Lennox 14HPX Unit Information page 24

This is the sequence of operation for 14HPX series
units. The sequence is outlined by numbered steps
which correspond to circled numbers on the adjacent
diagram. The steps are identical for both cooling and
first stage heating demand with the exception revers-
ing valve L1 is energized during cooling demand and
de−energized during heating demand.
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.
14HPX OPERATING SEQUENCE
FIRST STAGE HEAT:
End of FIRST STAGE HEAT:
DEFROST MODE:
Page 24
Internal thermostat wiring de−energizes terminal O by
heating mode selection, de−energizing the reversing valve
L1.
See steps 1, 2 and 3.
See steps 4, 5 and 6.
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 90°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.