Specifications

18
15.4 HIGH AND LOW PRESSURE CONTROLS (HPC & LPC)
These controls keep the compressor from operating in pressure ranges which can
cause damage to the compressor. Both controls are in the low voltage control cir-
cuit.
High pressure control (HPC) is an auto-reset which opens near 610 PSIG and
closes at 420 PSIG.
The low pressure control (LPC) is an automatic reset which opens near 50 PSIG
and closes near 95 PSIG.
16.0 SERVICE
16.1 OPERATION
Single phase units are operated PSC (no starting components). It is important that
such systems be off for a minimum of 5 minutes before restarting to allow equaliza-
tion of pressure. The thermostat should not be moved to cycle unit without waiting 5
minutes. To do so may cause the compressor to go off on an automatic overload
device or blow a fuse. Poor electrical service can also cause nuisance tripping on
overloads, trip a breaker, or cause light dimming. This generally can be corrected
by adding start components. Check with factory for recommended start compo-
nents, if required. For PSC type operation, refrigerant metering must be done with
fixed orifice, cap tubes or bleed type expansion valves because of low starting
torque. If non-bleed expansion valve coils (supplied by factory) are used, start com-
ponents are required.
16.2 SINGLE-POLE COMPRESSOR CONTACTOR (CC)
Single-pole contactors are used on all standard single phase units up through 5
tons. Caution must be exercised when servicing as only one leg of the power sup-
ply is broken with the contactor.
FIGURE 2
CONTROL WIRING FOR GAS OR OIL FURNACE
FOR TYPICAL ELECTRIC HEAT
FOR TYPICAL GAS OR OIL HEAT
C
Y
G
W
R
W/BL
R
W/BK
G/BK
YL
BR
PU
YG
W
R
TYPICAL THERMOSTAT
SUBBASE
TYPICAL GAS OR
OIL FURNACE
TYPICAL CONDENSING
UNIT
BR – BROWN WIRE
YL – YELLOW WIRE
X–WIRE CONNECTION
BR – BROWN WIRE
R–RED WIRE
YL – YELLOW WIRE
W/BK – WHITE WIRE WITH BLACK STRIPE
G/BK – GREEN WIRE WITH BLACK STRIPE
PU – PURPLE WIRE (NOT USED)
X – WIRE CONNECTION
*
IF MAXIMUM OUTLET TEMPERATURE RISE IS DESIRED, IT IS RECOMMENDED THAT
W1 (W/BK) AND W2 (W/BL) BE JUMPERED TOGETHER.
YL
BR
TYPICAL CONDENSING
UNIT
YL
BR
X
X
X
X
X
X
X
X
X
YG
W
R
TYPICAL THERMOSTAT
SUBBASE
X
TYPICAL ELECTRIC HEAT
LOW VOLTAGE JUNCTION BOX
•
*