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13HPX OPERATING SEQUENCE
This is the sequence of operation for 13HPX series units.
The sequence is outlined by numbered steps which corre-
spond to circled numbers on the adjacent diagram. The
steps are identical for both cooling and first stage heating
demand with the exception reversing valve L1 is energized
during cooling demand and de−energized during heating
demand.
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:
Internal thermostat wiring energizes terminal O by cooling
mode selection, energizing the reversing valve L1.
1 − Demand initiates at Y1 in the thermostat.
2 − 24VAC energizes compressor contactor K1.
3 − K1-1 N.O. closes, energizing compressor (B1) and out-
door fan motor (B4).
END OF COOLING DEMAND:
4 − Demand is satisfied. Terminal Y1 is de-energized.
5 − Compressor contactor K1 is de-energized.
6 − K1-1 opens and compressor (B1) and outdoor fan
motor (B4) are de-energized and stop immediate-
ly.
FIRST STAGE HEAT:
Internal thermostat wiring de−energizes terminal O by
heating mode selection, de−energizing the reversing valve
L1.
See steps 1, 2 and 3.
End of FIRST STAGE HEAT:
See steps 4, 5 and 6.
DEFROST MODE:
7 − During heating operation when outdoor coil temperature
drops below 42_(5.5_C)defrost switch (thermostat) S6
closes.
8 − Defrost control CMC1 begins timing. If defrost ther-
mostat (S6) remains closed at the end of the 30,60
or 90 minute period, defrost relay energizes and
defrost begins.
9 − During defrost CMC1 energizes the reversing valve and
W1 on the terminal strip (operating indoor unit on the
first stage heat mode), while de-energizing outdoor fan
motor B4.
10 − Defrost continues 14 + 1 minutes or until thermostat
switch (S6) opens. When defrost thermostat opens,
defrost control timer loses power and resets.
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