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TABLE 3
DEMAND DEFROST CONTROL (A108) INPUTS, OUTPUTS AND CONFIGURABLE SETTINGS
Control
Locations
Control Label or
Description
Purpose Function
P1 50, 70, 90, 100
Defrost Temperature
Termination Shunt (Jumper)
Pins
The demand defrost control (illustrated in figure 17) has selections which
are: 50, 70, 90, and 100°F (10, 21, 32 and 38°C). The shunt termination
pin is factory-set at 50°F (10°C). If the temperature shunt is not installed,
the default termination temperature is 90°F (32°C).
P2
W1
24VAC Thermostat Input /
Output
24VAC input / output from indoor thermostat to indoor unit.
C 24VAC Common 24VAC common.
L Thermostat Service Light Thermostat service light connection.
R 24VAC 24VAC.
Y2 Thermostat Input Controls the second stage operation of the unit.
O Thermostat Input Reversing valve solenoid.
Y1 Thermostat Input Controls the operation of the unit.
P3 55, 50, 45, 40
Low Ambient Thermostat
Pins
Provides selection of the Y2 compressor lock-in temperature. Valid
options are 40, 45, 50 and 55 degrees Fahrenheit.
P4
DIS-YEL Coil Sensor
(P4-5) Ground connection for outdoor coil temperature sensor.
(P4-6) Connection for outdoor coil temperature sensor.
AMB-BLACK Ambient Sensor
(P4-3) Ground connection for outdoor ambient temperature sensor.
(P4-4) Connection for outdoor ambient temperature sensor.
COIL-BROWN Discharge Sensor No discharge sensor is used; replaced by 10K resistor.
P5 DELAY Delay Mode
The demand defrost control has a field-selectable function to reduce
occasional sounds that may occur while the unit is cycling in and out of
the defrost mode. When a jumper is installed on the DELAY pins, the
compressor will be cycled off for 30 seconds going in and out of the
defrost mode. Units are shipped with jumper installed on DELAY pins.
NOTE
- The 30-second off cycle is NOT functional when TEST pins on
P1 are jumpered.
P6 TST, PS DF, C, R, O, Y1, Y2 Factory Test Connectors No field use.
DS1 RED LED
Diagnostic LED
Demand defrost control LEDs may be OFF, ON, or FLASHING to
indicate diagnostic conditions which are described in table 3.
DS2 GREEN LED
FAN TWO CONNECTORS Condenser Fan Operation These two connections provide power for the condenser fan.
O OUT O OUT 24 VAC output 24 VAC output connection for reversing valve.
LO-PS LO-PS Low-Pressure Switch
When the low pressure switch trips, the demand defrost control will cycle
off the compressor, and the strike counter in the demand defrost control
will count one strike. The low pressure switch is ignored under the
following conditions:
during the defrost cycle and 90 seconds after the termination of
defrost
when the average ambient sensor temperature is below 0°F (-18°C)
during 90 seconds following the start of the compressor
during TEST mode.
Y2 OUT Y2 OUT 24 VAC Output 24 VAC output for second-stage compressor solenoid.
Y1 OUT Y1 OUT 24 VAC Common Output 24 VAC common output, switched for enabling compressor contactor.
HS-PS HS-PS High-Pressure Switch
When the high pressure switch trips, the demand defrost control will cycle
off the compressor, and the strike counter in the demand defrost control
will count one strike.
L L Service Light Output 24VAC service light output.
24V 24V 24 Volt output
24VAC typically used to supply power to the Lennox System Operation
Monitor (LSOM). Not used in this system.
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