AQ251 SERIES BOILER RESET CONTROL PANELS
69-1974—04 32
DOMEST.HOT
WATER
Settings that the AQ251 uses to manage Domestic Hot Water generation
DHW ENABLE / DISABLE ENABLE Identifies whether Domestic Hot Water Management
function is enabled. DHW is typically disabled only if a
separate source of domestic hot water (e.g., oil, or gas-
fired hot water heater) is used.
DHW PRIO YES / NO NO Displays only if DHW = ENABLE.
Selects whether DHW generation can take priority over
space heating. If yes, set to YES; if not, set to NO.
PRIO.OVER. YES / NO YES Displays only if DHW PRIO = YES.
Selects whether (following a 30 minute uninterrupted call
for DHW Demand) the priority given to DHW generation
can be overridden to minimize the chance of freeze up or
excessive cool down of the space heating zones.
• YES = On = Allow DHW Priority override.
• NO = Off = Do not allow DHW Priority override.
If DHW Priority is selected, Honeywell strongly
recommends setting the DHW PRIOR.OVER to YES.
DHW DEVICE PUMP / VALVE PUMP Displays only if DHW = ENABLE.
Selects whether the DHW loop is supplied by a zone valve
or zone pump.
DHW VLV.OP 0 - 230 seconds
(in 5 second increments)
15
(seconds)
Displays only if DHW DEVICE = VALVE.
Time required for the DHW zone valve to fully open before
boiler loop pump is energized.
The 15 second default is typical for motorized valves.
DHW PURGE YES / NO YES Displays only if DHW = ENABLE.
Selects whether or not a purge should be applied after a
DHW demand has been served. If YES is selected, the
DHW pump or valve is kept running for the amount of time
programmed in the PURGE TIME option of the BOILER
OPERATION menu.
DHW SENSOR YES / NO NO Selects whether or not the Return sensor will be used as a
DHW tank sensor. YES = use as the DHW sensor.
DHW SETPOINT - -
60°F to 160°F (16°C to 71°C)
140°F
(60°C)
Displays only if DHW SENSOR = YES.
“- -” means Off (not used).
Target temperature set for the DHW tank.
DHW DIFF - -
5°F to 40°F (2.5°C to 22°C)
20°F
(-7°C)
Displays only if DHW SENSOR = YES.
“- -” means Off (not used).
• A call for DHW begins when the measured DHW
temperature = DHW SETPOINT - DHW DIFF and ends
when the DHW temperature = DHW SETPOINT.
• For example, if the DHW setpoint = 140°F and the DHW
Diff = 20°F, a call for DHW begins when the DHW
temperature falls below 120°F and ends when the DHW
temperature increases to 140°F.
DHW VACANCY - -
[41°F + DHW DIFF] to 160°F
([5°C + DHW DIFF] to 71°C)
45°F
(7°C)
Displays only if DHW SENSOR = YES.
“- -” means Off (not used).
Target DHW temperature when system is in VACANCY
mode
ZONING Settings which the AQ251 uses specifically for Zone operation
HT DMND PRIO YES / NO NO Selects whether a HEAT DEMAND (device connected to
the Heat terminals on the AQ control module) can take
priority over space heating. If yes, set to YES; if not, set to
NO.
• If both DHW Priority and Heat Demand Priority are set
to YES and both are active at the same time, DHW
Priority takes priority over Heat Demand Priority.
Table 6. Installer Menu – Equipment Setup. (Continued)
EQUIPMENT SETUP
Menu Option Range
Factory
Default Description
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