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Page 30
DEFROST CONTROL BOARD CMC1
FIGURE 21
DEFROST TEMPERATURE
TERMINATION JUMPER:
100135-06: 50
5
F(10
5
C)
24V TERMINAL
STRIP
CONNECTIONS
DIAGNOSTIC
LEDS
PRESSURE
SWITCH CIRCUIT
CONNECTIONS
COIL AND AMBI
ENT SENSOR
CONNECTIONS
REVERSING
VALVE
DELAY PINS
5- Defrost Controls (CMC1) - Continued
100135 Series Demand Defrost Control
After 34 minutes of heating mode operation, if the
difference between the ambient temperature
(RT13) and the coil temperature (RT21) is higher
than the maximum difference allowed by the
control, the defrost control will initiate defrost. The
defrost control will also initiate defrost after 6
hours of heating mode operation when coil
temperatures remain below 35
°
F (2
°
C). The
defrost cycle ends when the coil temperature is
higher than the termination temperature (50
°
F
default) or after 14 minutes of operation. If the
defrost is terminated by the 14-minute timer,
another defrost cycle will be initiated after 34
minutes of run time.
Note - The defrost termination temperature can be
adjusted to 50, 70, 90 or 100
5
F. The jumper termination
pin is factory-set at 50
5
F (10
5
C). If the temperature
jumper is not installed, the default termination
temperature is 90
5
F (32
5
C). See figure 21.
Defrost Control Board
The defrost control ensures that the heat pump outdoor
coil does not ice excessively during the heating mode.
The defrost control uses input from a defrost switch on
100269 series defrost control boards. The defrost control
uses input from a coil and an ambient temperature sensor
on 100135 series defrost control boards.
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 total), 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 9
Defrost Control Board Diagnostic LED
Mode
Green LED
(DS2)
Red LED (DS1)
No power to control
OFF
OFF
Normal operation /
power to control
Simultaneous Slow FLASH
Anti‐short cycle
lockout
Alternating Slow FLASH
Low pressure switch,
freezestat fault
OFF
Slow FLASH
Low pressure switch,
freezestat lockout
OFF
ON
High pressure switch
fault
Slow FLASH
OFF
High pressure switch
lockout
ON
OFF
*Ambient sensor fault Simultaneous FAST flash
*Coil sensor fault
Alternating FAST flash
*100135-06 board only