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TPA*H4 SERIES
Table 8. Demand Defrost Control (A108) Inputs, Outputs and Configurable Settings
Control
Location
Control Label or
Description
Purpose Function
P1 TEST Test Mode See Test Mode on page 35 for further details.
P1 50, 70, 90, 100
Defrost Temperature Termina-
tion Shunt (Jumper) Pins
The demand defrost control has valid 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. Val-
id 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 sen-
sor.
(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
jumpering the TEST pins on P1.
P6 TST, PS DF, C, R, O, Y1, Y2 Factory Test Connectors No field use.
DS1 RED LED
Diagnostic LED
Valid states for demand defrost control’s two LEDs are OFF, ON
and FLASHING which indicate diagnostics conditions that are de-
scribed in tables 9 and 10.
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)
for 90 seconds following the start up 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 Line output 24VAC service light output.
24V 24V 24 Volt output
24VAC typically used to supply power to the Lennox System
Operation Monitor (LSOM)
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