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SERVICE HANDBOOK
Operation
Crankcase Heater Prevents Liquid Migration
This sequence (see Figures 6-6 and 6-7) shows the effects of an electric strap-on crank-
case heater applied to the compressor (also see Figure 6-5). The system was again shut-
down for a weekend under identical conditions with the exception that the heater was
energized throughout the shutdown period. By raising the temperature of the oil, we have
reduced its ability to attract and hold refrigerant.
Note that liquid refrigerant accumulation in the compressor can also be caused by liquid
floodback under certain conditions while operating. This condition can be controlled by
the application of a suction line accumulator. Crankcase heat does nothing to prevent
liquid floodback and an accumulator does nothing to prevent refrigerant migration. Each
without the other is half a job. Both together provide balanced compressor protection.
Compressor
Crankcase
Heater
When applied to a compressor with
a low pressure housing, an electric
strap-on crankcase heater prevents
liquid migration.
FIGURE 6-5:
View through sight glass shows that
the crankcase heater effectively
prevents migration of liquid
refrigerant to the compressor.
FIGURE 6-6:
Normal run with heat. Oil level
is maintained thereby assuring
effective lubrication for compressor
bearings.
FIGURE 6-7:
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