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VII-WIRING DIAGRAMS AND SEQUENCE OF OPERATIONS
A- CBA27UHE Units 208/230V/460V SINGLE PHASE - SEQUENCE OF OPERATION
1- Line voltage is routed to transformer T1 and blower
motor B3.
2- T1 supplies 24VAC to terminal strip TB1, which sup
plies 24VAC to the indoor thermostat and electric heat,
if used.
HEATING
3- When there is a call for heat, W1 of the thermostat ener
gizes the electric heat relay K32 (covered in the electric
heat section).
4- Blower motor B3 is energized on heating speed after
K20-1 closes.
5- Economizer (if used) is energized.
SINGLE-STAGE COOLING (Y1 to Y2 jumper in place)
6- When there is a call for cooling, Y2 of the thermostat ener
gizes blower on cooling speed.
TWO-STAGE THERMOSTAT
(remove jumper between Y1 and Y2)
FIRST-STAGE COOLING
7- When there is a call for cooling, Y1 sends power through
the room thermostat to G to energizes blower on first stage
cooling speed.
SECOND-STAGE COOLING
8- When there is a call for second stage cooling, Y2 of the
thermostat energizes blower on cooling speed.
1
2
3
4
6
5
1
208/230V - Single Phase
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