reverses until the contacts are separated at a pre-
determined low-suction pressure, thus breaking the
motor controller circuit and stopping the compressor.
SUCTION LINE FILTER-DRIER.Some
systems include a low-side filter-drier (fig. 6-31) at the
compressor end of the suction line. The filter-drier
used in the suction line should offer little resistance to
flow of the vaporized refrigerant, as the pressure
difference between the pressure in the evaporator and
the inlet of the compressor should be small. These
filter-driers function to remove dirt, scale, and
moisture from the refrigerant before it enters the
GAUGES AND THERMOMETERS.
Between the suction line stop valve and the
compressor, a pressure gauge and thermometer may be
provided to show the suction conditions at which the
compressor is operating. The thermometer shows a
h i g h e r t e m p e r a t u r e t h a n t h e t e m p e r a t u r e
corresponding to the suction pressure indicated on the
gauge, because the refrigerant vapor is superheated
during its passage from the evaporator to the
ACCUMULATORS AND OIL SEPARA-
TORS.Liquid refrigerant must never be allowed to
enter the compressor. Liquids are noncompressible; in
other words, their volume remains the same when
compressed. An accumulator (fig. 6-32) is a small tank
accessory; that is, a safety device designed to prevent
liquid refrigerant from flowing into the suction line
and into the compressor. A typical accumulator has an
Figure 6-30.Pressure type cut-in, cutout control switch.
Figure 6-31.A suction line filter-drier.
outlet at the top. Any liquid refrigerant that flows into
the accumulator is evaporated, and then the vapor will
flow into the suction line to the compressor.
Oil from the compressor must not move into the
rest of the refrigeration system. Oil in the lines and
evaporator reduces the efficiency of the system. An oil
separator (fig. 6-33) is located between the compressor
discharge and the inlet of the condenser. The oil
separator consists of a tank or cylinder with a series of
baffles and screens, which collect the oil. This oil
settles to the bottom of the separator. A float
arrangement operates a needle valve, which opens a
return line to the compressor crankcase.
What are the three types of compressors used in
What is the difference between the internal and
external bellows crankshaft seal?
What are the two drawbacks of a hermetic
What are the two primary types of evaporators?
A capillary tube-metering device is most
commonly used on what type of refrigeration
What is the function of a sight-flow indicator?
Learning Objective: Understand and identify
classification of common refrigerants and their
application. Understand the requirements for ozone
protection and the Clean Air Act.
Figure 6-32.Accumulator location.