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When CFC or HCFC refrigerants are used with mineral or
alkylbenzene oils, foam in the sight glass normally indicates
either that there is serious liquid refrigerant floodback or
that the running gear is hitting the oil due to a very high oil
level. Very high oil levels are caused by either too much oil
or excessive liquid refrigerant in the crankcase. HFC refrig-
erants and POE oils do not foam easily, so there will be less
indication in the sight glass of either liquid refrigerant flood-
back or too much oil in the system.
NOTE: One possible cause of flooding is improper control
of the defrost cycle. Ensure defrost cycles are staggered so
no more than one third of the system is on defrost at any
time.
COMPRESSOR OPERATING LIMITS
Figures 1A and 1B show the components and typical operat-
ing ranges of the Carlyle 06D, E, and 06CC compressors.
CAUTION
Liquid refrigerant should never be allowed to flood back to
the compressor. It may wash out bearings and damage gas-
kets. If liquid floodback is occurring, adjust the expansion
valve or make other adjustments as necessary to eliminate
this condition.
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