All engine driven refrigeration compressors were intended to be used on
automobile air conditioning and not for medium to low temperature
refrigeration. In most cases if a compressor had a good service life in
an automobile it could work in a lower temperature system if the system
is designed correctly. If an engine drive refrigeration system is
designed and installed correctly the compressor will operate for twenty
plus years this is a proven fact. Engine driven systems designed by the
original companies of Crosby and Grunert were still running with the
same compressors, these were installed in the late 1970's.

There are a small percentage of new and rebuilt compressors that do
fail prematurely in the first twenty five hours but repeated compressor
failures are preventable. There are a number of reasons why the engine
driven compressor fail:

Compressor capacity is excessive for the size of holding plates; If a
compressor is putting out enough energy to freeze a 500 pound holding
plates in one hour and the plate only weighs 50 pounds the refrigerant
and oil return will not be adequate for lubrication or compressor
cooling, because the expansion device won't allow the flow. The
colder the plates are the less flow of needed refrigerant and oil.
Remember the compressor was designed for high back pressure
applications.

Too large an expansion valve for the evaporator coils in holding
plates; During the off cycle when holding plates are colder than
compressor refrigerant mixed with oil will migrate to the cold plates.
Then after start up with a large valve orifice there will be a quick
flood of this liquid mixture flooding back to compressor causing stress
on reed valves and connecting rods. Some systems must have suction line
accumulators to reduce the liquid return to an acceptable level.

Improper type of refrigerant and oil; Most engine driven refrigeration
systems violate the basic principles of refrigeration, Condensing unit
and return line along with evaporator should be designed to allow
gravity to assist in liquid return, Each component in the system must
be able to match the capacity of the compressor. Oil return will
always depend on miscibility in our boat refrigeration systems, R12 and
mineral oil are miscible, 134a or R12 and polyester oil are miscible
all other refrigerants lack different levels of miscibility at low
temperatures.

Too large of a line in holding plate or anywhere in low pressure side
of system will cause oil accumulation and compressor oil starvation.

Too small of a line or restriction in low pressure side of system will
cause oil accumulation in lines and very low compressor suction
pressure.