Specifications

AQUATROL Zoning System
70-6910 209
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AQ251 Electronic Boiler Reset Control Panel for
Hydronic Zoning System
The AQ251 family of AQUATROL Boiler Reset Controls provides
simplified, energy-efficient outdoor temperature compensated
control of single temperature, residential hydronic heating
systems. The AQ251 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 with outdoor reset for in-creased energy efficiency with
reduced boiler cycling. AQ251 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 communicating thermostats (AQ25142B
and AQ25144B) or most digital dry contact thermostats (AQ25110B,
AQ25142B, and AQ25144B).
• 0-10 Vdc modulating output for driving a modulating/condensing
boiler.
• Displays outdoor temperature on all AQ1000 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.
• Central programming of zone set points and setback.
• Controls up to 2 stages of heat from a single thermostat.
• Zoning Control for up to four 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 AQ254 Add-a-Temperature expansion
panels.
• Outdoor temperature compensation (reset), or Load reset based on
indoor temperature feedback.
• 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.
Application: Boiler reset control for hydronic zoning system
Dimensions, Approximate
AQ25110B: 13 in wide x 8 in. high x 3 3/8 in deep
(33 cm wide x 20.3 cm high x 8.5 cm deep)
AQ25142B and AQ25144B: 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)
Power Supply: 120V/60Hz
User Interface (Setting, Programming): (LCD Display and a 7 button
Key Pad)
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
Setback Program: 7 day, up to 2 setback periods/day.
Boiler Design Temperature: 80F to 210F (26C to 99C)
Boiler (Supply) Min. Control Temperature: OFF, 59F to 180F (OFF,
15C to 82C)
Boiler (Supply) Max. Control Temperature: (OFF, 120F to 225 F)
OFF, 49C to 107 C
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 Demand Input: External dry contacts connection only
Outdoor Low Design Control Temperature: -60F to 32F
(-51 C to 0 C)
Return Minimum Control Temperature: 80 F to 180 F (27C to 82C)
Pump/Valve exercise: 30 seconds per 2 weeks of space heating
inactivity
Auxiliary Pump Output Rating: Dry contact output, 120 Vac/250 Vac
5A, 1/3 HP
Auxiliary Low Voltage Output Rating: 24 V
ac, 0.5A, 12VA
Auxiliary (Demand) I
nput: External dry contacts connection only
WWSD (Warm Weather Shut Down) Temperature: Off, 35 F to 100 F
(Off, 1 C to 38 C)
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: External dry contacts
connection only
B-B Communication Bus Terminals: Low voltage, Class II, 2-wire
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
AQ25110B:
4.9 lbs (2.3 kg)
AQ25142B and AQ25144B: 5.7 lbs (2.6 kg)
Approvals:
Canadian Standards Association: CSA C/US Certified to CSA and
UL Standards, File No. LR76030