Single-Phase Cooling Sequence - Lennox HP21 Unit Information

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E−SINGLE-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 and defrost control terminal HOLD. Defrost control begins ini-
tial timing sequence.
NOTE-2nd stage cooling demand may be energized directly without
passing through 1st stage.
2− TSC delays 3 seconds before responding to the new command.
3− 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. After TSC completes the 60+5 sec-
ond 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.
4− If all safety circuits check-out, TSC energizes K1 and compressor be-
gins low speed startup.
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FIGURE 30
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5− 2nd stage cooling demand energizes TB15-Y1, TB15-Y2 and TB15-O.
TB15-O energizes TSC terminal JP44-4. TB15-O energizes TSC ter-
minal JP44-6 and defrost control terminal HOLD.
6− TSC delays 3 seconds before responding.
7− 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.
8− If all safety circuits check-out, TSC energizes K1 and K69. Compres-
sor begins high speed startup.
9− 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.
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