Lennox KHA SERIES, Руководство пользователя

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Page 43
SEQUENCE OF OPERATION KHA024/060
Power:
1. Line voltage from unit disconnect energizes transform-
er T1. T1 provides 24VAC power to terminal strip TB1
found in the control box. TB1 provides 24VAC to the
unit cooling, heating and blower controls.
Blower Operation:
2. Indoor thermostat terminal G" energizes contactor K3.
K3 closes, energizing blower B3.
Economizer Operation:
3. The EXH (power exhaust set point) found on the face of
A6, is factory set at approximate 50% of the dial range.
Economizer control module A6 receives a demand and
opens outside dampers 50%. Power exhaust fan relay
K65 is energized 30 seconds after dampers are 50%
open. K65−1 and K65−2 close, energizing power ex-
haust fan B10.
Cooling Demand
Cooling demand energizes Y1 and G in the thermostat. G
energizes blower (see step 2.)
4. Indoor thermostat COOLING mode energizes reversing
valve L1.
5. CMC1 proves N.C. freezestat S49 and optional N.C. high
pressure switch S4 to energize compressor contactor K1.
6. K1 closes energizing compressor B1.
7. P and Y Voltage
Line voltage is routed through optional N.O. low ambient
pressure switch S11 and optional low ambient kit K58 to
energize outdoor fan B4.
G, J and M Voltage
24VAC passes through optional N.O. low pressure switch
S11 and optional low ambient kit K58 to energize outdoor
fan relay K10. N.O. contacts K10−1 close energizing out-
door fan B4 .
First Stage Heat
NOTE: On heating demand after unit has been in cool-
ing mode, indoor thermostat in HEATING mode will de−
energize reversing valve L1.
8. Heating demand energizes W1 in the thermostat. Relay
K8 is energized. N.C. K8−1 opens, de−energizing revers-
ing valve L1.
9. CMC1 proves N.C.high pressure switches S4 and N.C.
freezestats S49 . Compressor contactor K1 is energized.
10. K1 closes energizing compressor B1.
11.
P and Y Voltage
Line voltage from CMC1 is routed through optional N.C.
low ambient switch S11 to energize outdoor fan B4.
G, J and M Voltage
24VAC passes through optional N.O. low pressure switch
and optional low ambient switch K58 to energize outdoor
fan relay K10. K10−1 closes energizing outdoor fan B4.
Second Stage Heat (electric heat):
12. Second stage heat demand energizes W2 in the thermo-
stat.
See sequence of operation for electric heat.
Defrost Mode:
DEFROST MODE:
13. When a defrost cycle is initiated, the control ener-
gizes the reversing valve solenoid and turns off the
condenser fan. The control will also put 24VAC on
the W1" (auxiliary heat) line. The unit will stay in this
mode until either the defrost thermostat (S6) tem-
perature is above the termination temperature of
70°, the defrost time of 14 minutes has been com-
pleted, or the room thermostat demand cycle has
been satisfied. If the room thermostat demand cycle
terminates the cycle, the defrost cycle will be held
until the next room thermostat demand cycle. If the
defrost thermostat (S6) temperature is still below
the termination temperature, the control will contin-
ue the defrost cycle until the cycle is terminated in
one of the methods mentioned above.