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ZCC092/150 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 - Indoor thermostat terminal G energizes blower relay
1st Stage Cooling (compressor B1 low capacity)
3 -
by the thermostat. G energizes blower. 24VAC is
routed through TB1 passing N.C. high pressure
switch S4. Compressor contactor K1 is energized.
N.O. contacts K1 close energizing B1 two-step
4 - Optional N.O. low ambient switch S11 closes to
energize condenser fan relay K10. N.O. contacts
K10-1 and K10-2 close energizing condenser fans
2nd Stage Cooling (compressor B2 is energized)
Second stage cooling demand 24VAC is routed
through TB1 and proves N.C. high pressure switch
S7. Compressor contactor K2 is energized. N.O.
K2 contacts close energizing compressor B2. In
6 - Optional N.O. low ambient switch S84 closes to
energizing condenser fan relay K10. N.O. contacts
K10-1 and K10-2 close energizing condenser fans
3rd Stage Cooling (compressor B1 High Capacity)
7 -
through TB1 and energizes N.O. contacts on K36
High Speed or 60Hz.
8 -
through TB1 and energizes L34 2-Stage Solenoid
for Compressor B1. Compressor B1 is now
operating at high-capacity.
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