Page 25
SEQUENCE OF OPERATION HP29−120
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.
2 − Voltage passes through N.C. K8−1 to CMCI defrost
control. K6 set coil is energized.
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, eleminating the S11 and S41 by−pass.
5 − Voltage passes through S11 low pressure switch,
(switch will close provided liquid line pressure rises to
275 + 10 psig.), energizing K10 outdoor fan relay 1.
N.O. K10−1 contacts close, energizing outdoor fan B4.
N.C. K10−2 contacts open de−energizing HR1 crank
case heater.
6 − Voltage passes through S41 low ambient switch ener
gizing K68 outdoor fan relay 2. N.O. K68−1 contacts
close, energizing outdoor fan B5.
7 − Compressor contactor K1 is energized. N.O. K1−1
contacts close, energizing compressor B1.
8 − "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.
2 − K8 transfer relay is energized. N.C. K8−1 contacts
open and N.O. contacts close, sending voltage to
CMCI defrost control. K6 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 and
S41 low ambient thermostat.
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 − Voltage passes through S41 low ambient switch
(switch will close provided ambient is high enough),
energizing K68 outdoor fan relay 2. N.O. K68−1 con
tacts close energizing outdoor fan B5.
7 − Compressor contactor K1 is energized. N.O. K1−1
contacts close energizing compressor B1.
8 − K8−2 N.O. contacts close sending 24V from "G1" ener
gizing indoor blower.
DEFROST MODE
8 − During heating operation, when outdoor coil drops be
low 35 + 4_ F, defrost thermostats S6 (circuit 1) and
S124 (circuit 2) close. When S6 or S124 close, K4 de
frost relay is energized. If defrost thermostat remains
closed at the end of 30, 60, or 90 minutes, defrost con
trol energizes and defrost begins.
9 − When defrost control energizes, reversing valve L1
and indoor heat relay are energized. Outdoor fan is de−
energized.
10− Defrost continues until 14 + 1 minutes have elapsed,
or until S46 defrost pressure switch opens. When de
frost 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).
To Next Page
Loading...
Need help?
General
