Defrost Control Board - Friedrich VERT-I-PAK VHA09K25RTQ Service Manual

OPERATION

Defrost Control Board

Inputs
C - 24 VAC Common
R - 24 VAC Input (Power Supply) supplied via the transformer.
Y - 24 VAC thermostat input for compressor demand - Thermostat Call for Compressor ("Y"). This signal is monitored by the control logic,
and is recognized as active when "R" is connected to "Y". Inputs of less than 11 VAC will not be detected as active.
B - 24 VAC thermostat input for reversing valve demand. Thermostat Call for Reversing Valve ("B"). This signal is monitored by the control
logic, and is recognized as active when "R" is connected to "B". The input signal is connected through the normally closed relay contacts of
K1 to the "RV" quick connect terminal.
P3 – Connections for outdoor ambient temperature sensor. Ambient Temperature Sensor ("AMB") The ambient temperature sensor is a
thermistor input. In addition to measuring the temperature value of the thermistor, the control shall detect an open thermistor condition,
and a shorted thermistor condition.
P4 - Connections for the Condenser temperature sensor: Coil Temperature Sensor ("COIL"). The coil temperature sensor is a thermistor
input. In addition to measuring the temperature value of the thermistor, the control shall detect an open thermistor condition, and a
shorted thermistor condition.
P1 5 position, P1 provides selection of the defrost terminate temperature based on the position of selection shunt. Selections include 50˚F,
60˚F, 70˚F, and 80˚F. If the temperature shunt is not installed, the default termination temperature shall be 50˚F. The control shall be
provided from the factory with the temperature shunt installed in the 70˚F position.
HI -PS High pressure switch input. The high-pressure switch input is a 24 VAC input. The input is supplied from the "Y" thermostat input,
is in series with the compressor contactor output, and is monitored by the control logic. The hp switch Opens at 675 psig and closes at 475
psig.
LO - PS Low pressure switch input 3.9 Low Pressure Switch ("LO-PS") The low-pressure switch input is a 24 VAC input. The input is
supplied from the "Y" thermostat input, is in series with the compressor contactor output, and is monitored by the control logic. The lp
switch opens at 30 psig and closes at 50 psig.
Outputs
Y out - (CC) Switched compressor contactor 24 VAC common. The control can be configured to provide a pilot duty 24 VAC output for the
compressor contactor. The Y out "Y" terminal is sourced 24 VAC from the "Y" input terminal. When the compressor contactor is to be
energized, 24VAC common is connected to the "CC" terminal.
Reversing Valve ("RV") B out
(RV) Switched 24 VAC to reversing valve.
(C) 24 VAC common to reversing valve.
The control provides a pilot duty 24 VAC output for the reversing valve. This output provides a normally closed relay connection between the
"B" and "RV" terminals. This connection is opened during a defrost cycle.
D - 24 VAC auxiliary heat output (sourced from Y input) The control provides a pilot duty 24 VAC output during defrost operation. For defrost
operation of the auxiliary heat, the "D" output is connected to the 24 VAC through the high pressure switch which is sourced by the "Y"
thermostat input.
FAN - 240 VAC line voltage source for PSC condenser fan. The control provides a 240 VAC line voltage output for the condenser fan. The
condenser fan output is a normally closed relay contact output. During the defrost operation, the normally closed contacts of the K2 relay
will be opened.
Diagnostic Indicator LED ("LED1" & "LED2")
Two red LED's are provided to display diagnostic codes for the control.
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