Sequence of Operation
Power:
1 - Line voltage from unit disconnect energizes
transformer T1. T1 provides 24VAC power to
terminal strip TB1. TB1 provides 24VAC to the unit
Blower Operation:
2 -
Economizer Operation:
3 - The economizer control module receives a demand
4 -
exhaust fan motor B10.
1st Stage Cooling (compressor B1)
by the thermostat. G energizes blower. 24VAC is
routed through TB1 passing N.C. freezestat S49 and
optional N.C. high pressure switch S4. Compressor
contactor K1 is energized. N.O. contacts K1-1 close
energizing compressor B1. N.C. Contacts K1-2
6 - Contacts K10-1 close energizing condenser fan B4.
2nd Stage Cooling (compressor B2)
7 - 24VAC is routed through TB1 and proves N.C.
switch S7. Compressor contactor K2 is energized.
N.O. K2 contacts close energizing compressor B2.
N.C.K2-2 opens de-energizing crankcase heater
8 - N.O. contacts K10-1 close energizing condenser
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