A LOOK AT SERVICE SAFETY
Operation
115
IV.
Control of Liquid Refrigerant
Floodback to the Compressor
During Operation
Liquid floodback during operation (see Figure 6-9)
can be caused by fan failure or dirty clogged filters
that can reduce the heat transfer rate to such a point
that the liquid refrigerant floods through, instead of
vaporizing. When this situation occurs, liquid
refrigerant may enter the compressor under condi-
tions which result in separation of the oil and refrig-
erant. This separation may result in an
accumulation of the refrigerant under the oil (see
Figure 6-10). Thus, when the compressor is started,
the first liquid to be pumped to the bearings will
probably be refrigerant, not oil. Even if this oil-
refrigerant separation does not occur, the large
amount of liquid refrigerant in the crankcase will
instantly vaporize and boil away the oil charge when
the compressor starts (see Figure 6-11). Thereby
leaving the compressor oil-starved for many seconds
(see Figure 6-12).
Figure 6-9.
Liquid refrigerant floodback to the compressor.
High Pressure Gas
High Pressure Liquid
Low Pressure Liquid
Low Pressure Gas
Fan
Fan
Evaporator
Condenser
Compressor
Expansion Device
Filter
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