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Defrost Control Board
The defrost thermostat, defrost pressure switch and the de
frost control work together to ensure that the heat pump
outdoor coil does not ice excessively during the heating
mode.
Compressor Accumulated Run-Time Interval
The defrost control will not energize a defrost cycle unless
the unit has been operating in heating mode for an accumu
lated 60 minutes (default) on 100269-02 boards; 90 min
utes (default) on 100269-04 boards. The run time interval
can be changed by moving the jumper on the CMC board
timing pins. See figure 6.
The defrost interval can be adjusted to 30, 60, or 90 min
utes. The defrost timing jumper is factory-installed to pro
vide a 60-minute defrost interval. If the timing selector
jumper is not in place, the control defaults to a 90-minute
defrost interval.
Defrost Test Option
A TEST option is provided for troubleshooting. The TEST
mode may be started any time the unit is in the heating
mode and the defrost thermostat is closed or jumpered
.
If
the timing jumper is in the TEST position at power‐up, the
defrost control will ignore the test pins. When the jumper is
placed across the TEST pins for two seconds, the control
will enter the defrost mode. If the jumper is removed before
an additional 5-second period has elapsed (7 seconds to
tal), the unit will remain in defrost mode until the defrost
pressure switch opens or 14 minutes have passed. If the
jumper is not removed until after the additional 5-second
period has elapsed, the defrost will terminate and the test
option will not function again until the jumper is removed
and re-applied.
Diagnostic LEDs
The defrost board uses two LEDs for diagnostics. The
LEDs flash a sequence according to the condition.
TABLE 1
Defrost Control Board Diagnostic LED
Indicates
LED 1
LED 2
Normal operation /
power to board
Synchronized Flash
with LED 2
Synchronized
Flash with LED 1
Board failure /
no power
Off
Off
Board failure
On
On
Anti-short cycle
lockout
Alternating slow flash
DEFROST CONTROL BOARD CMC1
FIGURE 6
DIAGNOSTIC
LEDS
100269-02:INSTALLED AT
THE FACTORY TO DISABLE
COMPRESSOR DELAY
100269-04:REMOVED AT
THE FACTORY TO DISABLE
COMPRESSOR DELAY
TIMING JUMPER
100269-02: 60 MINUTES
100269-04: 90 MINUTES
