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Compressor Description
General Description
The most significant part of the refrigeration
system is the compressor. Its function is to pump
low pressure gas out of the evaporator so that a
rapid and continuous boiling action is maintained
in the evaporator coil. The low pressure gas is
compressed and forced into the condenser coil
where it is cooled by air passing through the coil.
The high pressure and reduced temperature causes
it to liquefy (condense).
The compressors covered by this manual are
reciprocating piston type pumps, constructed
mainly of cast aluminum. The aluminum alloy
pistons and cast iron sleeves are machined to close
tolerances to that no rings are needed to seal the
piston to the cylinder wall. The compressor is
equipped with a high nickel alloy ductile iron
crankshaft. To prevent leakage around the
crankshaft, the compressor is fitted with a rotary
type refrigeration seal.
Pressurized lubrication is provided to the
connecting rods and bearings by a gerotor oil
pump in the compressor body. The oil level in the
compressor can be inspected through the oil level
sight glass in the body. Since the refrigeration
system is sealed, it should be necessary to add oil
only if there has been a large refrigeration leak in
the system, or if a major item in the refrigeration
system, such as an evaporator coil or a condenser
coil has been replaced.
A spring loaded discharge valve and spring loaded
valve cage provide pressure relief if liquid
refrigerant enters the compressor. The entire cage
lifts and prevents breaking or deforming of the
valves.
When any repairs or replacements are to be made
on the compressor, it is very important that the
parts used are clean and not nicked or scratched.
During disassembly, parts should be cleaned and
inspected; and if they are to be used in
reassembly, they should be wrapped in a clean
cloth to prevent marring the surfaces. Oil all parts
with compressor oil during assembly, and be sure
they are installed in the same position they were
in before disassembly.
NOTE: When replacement parts are required,
we recommend using only Factory Approved
Thermo King Replacement Parts. Only Genuine
Thermo King Replacement Parts deliver the
reliability, productivity, quality, and performance
you’ve come to expect from Thermo King.
NOTE: Most of the overhaul procedures for the
compressors covered in this manual are the
same. Photographs of an X426 compressor are
used in this manual as examples. Other
illustrations are provided in cases where the
photograph is not applicable.
Compressor Model
Identification
There are a number of compressor models. The
following information is provided to help identify
the different compressor models. Refer to the
appropriate Parts Manual to order the correct
parts.
Two Cylinder Compressors
The one basic model of the two cylinder
compressor is the X214. There are some minor
variations such as fittings and oil sumps, but
otherwise all X214 compressors are basically the
same.
Four Cylinder Compressors
There are four major differences in the four
cylinder compressors:
•
The crankshaft drive shaft diameter is either
1.0 in. (small shaft), or 1.187 in. (large shaft).
•
The crankshaft drive end bearing is either a C3
bearing, or a C5 bearing.
•
A pressurized seal cavity was phased into use
on large shaft compressors starting in the first
quarter of 2014.
•
An internal oil filter were phased into use on
large and small shaft compressors in truck and
trailer units that typically use compressors
with an external oil filter starting in the first
quarter of 2014.
