4000

Min

Input

300

400

500

600

700

800

5:01

Mod Max

1200

1600

2000

2400

2800

3200

80%

Mod Max

1050

1400

1750

2100

2450

2800

70%

Mod Max

900

1200

1500

1800

2100

2400

60%

Mod Max

750

1000

1250

1500

1750

2000

50%

Series

4500

5000

6000

7000

8000

9000

Max

Input

4500

5000

6000

7000

8000

9000

Min

Input

900

1000

1200

1400

1600

1800

5:1

Mod Max

3600

4000

4800

5600

6400

7200

80%

Mod Max

3150

3500

4200

4900

5600

6300

70%

Mod Max

2700

3000

3600

4200

4800

5400

60%

Mod Max

2250

2500

3000

3500

4000

4500

50%

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 CK Series/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:

Non-Mixed Boiler System Examples

CK Series 1500 – 4000 Modulation Parameters

CK Series 4500- 9000 Modulation Parameters

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 * 5:1 = 25:1.

Mixed Boiler System Examples

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.

When selecting the Priority 1 boiler(s) for a high effective system turndown, the BTU Min Input is selected first. (See: CK/Futera III/Fusion Boiler Btu Chart). Next, the MODMAX 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

Page 18

CONTROL METHODS HeatNet Control V3

The reason for this is to keep the continuity of BTUs linear without a BTU bump (discontinuity) when boilers are added or shed. The Mod Max % can be adjusted to the high side to allow for tolerance (about 10%) as is indicated in the tables. 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) CK 1500, (2) CK 2500 Redundancy: (300 + 500)/1500 = 53% No Redundancy: (300 * 2) + 500) / (1500*2) =36%

In this example, if “Redundancy” is used, the variable “# of Priority 1’s” is not used.

EXCEPTION NOTES:

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.

Typical Efficiency of Non-Condensing Boilers

Typical efficiency of Flexcore boilers

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.

In the Mixed Boiler System table line 1 example, (2) CK 1500s are set as Priority 1 and (2) CK 2500 boilers are set as Priority 2. With a MOD MAX of 50% (Redundancy), each 1500 can run to 750M (1500M total) before a 2500 is called ON (Add Delay timer). Once both 1500s are running and the 2500 is called on, all (3) boilers will drop to a sum of 1500M BTUs: Taking this1500M value and dividing by total M BTUS of the (3) boilers, 1500 +1500+1750 = 5500, we get 27.27%. (.2727* 1500M) + (.2727* 1500M) + (.2727* 2500M) or: 409M +409M + 681M = ~1500M and operate at higher combustion efficiencies

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

Page 19

CONTROL METHODS HeatNet Control V3

0.00

0.10

0.20

0.30

0.40

0.50

0.60

0.70

0.80

0.90

1.00

0 1,500,000

2,750,000

4,000,000

5,000,000

6,000,000

, %

System Load, Btu/Hr

Blr1 (750 MBTU)

Blr1+Blr2+Blr3 (2750 MBTU)

Blr1+Blr2+Blr3+Blr4 (4000 MBTU)

Blr1+Blr2 (1500 MBTU)

8,000,000

0.00

0.10

0.20

0.30

0.40

0.50

0.60

0.70

0.80

0.90

1.00

0 2,000,000

3,250,000

5,000,000

7,000,000

9,000,000

I n p t %

System Load, Btu/Hr

Blr 1+2 (2000 MBTU)

Blr 1+2+3 (9000 MBTU)

Blr 1+2+3 (3250 MBTU) Blr 1 (750 MBTU)

750,000

Boiler System Response 1

(2) CK 1500s, (2) CK 2500’s

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 50%, 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) CK 1500 (one of the CK 1500s was taken offline) were used with (2) CK 2500’s and the Mod-Max is set to 50%, the CK 1500 would fire to 750 MBTUs and wait for the CK2500 (Boiler System Response 2 graph). Now, the minimum input rate would be 500M (CK 2500) + the 300M (CK 1500) (already running, but dropped to low fire, but it needs to go to 18.75%, when the CK 2500 starts), the total being 800M. The turndown limits the boiler to running at a minimum of 20%. With a 50% MOD-MAX clamp, there would be 50 MBTUS more than needed that would be added to the system when the CK 2500 fired.

The PID algorithm would then compensate for the discontinuity (bump) in BTUs and the CK2500 would short cycle. To compensate for this, the Mod Max percent would need to be increased by 3%, but should be increased by at least 5% to 55% to allow tolerance. 10% is a better tolerance choice if room is available. This allows the load to fluctuate without causing short cycles.

1500 * .55 = 825 MBTUS.

This new Mod-Max value will allow the sum of the low fire BTUs of both boilers to fire at; 300 + 500 = 800 MBTUs with room of 25 MBTUs, and prevent the short cycle condition.

Boiler System Response 2

(1) CK 1500, (3) CK 2500, 50% Mod-Max

While a CK 1500 running with a CK 2500 is an acceptable solution, it may not be an optimal choice unless (2) CK 1500s are used in the Priority 1 set and one is allowed to be taken offline (for Redundancy).

A system employing this redundancy where (1) is allowed to be taken offline is listed in the MIXED BOILER SYSTEM chart. This system uses (2) CK 1500s and (2) CK 2500s. Two of the CK 1500s are treated as one when adding the min inputs of the Priority 1 set.

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

In the following examples, condensing boilers will be used with non-condensing mass boilers. The reason for creating a mixed system is primarily to control the system cost.

Note: In a mixed condensing/non-condensing system, boilers with differing sizes, as outlined in the Mixed System Type 1: High System Turndown section may also be used.

Page 20

CONTROL METHODS HeatNet Control V3

Local Pump

MASTER

Condensing

MEMBER 1

Condensing

HNETHNET

Header Sensor

System Return Sensor

HNET

Local Pump

System Pump

MEMBER 2

Non-

Condensing

MEMBER 3

Non-

Condensing

Priority 1 Set Priority 2 Set

Combustion Air Damper

Outdoor Air Sensor

Outdoor Air

Sensor

System

MMBTU

Effective

Turndown

MOD

MAX

Priority 1

CK 5:1

Priority 2

MB/MW

7.5

25:1

55%

1500,

1500

4:1

1500, 1500,

1500

10.5

35:1

60%

1500,

1500

5:1

2500, 2500,

2500

30:1

55%

3000,

3000

5:1

4000, 4000,

4000

26:1

55%

4500,4500

5:1

5000, 5000,

5000

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

MB/MW

2500

3000

3500

4000

5000

Max Input

2500

3000

3500

4000

5000

Min

5:1

500

600

700

800

1000

Mod Max

80%

2000

2400

2800

3200

4000

Mod Max

70%

1750

2100

2450

2800

3500

Mod Max

60%

300

450

600

750

900

Mod Max

50%

1250

1500

1750

2000

2500

Mixed Condensing/Non-Condensing Boiler

System

Note: 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.

Futera III/Fusion/ Boiler Btu Chart (MBH)

Futera XLF Boilers

Mixed Boiler System Examples

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.

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, at lower firing rates, 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.

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.

Page 21

CONTROL METHODS HeatNet Control V3

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 (Condensing) will be set to 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 (non-condensing). 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.

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.

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.

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

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

NOTE:

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 EXCHANGER: 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 EXCHANGER: TEMP DISAB: SYS RET needs to be set. Then the Master boiler needs to set SETUP: AUX FUNTIONS: HEAT EXCHANGER: 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 EXCHANGER: TEMP DISAB:” if set to RETURN or SYS RET, will force the boiler to become unavailable to HeatNet when the SETUP: AUX FUNCTIONS: HEAT EXCHANGER: 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

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

This is the 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.

Page 22

CONTROL METHODS HeatNet Control V3

0.00

0.10

0.20

0.30

0.40

0.50

0.60

0.70

0.80

0.90

1.00

0 3,300,000

4,800,000

6,000,000

8,000,000

10,500,000

System Load, Btu/Hr

Blr 1+2+3 (3300 MBTU)

Blr 1+2+3+4 (4800 MBTU)

Blr 1+2+3+4+5 (10500 MBTU)

900,000

Blr 1 (900 MBTU)

Blr 1+2 (1800 MBTU)

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.

In a mixed condensing/non-condensing boiler system example: (2) CK 1500s are set as Priority 1 and (3) MB/MW 2500s are set as Priority 2. With a MOD MAX of 60%, each CK 1500 can run to 900M (1800M total) before a MB/MW 2500 is called ON (Add Delay timer). Once both CK 1500s are running and the CK 2500 is called on, all (3) boilers will drop to a total of the 1800M BTUs. Taking this 1800M value and dividing by total M BTUS of the (3) boilers The sum of the CK 1500, CK 1500, and CK 2500 would equal about 32.7% modulation: (.327* 1500M) + (.327* 1500M) + (.327* 2500M) or: 490.5M +490.5M +

817.5M =~ 1800M and operate at higher combustion

efficiencies: 32.7% is roughly between the top two lines on the Typical Efficiency of Condensing Boilers chart.

The 5:1 turndown of the boilers can allow the Mod Max clamp to go lower, but return water temperatures need to be

taken into account to ensure the Priority 2 boilers don’t

enter a condensing state. Each system is different and adjustments to the Mod Max value can be adjusted to achieve the greatest efficiency.

So, for the first 1800 MBTU of load, the combustion efficiency is maximized by running the (2) CK Series boilers from low to middle input rates. Running the (2) CK 1500 boilers first, also has the added effect of minimizing the return water temperatures of <140F from reaching the non-condensing boilers.

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.

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%.

Boiler System Response 5

(2) CK 1500s, (3) MB/MW 2500s

Page 23

CONTROL METHODS HeatNet Control V3

MASTER

System Header Sensor

System Return

Sensor

Local Pump

System Pump

Expansion Tank

Backflow

Prevention

Pressure

Reducing

Ball Valve

System Pump

Supply Header Se nsor

HeatNet

Outdoor Air Sensor

MIN 3X PIPE DIAME TERS

MAX 10X PIPE DIAME TERS

BETWEEN CENTERS

Water Meter

System Supply

System Return Sensor

Heating Control Methods

An overview of the (5) methods for controlling the FlexCore CK -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 FlexCore CK -Series boiler in its stand-alone 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.

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.

Basic Single Boiler

Heating Method 3

The third method is to allow a remote 4-20 mA or 0-10 VDC signal to control the firing rate (modulation) of the boiler using the 4-20 mA input, along with the 4-20 mA 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 raise 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).

requirements and safe operation.

Heating Method 2

The second method is to view the FlexCore CK -Series boiler as two separate boilers or as a HIGH/LOW boiler using T1 & T2.

Page 24

Operating Limit

When the Master boiler or an external control input is used to control a member boiler (i.e. AA, T1-T2, 4-20 mA, 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 SETTINGS: SETPOINTS: OPERATE 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.

CONTROL METHODS HeatNet Control V3

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

run at System setpoint.

Local Pump

MASTER

MEMBER

HNETHNET

Space Heating

Loop

Header Sensor

MEMBER

System Return Sensor

HNET

Local Pump

System Pump

Input Priorities

The FlexCore CK-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 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. The 4-20 mA input may be raised to this Priority using SETTINGS: 4-20 mA INPUT: PRIORITY.

Priority 2

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

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

Heat demand input

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)

Priority 4

The 4-20 mA/0-10VDC input in tandem with the 4-20 mA REMOTE ENABLE input is next. Any signal over 4.02 mA 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 supply 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.

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.

HeatNet Boilers Configured as Reverse Return

Page 25

CONTROL METHODS HeatNet Control V3

Method 2

Stage Control Inputs:

T1 & T2

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: SETTINGS: 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. The 4-20 mA setpoint control function works in

conjunction with this mode. This function translates a 4-20 mA control signal to a setpoint mapped between 50F and 220F. These (2) temperatures are adjustable to provide a setpoint range. The minimum start current is also adjustable between 3.71 and 5 mA. The setpoint control feature is used in conjunction with the REMOTE ENABLE input on J12A. This feature is enabled in the SETPOINTS menu as: SETPT SOURCE 4-20 mA

Stage control input

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 4-20 mA input will all override the stage control inputs.

Heating Method 3 4-20 mA Control

4. 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.

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

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

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

A 20 mA signal will fire the boiler at the maximum firing rate. The input current signal is viewed as a percentage to the boiler from 0 to 100% (0-20 mA). This means that a 20% (4mA) input signal is required to start the boiler, but since the boiler is classified as having example: 4:1 turn down ratio, the boiler can only be fired as low as 25% of output. Any signal between 20% and 25 %, will fire the boiler at the minimum fire rate. If the MINIMUM setting of the boiler is set above the example: 4:1 turndown of 25% (such as 33%), a control signal change between 25% and 33% will not change the boilers firing rate. Once the control signal rises above the MINIMUM fire rate, the control signal will then affect control of the boilers fire rate.

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

Page 26

CONTROL METHODS HeatNet Control V3

Modbus Using

RJ45 Cat 5 cable

Modbus Using

shielded 3 wire.

Building

Management

Method 4: Close this AA contact

to run the boiler at High Fire.

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

Heating Method 5 MODBUS communications

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 SETTINGS: COMMUNICATIONS: SETPOINT TIMER: OFF. If the setpoint timer feature is set to ON, the SETTINGS: COMMUNICATIONS: SETPOINT TIMER 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.

Protocessor option

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

Protocessor bridge module option

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.

MODBUS connections

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.

Page 27

CONTROL METHODS HeatNet Control V3

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 41 for control input and Figure 49 for output locations.

Jumper JPS1

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

DHW: is for DHW applications without space heating.

Combination: 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 (BOILER MODE? OFF). 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 Combination the

MODULAR BOILER menu will contain (2) separate menu tabs for controlling the ADD BOILER DELAY, SHED BOILER DELAY, MODULATE DELAY, and the MOD MAX for the SPACE HEATING and DHW HEATING. This allows the independent control of boilers by the Master for each of the (2) PIDs.

Note: 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 CONTROL menu. Any time its setting is changed, a power cycle is required. The menu choices are:

Page 28

CONTROL METHODS HeatNet Control V3

MASTER

MEMBER 2

MEMBER 3

HNETHNET

Tank Sensor

DHW Sensor

Ball Valve

Expansion T ank

Pressure

Reducing

Cold Wate r

Makeup

Backflow

Prevention

Local Pump

Domestic

Supply

Domestic

Supply

Water Met er

HeatNet

Local Pump

HeatNet

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

Example DHW Only, Reverse Return Piping – Method 1.

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.

Page 29

CONTROL METHODS HeatNet Control V3

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

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

Off

Inputs

Local/Remote

JPS1 Jumper must be cut to service DHW

Remote

Outputs

Local Pump On

When Boiler Running

DHW Method 1 Quick Start Settings

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

Note: 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.

Page 30

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RBI CK 3500, CK 1500, CK 1000, CK 4000, CK 4500 Control Manual

Specifications and Main Features

Frequently Asked Questions

User Manual