Amana ANX, Service And Troubleshooting

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SYSTEM OPERATION
56
Cooling Cycle
For legacy room thermostat: When the room thermostat
calls for cool, the contacts of the room thermostat close
making terminals R to Y1 & G (if thermostat calls for low
stage cool), or R to Y1, Y2 & G (if thermostat calls for
high stage cool), the low voltage circuit of the transformer
is completed. Current now flows through the magnetic
holding coils of the compressor contactor (CC) and fan
relay (RFC). If thermostat calls for high stage cool, the
microprocessor on the UC board will also energize the
compressor high stage solenoid to run the compressor at
full capacity.
This draws in the normally open contact CC, starting the
compressor and condenser fan motors in either low or high
stage depending on the thermostat’s demand. At the same
time, contacts RFC close, starting the indoor fan motor.
When the thermostat is satisfied, it opens its contacts,
breaking the low voltage circuit, causing the compressor
contactor and indoor fan relay to open, shutting down the
system.
If the room thermostat fan selector switch should be set
on the “on” position, then the indoor blower would run
continuously rather than cycling with the compressor.
GSZ, ANZ, ASZ, SSZ, DSZ, and VSZ models energize
the reversing valve thorough the “O” circuit in the room
thermostat. Therefore, the reversing valve remains
energized as long as the thermostat subbase is in the
cooling position. The only exception to this is during
defrost.
For heat pumps, during cooling cycle the reversing valve is
energized as the room thermostat closes “O” terminal to R
and the microprocessor on the UC board responds to such
a condition by energizing the solenoid coil on the reversing
valve.
Defrost Cycle
The defrosting of the outdoor coil is jointly controlled by the
defrost control board and the defrost thermostat.
Solid State Defrost Control
During operation the power to the circuit board is controlled
by a temperature sensor, which is clamped to a return
bend (3/8” coils) or a feeder tube (5 mm coils) entering
the outdoor coil. Defrost timing periods of 30, 60, or 90
minutes may be selected by connecting the circuit board
jumper to 30, 60, or 90 respectively. Accumulation of time
for the timing period selected starts when the sensor closes
(approximately 31° F), and when the room thermostat calls
for heat. At the end of the timing period, the unit’s defrost
cycle will be initiated provided the sensor remains closed.
When the sensor opens (approximately 75° F), the defrost
cycle is terminated and the timing period is reset. If the de-
frost cycle is not terminated due to the sensor temperature,
a ten minute override interrupts the unit’s defrost period.
The new upgraded defrost control has a 12 minute override
interrupt.
Indoor
Coil
Accumulator
Bi-Flow
Filter Dryer
Outdoor
Coil
Thermostatic
Expansion
Valve
Check Valve
Reversing Valve
(De-Energized)
Indoor
Coil
Accumulator
Bi-Flow
Filter Dryer
Outdoor
Coil
Thermostatic
Expansion
Valve
Check Valve
Reversing Valve
(Energized)
Cooling Cycle