Three-Phase Cooling Sequence - Lennox HP21 Unit Information

9 4
1
6
7 2
J−THREE-PHASE COOLING SEQUENCE
1− 1st stage cooling demand energizes TB15-Y1 and TB15-O. TB15-O
energizes reversing valve L1. TB15-Y1 energizes TSC terminal
JP44-6, relay K10 and defrost control terminal HOLD. Defrost control
monitors liquid line temperature and turns off defrost control when liq-
°
uid line rises above 65 F.
NOTE-2nd stage cooling demand may be energized directly without
passing through 1st stage.
2− Relay contacts K10-1 switch to energize the outdoor fan and to de-en-
ergize the crankcase heater.
3− TSC delays 3 seconds before responding to the new command.
4− If the unit is changing from 2nd stage to 1st stage demand, TSC initi-
ates speed change delay and de-energizes JP44-8 and JP44-9 to stop
all unit operation for 60+5 seconds. Outdoor fan continues to operate.
After TSC completes the 60+5 second speed change delay or if the unit
is starting-up in 1st stage directly from OFF mode, TSC checks safety
circuits by looking for 24VAC at JP44-7 and by checking resistance
through wires connected to S1 and S2.
5− If all safety circuits check-out, TSC energizes K1 and compressor be-
gins low speed startup.
3
5
10
FIGURE 35
Page 37
8 11
1
6− 2nd stage cooling demand energizes TB15-Y1, TB15-Y2 and TB15-O.
TB15-Y2 energizes TSC terminal JP44-4. TB15-Y1 energizes TSC
terminal JP44-6, defrost control terminal HOLD and outdoor fan relay
K10.
7− Relay contacts K10-1 switch to energize the outdoor fan and to de-en-
ergize the crankcase heater.
8− TSC delays 3 seconds before responding.
9− If the unit is changing from 1st stage to 2nd stage demand, the TSC
initiates speed change delay and de-energizes JP44-8 and JP44-9 to
stop all unit operation for 60+5 seconds. After TSC completes the 60+5
second speed change delay or if the unit is starting-up in 2nd stage di-
rectly from OFF mode, TSC checks safety circuits by looking for
24VAC at JP44-7 and by checking resistance through wires connected
to S1 and S2.
10− If all safety circuits check-out, TSC energizes K69. Compressor be-
gins high speed startup.
11− When thermostat demand is satisfied or if thermostat is switched OFF
or switched to heating mode, all outdoor unit operation stops after a
delay of 3 seconds. TSC then completely resets (erase accumulated
faults) before beginning a 5 minute timed-off delay.
S1, S2 DENOTE
TERMINAL DES-
IGNATIONS