
AQUATROL Zoning System
AQ25A Programmable Relay Control Panel for Hydronic Zoning 
System
• Displays outdoor temperature on all AQ1000 Series thermostats 
when used with an AQ12C10 outdoor sensor (included). 
• Intuitive programming interface and armchair programming (can be 
programmed at your desk and taken to the job site “ready-to-install”). 
• Customizable control settings and schedules allow for greater level 
of control and comfort. 
• Controls up to 2 stages of heat from a single thermostat. 
• Central programming of zone set points and setbacks 
• Zoning Control for up to 4 zones as shipped; can be expanded to a 
total of 16 zones with AQ255 or AQ257 expansion zoning panels, 
and up to 64 zones when used with AQ254 Add-a-Temperature 
panels. 
The AQ25A family of AQUATROL Programmable Relay Boiler 
Controls provides simplified, energy-efficient control of singletemperature, residential hydronic heating systems. The AQ25A 
easily converts a single zone heating system into a room-by-room 
comfort control system, or upgrades a basic, relay-logic zoning 
system to intelligent Zone of Greatest Demand control for increased energy efficiency with reduced boiler cycling. AQ25A 
boiler controls can ensure ample supply of hot water for both 
space heating and priority generation of domestic hot water for 
bathing, dishes and laundry.
• Use with AQ1000 2-wire dry contact communicating thermostats and 
most digital thermostats. 
• 0-10 Vdc modulating output for driving a modulating/condensing 
boiler. 
Application: Boiler control for zoned hydronic systems 
Dimensions, Approximate: 16 1/2 in wide x 8 in. high x 3 3/8 in deep 
(42 cm wide x 20.3 cm high x 8.5 cm deep) 
Powe r Su pply: 120V/60Hz 
User Interface (Setting, Programming):  (LCD Display and a 7 button 
Key Pad) (DIP Switches on zoning modules) 
Electrical Connections (Line Voltage): Wire-clamp screw terminals, 
Maximum 2 x 14 AWG each on line voltage terminals
Control and Zoning Panel Temperature Rating: 32 F to 130 F (0 C to 
55 C) 
Thermostat Compatibility: AQ1000 Series 2-wire communicating 
thermostats and most digital thermostats
Zone Module Thermostat input: Low voltage, Class II, 2-wire polarity-
insensitive, digital communicating with power link to AQ1000 series 
thermostat.
Setback Program: 7 day, up to 2 setback periods/day. 
Boiler Heat Post Purge: Off, 10 seconds to 30 minutes (factory default 
is 30 seconds)
Boiler (T-T) Output Rating: 24 Vac, 0.5A, 12VA 
Boiler Differential: 2F to 41F (1C to 23C), or Auto (minimum 2 minutes 
on time)
DHW Pump/Valve Output Rating: 120 Vac/250 Vac 5A, 1/3HP 
DHW Demand Input: External dry contacts connection only 
Pump/Valve exercise: 30 seconds per 2 weeks of space heating 
inactivity
• Zone synchronization through Zone of Greatest Demand control. 
• Domestic hot water priority and priority override protection. 
• Line or low-voltage output for zoning equipment (pumps or valves). 
• Boiler short cycling protection. 
• Boiler post purge. 
• Freeze protection. 
• Pump/valve exercise. 
• Boiler shock prevention from cold water returning to boiler. 
• Automated test and purge feature for quick start-up and simplified 
troubleshooting. 
• Integral 38 VA transformer with self resetting electronic fuse. 
• 2 hour power supply (super-capacitor) to retain day and time settings 
during power outage. 
• Non-volatile EPROM memory retains program settings during power 
outage.
Auxiliary Pump Output Rating: Dry contact output, 120 Vac/250 Vac 
5A, 1/3 HP
Auxiliary Low Voltage Output Rating: 24 Vac, 0.5A, 12VA 
Auxiliary (Demand) Input: External dry contacts connection only 
Zone Output Contact Rating: Pumps: 120 Vac/250 Vac, 5A, 1/3 HP
Valves: 24 Vac, 0.5 A, 12 VA
Sensor Temperature Rating: -58 F to +230 F (-50 C to +110 C)  
Supply/Return Sensor: Lead Length: 10 ft. (3050 mm). 10 kilohm NTC 
thermistor at 25 C (77 F) ±0.5F (±0.3C) up to 500 ft (150 M) using 18 
AWG or larger wire
Heat Demand (Thermostat R-W) Input: 
connection only
B Communication Bus Terminals: Low voltage, Class II, 2-wire 
B-
polarity-insensitive, digital communicating link to other Control or 
Zoning modules.
R-C Input (on Control and Zoning Modules): 24 Vac Class II (input 
on Control and Zoning Modules)
R-C Output (on transformer): 38 VA, 24 Vac Class II 
Operating Humidity Range (% RH): 5 to 90% RH, non-condensing 
Weight: 5.7 lbs (2.6 kg)  
Approvals 
Canadian Standards Association: CSA C/US Certified to CSA and 
UL Standards, File No. LR76030
External dry contacts 
Type of 
Zoning 
Product Number
* AQ25A42B/U Zone pumps or 
* AQ25A44B/U Zone valves with 
* TRADELINE models • SUPER TRADELINE models
186 customer.honeywell.com 70-6910
Devices 
Controlled
2-wire valves 
(line voltage)
end switches
Number of 
Zones 
Controlled
4 120 Vac/250 
4 120 Vac/250 
Boiler Pump 
Output 
Rating
Vac 5A, 1/3HP
Vac 5A, 1/3HP
Weight
5.7 lbs 2.6 kg AQ15A00B boiler control module; AQ12C11 supply/return/mixed 
5.7 lbs 2.6 kg AQ15A00B boiler control module; AQ15740B 4-zone valve with 
Replacement Partslb kg
loop sensor; AQ12C10 outdoor sensor; AQ10X38 24 Vac 38 VA 
transformer; AQ15540B 4-zone pump expansion module
end switch expansion module; AQ12C11 supply/return/mixed 
loop sensor; AQ12C10 outdoor sensor; AQ10X38 24 Vac 38 VA 
transformer