112
Chapter 6
B. Crankcase Heater Prevents Liquid
Migration
This sequence (see Figures 6-6 and 6-7) shows the
effects of an electric strap-on crankcase heater
applied to the compressor (also see Figure 6-5). The
system was again shutdown for a week-end 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 con-
dition can be controlled by the application of a suc-
tion 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 pro-
vided balanced compressor protection.
Figure 6-5.
When applied to a compressor with a
low pressure housing, an electric
strap-on crankcase heater prevents
liquid migration.
Compressor
Crankcase
Heater
Figure 6-6.
View through sight glass shows that
the crankcase heater effectively
prevents migration of liquid refrigerant
to the compressor.
Figure 6-7.
Normal run with heat. Oil level is
maintained thereby assuring effective
lubrication for compressor bearings.
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