Three-Phase Starting Sequence - Lennox HP21 Unit Information

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H−THREE-PHASE STARTING SEQUENCE
1− Line voltage feeds through L1, L2 and L3 to energize outdoor trans-
former T19 and outdoor unit. Crankcase heater is energized through
relay K10-1 outdoor fan contacts.
2− Transformer T19 provides 24VAC to TSC and contactors K1 and K69.
3− The indoor transformer supplies 24VAC to the indoor unit and the in-
door thermostat. Indoor transformer also provides 24VAC power to
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FIGURE 33
defrost control CMC1, reversing valve L1, outdoor fan relay K10,
speed control thermostat S55, service light thermostat S54 and ambi-
ent thermistor RT3 in outdoor unit.
4− On power-up, 24VAC is fed through JP44-1 and JP44-7 to the TSC.
The TSC begins a 10 second power-up delay.
5− The TSC begins a 5 minute delay during which the outdoor unit is not
operational. After the 5 minute delay, the TSC waits in OFF" mode for
1st stage or 2nd stage demand.
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S1, S2 DENOTE
TERMINAL
DESIGNATIONS