Defrost System (Xp14-Xxx-230-01 Through 07) - Lennox XP14-018-230-06 Nstallation And Service Instructions

Enter the TEST mode by placing a shunt (jumper) across
the TEST pins on the board after power-up. The TEST
pins are ignored and the test function is locked out if the
shunt is applied on the TEST pins before power-up. Board
timings are reduced, the low-pressure switch is ignored
and the board will clear any active lockout condition.
NOTE - The 30-second off cycle is NOT functional when
jumpering the TEST pins.
Ambient Sensor—The ambient sensor (shown in figure
1) considers outdoor temperatures below -35°F (-37°C) or
above 120°F (48°C) as a fault. If the ambient sensor is
detected as being open, shorted or out of the temperature
range of the sensor, the board will not perform demand
defrost operation. The
time/temperature defrost operation and will display the
appropriate fault code. Heating and cooling operation will
be allowed in this fault condition.
Coil Sensor—The coil temperature sensor (shown in
figure 1) considers outdoor temperatures below -35°F
(-37°C) or above 120°F (48°C) as a fault. If the coil
temperature sensor is detected as being open, shorted or
out of the temperature range of the sensor, the board will
not perform demand or time/temperature defrost
operation and will display the appropriate fault code.
Heating and cooling operation will be allowed in this fault
condition.
Defrost System - (XP14-XXX-230-01
through 07)
The defrost control board has three basic operational
modes: normal, calibration, and defrost.
board will revert
Normal Mode—The demand defrost board monitors the
O line, to determine the system operating mode
(heat/cool), outdoor
temperature (outdoor coil) and compressor run time to
determine when a defrost cycle is required.
Calibration Mode—The board is considered uncalibrated
when power is applied to the board, after cool mode
operation, or if the coil temperature exceeds the
termination temperature when it is in heat mode.
Calibration of the board occurs after a defrost cycle to
ensure that there is no ice on the coil. During calibration,
the temperature of both the coil and the ambient sensor
are measured to establish the temperature differential
which is required to allow a defrost cycle.
to
Defrost Mode—The following paragraphs provide a
detailed description of the defrost system operation.
Defrost Cycles—The demand defrost control board
initiates a defrost cycle based on either frost detection or
time.
S
Frost Detection—If the compressor runs longer than
30 minutes and the actual difference between the clear
coil and frosted coil temperatures exceeds the
maximum difference allowed by the control, a defrost
cycle will be initiated.
IMPORTANT - The demand defrost control board will
allow a greater accumulation of frost and will initiate
fewer defrost cycles than a time/temperature defrost
system.
S
Time—If six hours of heating mode compressor run
time has elapsed since the last defrost cycle while the
coil temperature remains below 35°F (2°C), the
demand defrost control will initiate a defrost cycle.
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ambient temperature, coil