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HPXA12 1.5 THROUGH 5 TON OPERATING SEQUENCE
Single and Three Phase
This is the sequence of operation for HPXA12 series units.
The sequence is outlined by numbered steps which corre-
spond to circled numbers on the adjacent diagram.
NOTE− The thermostat used may be electromechan-
ical or electronic.
NOTE− Transformer in indoor unit supplies power (24 VAC)
to the thermostat and outdoor unit controls.
COOLING:
1 − Internal thermostat wiring energizes terminal O by
cooling mode selection, energizing the reversing valve
L1. Cooling demand initiates at Y1 in the thermostat.
2 − 24VAC energizes compressor contactor K1 (5 minute
anti−cylce time must be satisfied first) .
3 − K1-1 N.O. closes, energizing compressor (B1) and out-
door fan motor (B4).
460V units only
− K1−1 closes energizing compressor
(B1) and outdoor relay K10 energizing outdoor fan
motor (B4).
4 − Compressor (B1) and outdoor fan motor (B4)
begin immediate operation.
END OF COOLING DEMAND:
5 − Cooling demand is satisfied. Terminal Y1 is de-ener-
gized.
6 − Compressor contactor K1 is de-energized.
7 − K1-1 opens and compressor (B1) and outdoor fan
motor (B4) are de-energized and stop immediately.
460V units only
− K1−1 opens de−energizing
compressor (B1) and outdoor relay K10 . Outdoor fan
(B4) is de−energized.
8 − Terminal O is de−energized when internal thermostat is
out of cooling mode, de−energizing the reversing valve
L1.
FIRST STAGE HEAT:
9 − Heating demand initiates at Y1.
10 − 24VAC energizes compressor contactor K1
(5 minute anti−cylce time must be satisfied first).
11 − K1-1 N.O. closes, energizing compressor and out-
door fan motor.
460V units only
− K1−1 closes energizing compressor
(B1) and outdoor relay K10 energizing outdoor
fan motor (B4).
12 − Compressor (B1) and outdoor fan motor (B4)
begin immediate operation.
END OF FIRST STAGE HEAT:
13 − Heating demand is satisfied. Terminal Y1 is
de-energized.
14 − Compressor contactor K1 is de-energized.
15 − K1-1 opens and compressor (B1) and outdoor fan
motor (B4) are de-energized and stop immediately.
460V units only
− K1−1 opens de−energizing
compressor (B1) and outdoor relay K10 . Outdoor fan
(B4) is de−energized.
DEFROST MODE:
16 − When a defrost cycle is initiated, the control ener-
gizes the reversing valve solenoid and turns off the
condenser fan. The control will also put 24VAC on
the W1" (auxiliary heat) line. The unit will stay in this
mode until either the coil sensor temperature is
above the selected termination temperature, the de-
frost time of 14 minutes has been completed, or the
room thermostat demand cycle has been satisfied.
(If the temperature select shunt is not installed, the
default termination temperature will be 100°F.) If the
room thermostat demand cycle terminates the
cycle, the defrost cycle will be held until the next
room thermostat demand cycle. If the coil sensor
temperature is still below the selected termination
temperature, the control will continue the defrost
cycle until the cycle is terminated in one of the meth-
ods mentioned above. If a defrost is terminated by
time and the coil temperature did not remain above
35°F (2°C) for 4 minutes, the control will go to the
34−minute Time/Temperature mode.
