Marine Refrigeration – Essential Knowledge

What type of refrigerant gases do marine refrigeration systems use?

The well known gases R22 and R12 have been phased out due to the CFC effects on the ozone layer. This has been driven also by the 1990 Clean Air Act amendments. As a result the industry has had to come up with new refrigerant gases that comply with this. There have been some 12 new refrigerants and 4 different types of oils. This means that you have to exercise caution as any mismatch will substantially affect the system performance and reliability or even destroy the marine refrigeration system.

The main refrigerant gas being used is HFC-134a, which is also known as R134. There are now standards labeling, service equipment and service connectors to reduce the chances of mixing systems and the adverse results of oil and gas cross-contamination.

While industry has implemented these measures boat and marine refrigeration systems tend to lag, and systems should be clearly labeled with the type of oil and viscosity as well as the type of refrigerant used within the system.

Marine Refrigeration Refrigerant Oils

1. Mineral Oils. The mineral oil is a wax free oil that has been used as a standard for refrigeration. When mineral oil it is mixed with Freon 12 and circulates through the entire system. Mineral oil does not mix with R134a refrigerant gas.

2. Alkylbenzene refrigerant oil is a synthetic aromatic hydro-carbon. This oil is compatible with mineral oil and has improved oil return characteristics over that of mineral oil. It may be used with most refrigerant gases but not with 134a. It should be noted that most new low temperature AC hermetic compressors use Alkylbenzene oil.

3. Polyol Ester oil must be used with R134a refrigerant. This oil is also compatible and acceptable for use with R12, R22, and 502. The majority of engine driven marine refrigeration systems use this oil.


Compressor Fails to Start

1. Power supply failed or tripped

2. Motor overload device (bridge & check)

3. Relay defective

4. Compressor fault

5. Thermostat fault (bridge out same and re-check)

6. Connection fault

7. Motor Capacitor failure

Compressor Fails to Start (Makes humming sound)

1. Low voltage to compressor motor

2. Start relay faulty

3. Compressor internal fault

4. Defective start capacitor

5. Motor winding fault

Compressor Trips Overload

1. Low voltage to compressor motor

2. Motor winding fault

3. Compressor seizing

4. Start relay not opening

Compressor Runs Continuously

1. Low refrigerant charge

2. Refrigerant leak

3. Thermostat fault

4. Condenser is dirty

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