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SEQUENCE OF OPERATION HP29−090
After each thermostat demand, time delay locks
out the circuit to compressor contactor coil and
defrost control for 5 + 2 minutes. At the end of the
time period, the time delay allows the compressor
contactor and defrost control to be energized
upon demand.
COOLING
1 − Cooling demand energizes through terminal Y1 at the
indoor thermostat provided 5−minute time delay is sat
isfied.
2 − Voltage passes through N.C. K8−1 to CMCI defrost
control. K6 set coil is enegized.
3 − N.O. K6−1 latching relay contacts close, energizing L1
reversing valve.
4 − K58 low ambient relay is energized. N.C. K58−1 con
tacts open eliminating S11 by−pass.
5 − Voltage passes through S11 low pressure switch
(switch will close provided liquid line pressure rises to
275 + 10 psig.), energizing outdoor fan relay K10. N.O.
K10−1 contacts close, energizing outdoor fan B4. N.C.
K10−2 contacts open, de−energizing HR1 crankcase
heater.
6 − Compressor contactor K1 is energized. N.O. K1−1
contacts close, energizing compressor B1.
7− "G" from indoor thermostat sends 24V through K8−2
N.C. contacts to "G1" energizing indoor blower.
HEATING
1 − Heating demand energizes through terminal W1 at the
indoor thermostat provided 5−minute time delay is sat
isfied.
2 − K8 transfer relay is energized. N.C. K8−1 contacts
open and N.O. contacts close, sending voltage to
CMCI defrost control. K6 re−set coil is energized.
3 − N.O. K6−1 latching relay contacts open, de−energizing
L1 reversing valve.
4 − K58 low ambient relay is de−energized. N.C. K58−1
contacts close, by−passing S11 low ambient switch.
5 − K10 outdoor fan relay is energized. N.O. K10−1 con
tacts close, energizing outdoor fan B4. N.C. K10−2
contacts open, de−energizing HR1 crankcase heater.
6 − Compressor contactor K1 is energized. N.O. K1−1
contacts close, energizing compressor B1.
7 − K8−2 N.O. contacts close sending 24V from "G1" ener
gizing indoor blower.
DEFROST MODE
7 − During heating operation, when outdoor coil drops be
low 35 + 4_ F, the defrost thermostat S6 closes. When
S6 closes, K4 defrost relay is energized. If defrost ther
mostat remains closed at the end of 30, 60, or 90 min
utes, defrost control energizes and defrost begins.
8 − When defrost control energizes, reversing valve L1
and indoor heat relay are energized. Outdoor fan is de−
energized.
9 − Defrost continues until 14 + 1 minutes have elapsed or
until S46 defrost pressure switch opens. When defrost
pressure switch opens to terminate defrost, the defrost
timer loses power and resets. Defrost timing is
stopped until the next call for defrost (when defrost
thermostat closes).
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