Honeywell AQ251 Series Product Information Sheet

PRODUCT DATA

69-1974-07

AQ251 Series

Boiler Reset Control Panels

PRODUCT DESCRIPTION

The AQ251 Series of AQUATROL® Boiler Reset Controls

provides simplified, energy-efficient outdoor temperature

compensated control of a high-temperature boiler loop in

residential hydronic heating systems. The AQ251 easily

converts a single-zone heating system into a room-by-room

comfort control system. The boiler controls of the AQ251 can

ensure ample supply of hot water for both space heating and

priority generation of domestic hot water for bathing, dishes

and laundry.

FEATURES

The AQ251 Series has the following features:

• Outdoor temperature compensation (reset), or Load

reset based on indoor temperature feedback, or none

• Domestic hot water (DHW) priority and priority

override protection.

• Customizable control settings and schedules allow for

greater level of control and comfort.

• Central set-back schedules available.

• Zoning Control for up to four, single-stage zones or

two, two-stage zones as shipped; can be expanded to

a total of 16 zones with AQ255 or AQ257 expansion

zoning panels, and up to 64 zones by using up to three

AQ254 Add-a-Temperature expansion panels and

additional expansion zoning modules.

• Use with digital non-communicating thermostats or

AQ1000 2-wire polarity insensitive communicating

thermostats.

• When using non-communicating thermostats, the

following features are not available:

• Outdoor temperature is not displayed on the

thermostat.

• Time clock on AQ1000TP2 will not synchronize

with the Control Module.

• Central programming, vacancy and setback

schedules of AQ1000 from AQ panel are not

enabled.

• AQ panel will not display individual zone

temperatures.

• Individual zone freeze protection.

• Allows display of outdoor temperature on all AQ1000

thermostats when used with an AQ12C10 outdoor

sensor (included).

• Intuitive programming interface (can be programmed at

your shop and taken to the job site “ready-to-install”).

• Pump/valve exercise.

• Line or low-voltage output for zoning equipment

(pumps or valves).

• Integral 38 VA transformer with self resetting electronic

fuse.

• Automated test and purge feature for quick start-up

and simplified troubleshooting.

• Two hour power supply module (super capacitor)

retains day and time settings during power outage and

a non-volatile EPROM memory retains program

settings during power outage.

Contents

Specifications ................................................................... 2

1 Installation Preparation .................................................. 3

2 Mounting ........................................................................ 5

3 Wiring Procedure .......................................................... 6

4 Program and Configure the Control Panel .................... 14

5 Test and Check Out the Installation ............................... 18

6 Purge Air from all System and Zone Piping .................. 19

7 Document and Keep a record of all System Settings .... 19

Troubleshooting ................................................................ 20

Appendix .......................................................................... 23

User Menu ........................................................................ 23

Installer Menu ................................................................... 30

AQ251 SERIES BOILER RESET CONTROL PANELS

69-1974—07 2

ORDERING INFORMATION

When purchasing replacement and modernization products from your TRADELINE® wholesaler or distributor, refer to the

TRADELINE® Catalog or price sheets for complete ordering number. If you have additional questions, need further information,

or would like to comment on our products or services, please write or phone:

1. Your local Honeywell Environmental and Combustion Controls Sales Office (check white pages of your phone directory).

2. Honeywell Customer Care

1885 Douglas Drive North

Minneapolis, Minnesota 55422-4386

3. http://customer.honeywell.com or http://customer.honeywell.ca

International Sales and Service Offices in all principal cities of the world. Manufacturing in Belgium, Canada, China, Czech

Republic, Germany, Hungary, Italy, Mexico, Netherlands, United Kingdom, and United States.

SPECIFICATIONS

The AQ251 Control Panels and corresponding attached

equipment are listed in Table 1.

Table 1. AQ251 Series Control Panel Models.

Application: Controls one boiler, as well as domestic hot

water (DHW) management and zoning operation in a

hydronic zoning system.

Power and Electrical Ratings:

Power Supply: 120 Vac / 60Hz

Auxiliary Pump Contact Rating: 120 to 240 Vac, 5A, 1/3

Auxiliary Low Voltage Contact Rating: 24 Vac, 0.5A,

12VA

Boiler (T-T) Contact Rating: 24 Vac, 0.5A, 12VA

Boiler Pump (C1-C2) Output Rating: 120 Vac 5A, 1/3HP

DHW Pump/Valve Output Rating: 120 Vac 5A, 1/3HP

B–B Communication Bus Terminals: Low voltage,

Class II, 2-wire polarity-insensitive, digital

communicating link to other Control or Zoning modules

Electrical Connections (Line Voltage): Wire-clamp

screw terminals; maximum 2 x 14 AWG each on line

voltage terminals

Environmental Ratings:

Control and Zoning Panel Temperature Rating: 32°F to

130°F (0°C to 55°C)

Operating Humidity Range (% RH): 5 to 90% RH, non-

condensing

Temperature Ratings:

Boiler Design Temperature: 80°F to 210°F (26°C to

99°C)

Boiler Differential: 2°F to 41°F (1°C to 23°C), or Auto

Boiler High Limit Control Temperature: OFF, 120°F to

225°F (OFF, 49°C to 107°C)

Boiler Low Limit Control Temperature: OFF, 60°F to

180°F (OFF, 15°C to 82°C)

Outdoor Low Design Control Temperature: -60°F to

32°F (-51°C to 0°C)

Boiler Minimum Return Control Temperature: OFF,

80°F to 180°F (OFF, 27°C to 82°C)

Sensor Temperature Rating: -58°F to 230°F (-50°C to

110°C)

Warm Weather Shut Down (WWSD) Temperature:

OFF, 35°F to 100°F (OFF, 1°C to 38°C)

Cold Weather Shut Down (CWSD) Temperature: OFF,

32°F to 100°F (OFF, 0°C to 38°C)

Inputs/Outputs:

Auxiliary (Demand) Input: External dry contacts

connection only

DHW Demand Input: External dry contacts connection

only

R–C Input (on Control and Zoning Modules): 24 Vac

Class II

R–C Output (on transformer): 38 VA, 24 Vac Class II

Heat Demand Input External dry contacts connection

only

Modulating Output: 0-10 or 2-10 Vdc for variable speed

pump or modulating boiler

Mixing Valve Output (floating, open/close) (dry relay):

24 Vac, 12 VA

Interface and Timings:

User Interface (Setting, Programming): LCD Display

and a 7-button keypad

Setback Program: 7 day, up to 2 setback periods/day.

DHW Valve Open: 0-230 seconds, before boiler loop

pump is energized.

DHW Purge: Yes/No; selects whether purge is applied

after a DHW demand is served

Boiler Heat Post Purge:

Off, 10 seconds to 30 minutes

(factory default is 30 seconds)

Pump/Valve exercise: 30 seconds per 2 weeks of space

heating inactivity

Thermostat Compatibility: Digital thermostats and/or

AQ1000 Series 2-wire communicating thermostats

Supply/Return Loop Sensor: 10K ohm NTC thermistor at

77°F (25°C) ± 0.5°F (±0.3°C). Lead length: 10 ft. (3.0 m);

up to 500 ft. (150 m) using 18 AWG or larger wire,

beta=3892.

Control Panel

Corresponding

Control Module

Corresponding

Zoning Module

AQ25110B AQ15100B none

AQ25142B AQ15100B AQ15540B

AQ25144B AQ15100B AQ15740B

AQ251 SERIES BOILER RESET CONTROL PANELS

3 69-1974—07

Outdoor Sensor: 10K ohm NTC thermistor at 77°F (25°C) ±

0.5°F (±0.3°C). Lead length: 15 ft. (4.6 m); up to 500 ft. (150

m) using 18 AWG or larger wire, beta=3892

Dimensions (HxWxD): 8 x 16 1/2 x 3 3/8 in. (20.3 x 42 x

8.5 cm) approximate

Weight: 4.9 lb. (2.3 kg)

Approvals: Canadian Standards Association: Certified, File

No. LR76030

1 INSTALLATION PREPARATION

NOTES: Throughout these instructions, the following

terminology conventions are used:

• AQ251 refers to all of the AQ25142B, AQ25144B and

AQ25110B Control Panels. Where there are specific

instructions or details relating to the “-42B”, “-44B”, or

“-10B” Control Panels, the full model number (i.e.

AQ25144B) is used;

• Control Panel refers to an assembled product, con-

sisting of a transformer, Control Module and Zoning

Module, all contained within an AQ2000 panel enclo-

sure;

• AQ255 refers to all of the AQ25542B, AQ25542B,

AQ25582B and AQ25742B Expansion Zoning Panels,

and AQ257 refers to the AQ25744B Expansion Zon-

ing Panel. Where there are specific instructions or

details relating to the “-42B”, “-82B”, “-42B”, or

“-44B” Expansion Zoning Panels, the full model num-

ber (i.e. AQ25744B) is used;

• Expansion Zoning Panel refers to an assembled

product, consisting of a Zoning Module and—if appli-

cable—a transformer, contained within an AQ2000

panel enclosure; Expansion Zoning Panels are avail-

able in either 4-zone or 8-zone configurations. See

Table 1 in “AQ2000 Series Expansion Zoning Panels”

(form no. 69-1981) for specific models.

• AQ151 refers to the AQ15100B Control Module -

within an AQ251 Series Control Panel.

• Control Module refers to the component within an

AQ251 Series Control Panel that performs the “mas-

ter control operations”. See Table 1 for specific mod-

els.

• Zoning Module refers to the component within the

AQ251 Series Control Panel that controls zoning

operations;

• AQ155 refers to the AQ15540B Zoning Module and

AQ157 refers to the AQ15740B Zoning Module.

When Installing this Product…

1. Read these instructions carefully. Failure to follow

them could damage the product or cause a

hazardous condition.

2. Check the ratings given in the instructions and on

the product to make sure the product is suitable for

the application.

3. Installers must be trained, experienced, and licensed

service technicians.

4. Follow local codes for installation and application.

5. After installation is complete, check out the product

operation as printed in these instructions.

WARNING

Risk of electrical shock.

Can cause severe injury, property damage or death.

Disconnect power supply before installation and before

servicing.

Check That You Have All the

Necessary Equipment For a

Successful Installation

• AQ2000 Series components:

— AQ251 Control Panel

— AQ Expansion Zoning Panels (if more than four space-

heating zones in the system)

— Digital Thermostats (one for every space-heating zone

being controlled)

• Boiler supply and return temperature sensors and

secondary loop sensor (included with the AQ251 Control

Panel)

• Outdoor temperature sensor (included with AQ251 Control

Panel)

• Low voltage thermostat wire

• Zoning equipment (zone valves or pumps)

Read All Instructions Carefully

Before Proceeding

The AQ251 Control Panels are a part of a totally new series of

hydronic controls. And although they - and other AQ2000

system components - are very easy to install and operate, they

are different than other hydronic controls that you have

previously installed. So take a moment to read through this

quick installation guide before

beginning the installation.

Failure to follow them could damage the product or cause a

hazardous condition.

Familiarize Yourself With the AQ251

Control Panel Layout

Refer to Fig. 1. All AQ251 Control Panels consist of three

functional components:

1. AQ10X38 transformer (power supply module), which

connects to 120 Vac power and supplies 24 Vac power to

the Control Module and Zoning Modules

2. AQ15100B boiler/DHW Control Module, which controls

the boiler and domestic hot water (DHW) functions, as

well as coordinating the overall operation of the hydronic

system.

3. One of two different 4-zone Zoning Modules:

• AQ15740B (part of the AQ25144B Control Panel) for

zoning with 24 Vac zone valves with

end switches

• AQ15540B (part of the AQ25142B Control Panel) for

zoning with either line voltage circulators or 24 Vac

zone valves without

end switches.

AQ251 Control Panels can control a maximum of 16 zones by

connecting additional Expansion Zoning Panels to the AQ251

Control Panel. Each Expansion Zoning Panel is configured with

its own bank of DIP switches, located in the left-most section of

each Zoning Module.

AQ251 SERIES BOILER RESET CONTROL PANELS

69-1974—07 4

In general, the top terminals of the AQ2000 Series

components carry low voltage (24 Vac) power and the bottom

terminals carry line voltage (120 Vac) power. This is illustrated

in Fig. 1. The only exception to this is the AQ15540B Zoning

Module when used with low voltage zone valves (without end

switches). In this case, the bottom terminals of the Transformer

and Control Module carry line voltage (120 Vac), but the

bottom terminals of the Zoning Module will carry low voltage

(24 Vac) power.

The powered terminals on the bottom of the AQ2000 Series

Control Modules and Zoning Modules are connected internally,

as shown in Fig. 2. The voltage supplied to the N and L

terminals is also available at the adjacent terminal pairs when

the hot ( ) relays are switched.

Fig. 1. AQ251 Control Panel layout (AQ25142B shown).

Fig. 2. Internal wiring for AQ2000 Series components line voltage relays.

Home

M27736A

Zone 1

Zone 2

Zone 3

Zone 4

LOW

VOLTAGE

(24 V)

LINE

VOLTAGE

(120 V)

ZONING MODULE

TRANSFORMER

CONTROL MODULE

FOR THE AQ25142B TERMINALS CAN BE LINE VOLTAGE (IF USED WITH PUMPS) OR LOW VOLTAGE (IF USED WITH ZONE VALVES)

Home

M27737A

Zone 1

Zone 2

Zone 3

Zone 4

CONTACTS

SYMBOL

AQ251 SERIES BOILER RESET CONTROL PANELS

5 69-1974—07

2 MOUNTING

This section describes how to mount the Control Panel,

Expansion Zoning Panels, and the Thermostats.

Mount AQ251 Control Panel

Mount the control panel on the wall:

1. Use the template supplied with the AQ251 Series

Control Panel to mark mounting holes for panels

2. Install two top screws, mount the panel, and install the

two lower screws.

Mount Expansion Zoning Panel(s)

If there are Expansion Zoning Panels to install, mount them to

the wall now:

1. Remove wire channel plugs from the AQ251 Control

Panel and any Expansion Zoning Panels (see Fig. 3).

2. Mount Expansion Zoning Panel on the right-hand end of

the AQ251 Control Panel. Install two top screws of the

Expansion Zoning Panel, ensuring it is level with the

adjoining Control Panel, and install two lower screws.

3. Reverse wire channel plugs and re-insert them into their

slot, to form a wiring channel between the Control Panel

and the Expansion Zoning Panel (see Fig. 3) and to

connect the two panels together.

4. Repeat steps 1–3 for any additional Expansion Zoning

Panels.

Fig. 3. Orientation of wire channel plugs for creating pass-through wire channel and

for joining Control Panel to Expansion Zoning Panels.

Mount and Wire Thermostats in the

Zones

Install the thermostats on the walls in the zones that are to be

controlled by the AQ251 Control Panel.

When using AQ1000 thermostats refer to the installation

instructions (form #69-2005) included with the AQ1000

thermostats.

If not done already, run low voltage thermostat wire (24 gauge

or heavier) from the thermostats back to the Zoning Modules

connected to the AQ251 Control Panel.

NOTES: If not otherwise specified, low voltage wiring should

be run with 18 gauge thermostat wire and line voltage

wiring should be run with 14 gauge wire.

AQUATROL® line voltage screw terminals are only

approved for use with 22 to 12 gauge copper

conductors.

Several wiring diagrams are included in this

document. For additional information, refer to

http:// customer.honeywell.com or your local

distributor.

M23733A

WIRE

CHANNEL

PLUGS

WIRE

CHANNEL

PLUGS

AQ251 SERIES BOILER RESET CONTROL PANELS

69-1974—07 6

3 WIRING PROCEDURE

The AQ251 Control Panel is pre-wired at the factory, making for

faster installation:

• For all models, the low voltage output terminals located at

the top of the transformer are wired to the R and C input

terminals of the Control Module.

• For those Control Panel models that come with Zoning

Modules included, (all but the AQ25110B), the transformer’s

low voltage outputs are also wired to the R and C inputs of

the Zoning Module. The B-B “Exp. Bus” terminals of the

Control Module are wired to the B-B “Exp. Bus IN” terminals

of the Zoning Module.

Beginning with the top left of Fig. 4 and moving clockwise

around the panel, wire components to the AQ251 Control

Panel and Expansion Zoning Panels (if installed) in the

following six steps:

• “Step 1 – Transformer Wiring”

• “Step 2 – Control Panel Wiring”

• “Step 3 – Thermostats Wiring” on page 9

• “Step 4 – Zoning Equipment Wiring” on page 9

• “Step 5 – Line Voltage System Outputs” on page 12

• “Step 6 – Connection to Line Voltage Power” on page 13

Fig. 4. Wiring sequence.

Step 1 – Transformer Wiring

Factory pre-wiring of the Control Panels is shown as dotted

lines in Fig. 4.

In addition to the pre-wiring, run low voltage jumper wires from

available R and C terminals on the secondary of the

transformer to the R and C terminals of any Expansion Zoning

Panel.

Step 2 – Control Panel Wiring

Wire the Temperature Sensors, System Demands, Low

Voltage Outputs, and Communication Bus (Refer to Fig. 5 for

wiring terminals on the top of the AQ251):

• “Temperature Sensor Wiring” on page 7

• “System Demands Wiring” on page 7

• “Low Voltage Outputs Wiring” on page 8

• “Communication Bus Wiring” on page 8

Fig. 5. Low voltage wiring for the AQ15100B Control Module.

M27738A

Home

Zone 1

Zone 2

Zone 3

Zone 4

STEP 1 STEP 2 STEP 3

STEP 4STEP 5STEP 6

TO EXPANSION ZONING MODULES

(IF INSTALLED)

TO BOILER SUPPLY SENSOR

TO BOILER RETURN SENSOR

TO OUTDOOR SENSOR

IN FROM “R” TERMINAL ON

TRANSFORMER MODULE

(FACTORY-WIRED)

TO “T-T” TERMINALS ON

BOILER AQUASTAT

TO B-B “EXP.BUS IN”

TERMINALS ON CONNECTED

ZONING MODULE

TO SETPOINT LOAD

(OPTIONAL)

TO DHW AQUASTAT

IN FROM “C” TERMINAL

ON TRANSFORMER MODULE

(FACTORY-WIRED)

M27739A

TO LOW VOLTAGE AUXILIARY

DEVICE (OPTIONAL)

TO AUXILIARY INPUT

SWITCH (OPTIONAL)

TO MODULATING INPUT

ON BOILER

AQ251 SERIES BOILER RESET CONTROL PANELS

7 69-1974—07

Temperature Sensor Wiring

Connect the lead wires of each sensor to the corresponding

terminals on top of the AQ151 Control Module. See Fig. 5 on

page 6.

The Boiler Supply, Return and Secondary loop sensors can be

installed either as strap-on sensors or inserted into an

immersion well that is packed with thermally-conductive paste.

BOILER SUPPLY AND RETURN SENSORS.

Both

the Supply and Return Sensors should be installed on the

supply and return piping of the boiler for proper operation of the

AQ251 Control Panel. Even if the AQ251 is connected to a

modulating condensing boiler with its own supply and/or return

sensors, the AQ251’s sensors should still be installed for the

control to operate.

The Boiler Supply water sensor should be installed on the

supply piping close to the exit port of the boiler, using one of

the AQ12C11 strap-on sensors supplied with the AQ251. See

Fig. 6.

The Boiler Return sensor should be installed on the return

piping as close to the entrance port to the boiler as practical,

using the other AQ12C11 strap-on sensor supplied with the

AQ251.

The correct location is one that will measure the temperature of

all combined sources of water returning back to the boiler.

Insulate strap-on sensors with pipe wrap to ensure accurate

boiler temperature sensing.

The Boiler Supply and Return water sensors come with 10 ft.

(3m) of wire to minimize the need for splicing.

Fig. 6. Strap-on temperature sensor installation.

OUTDOOR SENSOR

The outdoor sensor should be located:

• in a shady location out of direct sunlight

• at least three feet from dryer, bathroom, or other vents

• above the expected snow line where ice and debris cannot

cover it

• on the north side of the building.

See Fig. 7 for typical placement. Outdoor sensor comes with

10 ft. (3m) of wire to facilitate splicing the sensor on the interior

of the building. Alternatively, if the building is equipped with a

continuous fresh air supply using, for example, an air-to-air

heat exchanger, the outdoor sensor may be installed in the

insulated portion of the ventilation intake duct, taking care not

to expose the sensor to direct or indirect sunlight.

Fig. 7. Outdoor temperature sensor installation.

IMPORTANT

Do not run sensor wires parallel, or close, to

telephone, Ethernet, or power cables. Cross all

power, Ethernet, and telephone wiring at right angles.

If sensor wires are located in an area with strong

sources of electromagnetic interference, or EMI, (e.g.,

if sensor wires are run in the same electrical chase as

line voltage wiring) use twisted pair, shielded cable, or

run wires in a grounded metal conduit. This is

important, since the calculated temperature - based

on the sensor's resistance reading - can be distorted

by high EMI, potentially causing the AQ251 to not

operate properly. If using shielded cable or conduit,

connect the shield wire to earth ground only

at the

AQ251 panel. Do not

ground the shield or conduit at

any other location or electromagnetic shielding will be

ineffective. If shielded cable is used, Honeywell

recommends the use of shielded cable with a

continuous ground plane, such as foil, with an integral

drain wire for bonding to earth ground.

System Demands Wiring

Additional information about settings for the various System

Demands is discussed in Table 6 on page 30.

AUX-IN

If the optional Aux In. contacts (terminals 9 and 10) will be

used, wire them now. These inputs are powered with 24 Vdc

and must connect only

to a dry closure contact (unpowered

switch).

The Aux-In contact closure sets the system into a specific

state, as determined by the installer setup using the

EQUIPMENT SETUP > AUXILIARY I/O sub-menu (see

Fig. 25 on page 39).

HEAT DEMAND

If the optional Heat Demand (terminals 11 and 12) will be used,

wire them to a system setpoint demand (dry contact closure),

such as a pool or spa Aquastat®.

The HEAT contact closure drives the system to control either at

the Reset temperature or the Setpoint temperature, as

determined by the installer setup using the EQUIPMENT

SETUP > ZONING > HEAT DMND selection (see Fig. 25 on

page 39). Heat Demand priority allows only heat for the first 30

M13763

M13775

AQ251 SERIES BOILER RESET CONTROL PANELS

69-1974—07 8

minutes of a call for heat and then allows the space heating

needs to be added in for the next 30 minutes. This cycle

continues until the call for heat is satisfied.

DOMESTIC HOT WATER

Wire the DHW (terminals 13 and 14) to the Aquastat or

thermostat on the domestic hot water tank.

DHW priority allows only DHW heat for the first 30 minutes of a

call for DHW and then allows the space heating needs to be

added in for the next 30 minutes. This cycle continues until the

call for DHW is satisfied.

NOTE: If the AQ251 is connected to a modulating

condensing boiler with built-in DHW

management, the DHW tank’s Aquastat should be

connected to the AQ251's DHW (terminals 13 and

14). The AQ251's Aux. Out (terminals 19 and 20)

should be wired to the boiler's DHW input

terminals to the AQ251. In this case, the Aux Out

contacts should be programmed (in Installer

Mode settings) to close when there's a call for

DHW [EQUIPMENT SETUP>AUXILIARY IO>

AUX.OUT>DHW]

Low Voltage Outputs Wiring

10 VDC

The 10 Vdc terminals (15 and 16) of the AQ251 produce a

modulating (0-10 Vdc or 2-10 Vdc) signal that can drive a

modulating boiler’s combustion fan to maintain a constant

supply temperature from the boiler (generally equal to the

Boiler High Limit setting in the EQUIPMENT SETUP > BOILER

SETTINGS sub-menu).

Boiler Signal: If the AQ251 panel is configured to send a

0-10V or 2-10V signal to a modulating/condensing

boiler, connect the AQ251’s modulating output terminals

(15 and 16) to the modulating signal input on the boiler

control.

BOILER

Wire the Boiler dry contact output (terminals 17 and 18) to the

T-T terminals on the boiler Aquastat or the boiler's control

panel. See Fig. 15 on page 12 for wiring connections to a

typical boiler Aquastat.

These contacts are made any time the system has a request

for boiler operation, unless the water supply temperature is

above the target temp at that time, at which time the system

primary boiler pump would come on.

AUX-OUT

If the Auxiliary Out low voltage output will be used, wire it now

to the device that will be switched when the Auxiliary Out’s dry

contacts close. Wire the hot leg of the device through the Aux.

Out connection (terminals 19 and 20).

The Aux-Out relay contacts close to correspond with an action

as determined by the installer setup using the EQUIPMENT

SETUP > AUXILIARY I/O sub-menu (see Fig. 25 on page 39).

NOTE: The Aux. Out contacts are rated for low voltage

devices only.

Communication Bus Wiring

All AQ2000 components communicate with each other on the

AQUATROL network using communication bus wiring. This

wiring must

connect all AQ2000 components. Otherwise,

features that depend on this networked communication (e.g.,

zone synchronization, outdoor temperature displayed on

thermostats, etc.) will not function.

The communication bus wiring is polarity insensitive. The

installer does not need to worry about a +ve or –ve orientation

of the wires. If there are two wires connected between the B-B

Bus Exp. In on one module and B-B Bus Exp. Out on another

module, there will be communication. See example in Fig. 8 for

how this wiring is to be installed.

The communication bus connections for AQ251 Control Panels

are pre-wired at the factory. If connecting an Expansion Zoning

Panel to an AQ25110B, wire the Control Panel’s B-B “Exp.Bus”

terminals (21-22) to the B-B “Exp. Bus IN” terminals (3-4) of

the Expansion Zoning Panel.

Fig. 8. Wiring for communication bus.

Zone 1

Zone 2

Zone 3

Zone 4

Zone 1

Zone 2

Zone 3

Zone 4

M27740A

DATA BUS

COMMUNICATION

WIRING

AQ25744B

AQ25142B

Home

AQ251 SERIES BOILER RESET CONTROL PANELS

9 69-1974—07

Step 3 – Thermostats Wiring

NOTE: The new AQ2000 panels will work with either digi-

tal (electronic) non-communicating thermostats

or AQ1000 communicating thermostats.

1. Using low voltage thermostat wire, connect one

thermostat from each zone to the corresponding

THERMOSTATS Zone X inputs on top of the Zoning

Module (see Fig. 9).

2. If there are additional zones (on Expansion Zoning

Panels) connected to this Zoning Module, run low

voltage thermostat wiring from the B-B Exp. Bus Out

connection (terminals 13 and 14) of the Zoning Module

to the B-B Exp. Bus. In connection (terminals 3 and 4) on

the Expansion Zoning Panel.

IMPORTANT

Do not run thermostat wires parallel, or close, to

telephone, Ethernet, or power cables. Cross all

power, Ethernet, and telephone wiring at right angles.

If thermostat wires are located in an area with strong

sources of electromagnetic interference, or EMI, (e.g.,

if thermostat wires are run in the same electrical

chase as line voltage wiring) use twisted pair,

shielded cable, or run wires in a grounded metal

conduit.

This is important, because the AQ1000 thermostats

are communicating thermostats which send and

received data via the two wires connecting them to

the Zoning Module. This data can be distorted by the

EMI, potentially causing the AQ251 to not operate

properly.

3. Run low voltage thermostat wiring from the R and C

terminals on the AQ251 Control Panel’s transformer to

the R and C terminals on the Expansion Zoning Panel.

As an alternative, you can run low voltage thermostat

wiring from the R and C terminals on the Zoning Module

to the R and C terminals on the Expansion Zoning Panel.

Fig. 9. Connecting AQ1000 thermostats.

Step 4 – Zoning Equipment Wiring

Because the Zoning Module of the AQ25142B Control Panel

can be used with either low voltage zone valves (without end

switches) or line voltage pumps or valves, field installed wiring

of the correct voltage needs to be connected to the zoning

equipment terminals on the bottom left portion of the Zoning

Module.

Line Voltage – Circulators or Zone Valves

Refer to Fig. 10. Remove the plastic wiring barrier that is

located in the bottom wiring channel between the AQ15100B

Control Module and the Zoning Module. Run jumper wires from

the N and L terminals on the bottom of the AQ251 Control

Panel’s transformer, through the wiring channel across the

bottom of the Control Panel, and to the corresponding N and L

terminals of the Zoning Module.

Fig. 10. Wiring an AQ15540B Zoning Module for use

with line voltage circulators.

Low Voltage – Zone Valves With or Without

End Switches

Wire using step 1 for zone valves without end switches, or use

step 2 for zone valves with

end switches:

1. Low voltage zone valves without

end switches:

Using Fig. 12 on page 10 as a guide, run jumper wires

from the R and C terminals on the secondary of the

AQ251’s transformer, through the wiring channel across

the top of the Control Panel, and down through the wiring

channel on the right side of the panel and over to the R

and C terminals on the bottom of the Zoning Module.

IMPORTANT

If low voltage zone valves are used with the

AQ25142B Control Panel, the supplied Low Voltage

Output sticker (shown in Fig. 11) must

be applied

over the line voltage output sticker (see Fig. 10) that is

already attached to the Zoning Module.

Fig. 11. Low voltage output sticker.

FROM B-B “EXP. BUS”

TERMINALS ON

CONTROL MODULE

TO B-B “EXP. BUS IN” TERMINALS

ON CONNECTED ZONING MODULE

(IF AN EXPANSION ZONING PANEL

IS CONNECTED)

THERMOSTAT ON ZONE 1

THERMOSTAT ON ZONE 2

THERMOSTAT ON ZONE 3

THERMOSTAT ON ZONE 4

M13776C

FROM LINE VOLTAGE

120V TERMINALS

(N AND L) ON BOTTOM

OF TRANSFORMER

M27687

M27688A

AQ251 SERIES BOILER RESET CONTROL PANELS

69-1974—07 10

Fig. 12. Wiring an AQ15540B Zoning Module for use

with low voltage zone valves without

end switches.

2. Low voltage zone valves with end switches:

See Fig. 13. 24 Vac power is pre-wired between the

transformer secondary at the top left of the AQ251’s

transformer and the AQ15740B Zoning Module. No field

wiring is required.

Fig. 13. Wiring an AQ15740B Zoning Module for use

with low voltage zone valves with

end switches.

NOTE: When wiring zone valves with end switches, note

the transformer's VA:

If low voltage zone valves with end switches are

used for zone control, make sure the selected

zone valves do not draw more power (VA) than the

38 VA capacity of the AQ10X38 transformer

supplied with the AQ251 Control Panel. This

integral transformer has enough power to operate

4 motorized zone valves (such as Honeywell

V8043E valves or 4 valves using low-amperage

draw, heat motor actuators, such as Honeywell

MV100 actuators), plus power the electronics of

the AQ251's Control Module and up to 16, AQ1000

thermostats. If zone valves with high-amperage-

draw heat-motor actuators are used (such as Taco

500 series zone valves), additional 24 Vac

transformer capacity will need to be wired to the

Zoning Module to power the valves. See

Fig. 14 on page 11 for recommended wiring of

additional low voltage VA capacity to AQ2000

Series Zoning Modules.

CAUTION

Equipment Damage Hazard.

Can damage internal circuitry of Zoning Module.

The ES1 and ES2 terminals of the AQ15740B Zoning

Module are powered terminals and must only

connected to a set of dry contacts, such as a zone

valve motor's end switch. If power is applied to these

contacts (for example, by running line voltage through

the zone valves’ end switches to bring on a circulator

feeding those valves), the internal circuitry of the

Zoning Module will be damaged, in which case the

warranty for this product will be voided.

FROM LOW VOLTAGE

24 VAC TERMINALS

(C AND R) ON TOP

OF TRANSFORMER

M M M M

M27689A

M27690A

AQ251 SERIES BOILER RESET CONTROL PANELS

11 69-1974—07

Fig. 14. Wiring of additional low voltage VA capacity.

THERMOSTATS

ZONE 1 ZONE 2 ZONE 3

ZONE 4

M27741A

THERMOSTATS

ZONE 1 ZONE 2 ZONE 3

ZONE 4

Zone 1

Zone 2

Zone 3

Zone 4

USING AN AQ15740B

VALVE ZONING MODULE

POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED.

Zone 1

Zone 2

Zone 3

Zone 4

24 VAC

100 VA

TRANSFORMER

115 VAC

24 VAC

100 VA

TRANSFORMER

USING AN AQ15540B

PUMP ZONING MODULE

AQ251 SERIES BOILER RESET CONTROL PANELS

69-1974—07 12

Step 5 – Line Voltage System Outputs

Refer to Fig. 15 and follow the steps in this section to wire

these devices to the AQ251 Control Module.

“1. Boiler Pump”

“2. DHW Device”

“3. Line Voltage Rated Aux Output (Aux. pump)” on page 13

Fig. 15. Line Voltage Connections for AQ251.

1. Boiler Pump

Connect the N and L wires of the boiler loop pump to the N and

switched hot terminals of the line voltage Boiler output, shown

in Fig. 17 on page 13. The ground wire of the pump can be

connected to any of the 8 ground screw terminals located on

the back surface of the Control Panel enclosure.

The boiler pump contacts are made after any one of the

following occur:

• A call for heat has occurred from any heating zone.

• The Heat input is shorted on terminals 11 and 12.

• The DHW input is shorted and

the DHW type is configured

as a valve.

The pump is delayed for the FIRE DELAY programmed in the

EQUIPMENT SETUP > BOILER OPERATION sub-menu (see

Fig. 25 on page 39). The boiler pump and the last zone calling

remain on in order to move heat out of the boiler for the period

of time programmed in the Purge time menu under the fire

delay. Manually adjusting thermostats affects the operation of

this software so it can not be tested manually, you must

observe it under normal operating conditions.

NOTE: If the AQ251 is connected to a modulating

condensing boiler, the boiler pump may need to

be connected to the boiler, not

the AQ251.

Confirm this with the boiler’s installation manual.

2. DHW Device

Wire the DHW pump or line voltage zone valve to the N and

switched hot terminals of the DHW output, as shown in

Fig. 17 on page 13.

If using a low voltage zone valve, wire the primary of a spud-

mounted transformer (115V to 24V) to the DHW line voltage

contacts and connect the low voltage zone valve to the

secondary terminals of this transformer. A spud-mounted

transformer may be located in one of the conduit knockouts on

the bottom of the AQ251 Control Panel.

Alternatively, a 24 Vac zone valve can be connected to the Aux.

pump line voltage-rated dry contacts, which can be configured

to close on a DHW call. This configuration is defined in the

Installer Equipment Setup menu beginning on page 30.

The DHW contacts are made when the DHW inputs on

terminals 13 and 14 are shorted by the controlling Aquastat.

This is a line voltage output designed to go to the DHW pump.

If 24 Vac is needed for a low voltage valve, you can mount a

step-down transformer on the conduit opening and wire the

valve from the transformer. When DHW is enabled, the system

has a 30-minute priority over all calls for heat. After 30 minutes,

calls for heat are added back in to the operation for 30 minutes

and then turned off again. This repeats until the DHW is

satisfied.

L8148, L7148

R8184A, R7184

BURNER AND

IGNITION

C554

BLACK

WHITE

ORANGE

POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED.

(HOT)

TO AUXILIARY DEVICE

(INSTALLER-DEFINED)

BOILER

PUMP

M27742A

TO LINE VOLTAGE 120V

TERMINALS (N AND L) ON

BOTTOM OF TRANSFORMER

FROM LINE VOLTAGE 120V

TERMINALS (N AND L) ON

BOTTOM OF TRANSFORMER

TO BOILER

TERMINALS 17-18

ON TOP OF AQ15100B

CONTROL MODULE

+ 28 hidden pages