Lennox HP29 Series Unit Information page 28

a−HP29 Y", G", and J" Voltage Operation Sequence
This is the sequence of operation for HP29 Y" voltage.
HP29 G" and J" voltage units are similar, but have a few
additions. The G" voltage units have an outdoor fan relay,
while the J" voltage units have the outdoor fan relay plus
an outdoor fan transformer. The Y" voltage unit sequence
is outlined by numbered steps which correspond to circled
numbers on the adjacent diagram.
NOTE− The thermostat used may be electromechanical
or electronic.
NOTE− Transformer in indoor unit supplies power (24
VAC) to the thermostat and outdoor unit controls.
COOLING:
1 − Internal thermostat wiring
cooling mode selection, energizing the reversing valve
L1. Cooling demand initiates at Y1 in the thermostat.
2 − 24VAC energizes compressor contactor K1.
3 − K1-1 N.O. closes energizing compressor (B1) and
outdoor fan motor (B4).
4 − Compressor (B1) and outdoor fan motor (B4)
begin immediate operation.
END OF COOLING DEMAND:
5 − Cooling demand
de-energized.
6 − Compressor contactor K1 is de-energized.
7 − K1-1 opens and compressor (B1) and outdoor fan
motor (B4) are
immediately.
8 − Terminal O is de−energized when internal
thermostat wiring is out of cooling mode,
de−energizing reversing valve L1.
HP29 THREE-PHASE OPERATING SEQUENCE
energizes terminal O by
is satisfied. Terminal
de-energized and
FIRST STAGE HEAT:
9 − Heating demand initiates at Y1.
10 − 24VAC energizes compressor contactor K1.
11 − K1-1 N.O. closes energizing compressor and
outdoor fan motor.
12 − See step 4.
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.
DEFROST MODE:
16 − During
temperature drops below 35_F (2_C) or 42_(5.5_C)
(see defrost system description for specific unit dash
number) unit defrost switch (thermostat) S6 closes.
17 − Defrost control CMC1 begins timing. If defrost
thermostat (S6) remains closed at the end of the
30,60 or 90 minute period, defrost relay energizes
and defrost begins.
18 − During defrost CMC1 energizes the reversing valve
Y1 is
and W1 on the terminal strip (operating indoor unit on
the first stage heat mode), while de-energizing outdoor
fan motor B4.
19 − Defrost continues 14 + 1 minutes or until thermostat
stop
switch (S6) opens. When defrost thermostat opens,
defrost control timer loses power and resets.
20 − When CMC1 resets, the reversing valve and W1 on the
terminal strip are de-energized, while the outdoor fan
motor B4 is energized.
Page 28
heating operation when outdoor coil