Basic Refrigeration - Control Of Liquid Refrigerant Floodback - True GDM Series Technical & Service Manual

CFC & REFRIGERATION BASICS
BASIC REFRIGERATION
Control of Liquid Refrigerant Floodback To The Compressor During Operation
Evaporator
Compressor
LOW PRESSURE HIGH PRESSURE
GAS GAS
Evaporator
Accumulator
Crankcase
Heater
Compressor
LOW PRESSURE HIGH PRESSURE
GAS GAS
LIQUID REFRIGERANT ACCUMULATION IN THE COMPRESSOR CAN ALSO BE CAUSED BY
LIQUID MIGRATION TO THE COMPRESSOR DURING PERIODS OF SHUTDOWN. THIS CONDI-
TION CAN BE CONTROLLED BY THE APPLICATION OF A CRANKCASE HEATER. A SUCTION
LINE ACCUMULATOR DOES NOTHING TO PREVENT LIQUID MIGRATION AND A CRANKCASE
HEATER DOES NOTHING TO PREVENT LIQUID FLOODBACK. EACH WITHOUT THE OTHER
IS HALF A JOB - BOTH TOGETHER PROVIDE BALANCED COMPRESSOR PROTECTION.
Fan Fan
Filter
Condenser
Expansion Device
LOW PRESSURE HIGH PRESSURE
LIQUID LIQUID
Fan Fan
Filter
Condenser
Expansion Device
LOW PRESSURE HIGH PRESSURE
LIQUID LIQUID
Liquid floodback during operation 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
conditions which result in separation of the oil and refrig-
erant. This separation may result in an accumulation of the
refrigerant under the oil. 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 refrig-
erant in the crankcase will instantly vaporize and boil away
the oil charge when the compressor starts. Thereby leaving
the compressor oil-starved for many seconds.
Liquid floodback can be prevented by the application of a
properly designed and sized suction line accumulator.
Using a totally new concept, Tecumseh engineers have
designed a suction line accumulator available in eight basic
sizes covering a full range of system applications and
refrigerant. When properly selected based upon system
c h a rge, a Tecumseh suction line accumulator will improve
compressor reliability and endurance by preventing dam-
aging liquid refrigerant floodback.
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