Three-Phase Compressor Startup - Lennox HP21 Unit Information

5
1
3
1
FIGURE 34
6
2
7
8
4
I−THREE-PHASE COMPRESSOR STARTUP
1− Low speed demand energizes outdoor fan relay K10 and JP44−6.
K10-1 switches to energize the outdoor fan and de-energize the crank-
case heater. Outdoor fan begins operating immediately.
2− After appropriate time delay and if all safety circuits check out, TSC
energizes JP44-9. Contactor K1 is energized through K69-2 N.C. con-
tacts.
3− K1 N.O. contacts close to begin compressor low speed startup. K1
N.C. contacts open to disconnect the high speed wiring circuitry.
4− Compressor B1 terminal 1 is energized by K1 contacts L1-T1. Com-
pressor terminal 2 is energized by contactor K1 terminal L2-T2.
Compressor terminal 3 is energized by contactor K1 terminal L3-T3.
This arrangement forms a series DELTA connection to the motor wind-
ings for low speed.
5− High speed demand energizes JP44-4.
6− After appropriate time delay and if all safety circuits check out, TSC en-
ergizes JP44-8.
7− When contactor K1 is de-energized, contacts K1-1 normally closed
contacts form a parallel DELTA connection to the motor windings for
high speed.
8− Contactor K69 energizes through K1-2 N.C. contacts (speed change
delay has reset K1-2 to N.C. position). N.O. K69-1 contacts close to be-
gin compressor high speed startup.
energized by contactor K69 terminal L1-T1. Compressor terminal 6 is
energized by contactor K69 terminal L2-T2. Compressor terminal 5 is
energized by contactor K69 terminal L3-T3.
Page 36
LOW SPEED
HIGH SPEED
Compressor terminal 4 is