Honeywell AQ25A Series Technical Reference Booklet page 138

AQ252 Universal Injection/Mixing Boiler Reset Control Panels
Menu Option
Installer-defined settings for the system design parameters (e.g., boiler supply and return
BOILER SETTINGS temperatures, reset mode, and outdoor low temperature)
HIGH LIMIT 120°F to 225°F (49°C to
107°C)
LOW LIMIT 60°F to 180°F (15°C to 82°C) 150°F
BOILER DIFF 2°F to 41°F (1°C to 23°C) /
AUTO
W.W.S.D. - -
35°F to 100°F (2°C to 38°C)
RESET OUTDOOR / LOAD / NONE
BOILER SETTINGS (continued)
OUTDOOR -60°F to 32°F (-51°C to 0°C)
LOW
BOILER DSGN 80°F to 210°F (27°C to 99°C) 180°F
MIN. RETURN - - / 80°F to 180°F (27°C to
82°C)
69-1986—02
Table 6. Installer Menu – Equipment Setup.
EQUIPMENT SETUP
Factory
Range Default
190°F
(88°C)
AUTO
70°F
(21°C)
OUTDOOR
10°F
(-12°C)
(82°C)
140°F
(60°C)
32
Description
Maximum temperature that the control can use as a target
for the boiler supply water (HIGH LIMIT cannot be set
below the LOW LIMIT setting).
Minimum temperature that the control can use as a target
for the boiler supply water (LOW LIMIT cannot be set
above the HIGH LIMIT setting).
The temperature differential used by the control when
operating the boiler. The same differential is used for both
the HIGH LIMIT and the LOW LIMIT.
• If AUTO is selected, the differential is calculated
automatically by the AQ252 to maximize comfort and
minimize boiler short cycling.
• If a specific boiler differential (BOILER DIFF) is
selected, the AQ252 will apply 1/2 of this differential
above the AQ252's HIGH LIMIT boiler setting and the
other 1/2 below the HIGH LIMIT setting when
controlling the boiler supply water temperature.
• For example, if the High Limit = 190°F and the Boiler
Diff = 10°F, the High Limit range becomes 185-195°F.
NOTE: This formula also applies to the boiler differential
around the AQ252's LOW LIMIT.
Warm Weather Shut Down is the outdoor temperature
above which the AQ252 will not allow hot water to be sent
to a space heating zone. The boiler still operates to supply
hot water to DHW or a setpoint (HEAT) demand. The
WWSD feature can be disabled by reducing the WWSD
temperature below 35°F (2°C), at which point the display
will read "- - ".
NOTE: Disabling WWSD is not advisable. This will
increase the average reset temperature for the
Boiler Supply water, resulting in higher energy
consumption and less even heating.
Selects the calculation method (algorithm) that the control
uses to set the target temperature for the boiler supply and
secondary loop supply water. Choose LOAD for buildings
with high internal heat gains; otherwise use OUTDOOR.
The lowest annual outdoor temperature for the location
where the system is installed, also referred to as the
Design Temperature. Typically used in the original heat
loss calculations for the building, the OUTDOOR LOW
temperatures for various cities in North America can
generally be found in ASHRAE tables.
The supply water temperature required from the boiler
when the outdoor temperature is at the OUTDOOR LOW
temperature.
Minimum temperature (or OFF) that the control allows for
water returning to the boiler.
If the temperature of the boiler return water is below the
selected temperature, and the AUX pump is set to operate
as a boiler bypass pump (EQUIPMENT SETUP >
AUXILIARY I/O > AUX.PUMP option is set to BYPASS),
the AUX dry contacts close, allowing the separately-
powered AUX pump to energize.
• "- -" means Off (not used).