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CAPACITY CONTROL MODIFICATIONS FOR HEAT
PUMP APPLICATION — Where 5F40, 5F60, and 5H com-
pressors are used in refrigerant cycle reversing heat pump
applications, it is usually necessary to modify the standard
capacity control arrangement to satisfy unloading require-
ments. On summer cycle, the compressor is required to unload
as circulating water or air temperature drops. During winter
cycle, the control works in reverse, so that the compressor
unloads as the circulating water or air temperature increases. It
is necessary for the compressor to unload in response to either
a summer or winter temperature-sensing device, depending on
the particular cycle in operation.
Where summer and winter design suction temperatures are
within design range of either electric or pneumatic compensa-
tion devices, capacity control may be external. However,
another means is normally required.
Usually modification to the compressor capacity control
system is required. The compressor can be modified in 2 ways:
(1) for applications requiring 50% capacity reduction; (2) for
applications requiring more than one step of capacity reduc-
tion. See Fig. 10 for a typical 2-step external capacity control
arrangement.
UNLOADER PUMP
TO CRANKCASE
(CONNECTION ON
PUMP END COVER)
SEE FIG. 15
OIL TO UNLOADER
1/4 NPT (FOUR PLACES)
PUMP END BEARING HEAD
2
4
*STEP #2 IS OMITTED ON 5H40 COMPRESSOR
3
3/8 NPT
3-WAY SOLENOID VALVE
SEE FIG. 13
PUMP OIL
PRESSURE
4
3
2
1
*
1/4 NPT
1
Fig. 14 — 5H40, 46, 60, 66, 80, 86 Bearing Head
TO DUMP CONTROL OIL BACK INTO OIL RESERVOIR USE
EITHER CONNECTION
1/4”-18 NPT
5/8”-18 NF
Fig. 15 — 5H40, 46, 60, 66, 80, 86
Pump End Cover Assembly