Every year The Hartford Steam Boiler Inspection and Insurance Co. (HSB) investigates numerous small refrigeration unit failures. The primary reason for the majority of these failures is poor or non-existent preventive maintenance for the unit.

To help in achieving the reliable and uninterrupted service expected from refrigeration equipment, HSB offers the following recommendations.


One of the most critical controls in the refrigeration unit is the crankcase heater. These refrigeration units operate below the evaporator temperatures much of the year. Preferably, the heater should be left energized while the equipment is idle and be provided with indicator lights wired in series. The energized heater will minimize refrigerant migration foaming of the oils and the resulting immediate compressor failure. In all cases, it is vital that the crankcase heater be energized at least eight hours before starting the unit.


Because the operation and safety controls, including the expansion valve(s), are the heart of the unit, they should be checked annually to make certain they are properly calibrated and in good working order. Like all electrical and mechanical equipment, these controls wear out and must be checked regularly and replaced when they are determined to be unreliable.

The oil in the unit can also be tested at this time. The results of this analysis will let you know if the oil will hold up in the coming year. If there is any question about oil quality, the oil should be replaced.


• The motor magnetic starter should be checked annually.

• Contacts may be deteriorated as a result of cycling of the compressor.

• All terminal connections should be checked and tightened, and all pitted contacts should be replaced.

• The overload protection on the unit should be examined for proper sizing.


The unit’s condenser should be cleaned at a minimum of once each year. If the condenser is located in a high dust and dirt area, it should be scheduled for more frequent cleaning. A clean condenser will prevent high head pressure which can shorten the life of the unit.


The small refrigeration unit should be equipped with a moisture indicator to detect the presence of moisture within the system. If moisture is present, filter dryers should be installed or changed to remove the moisture. More importantly, the source of the moisture should be determined and preventive action taken to correct the condition. New refrigerants (post R-22), will attract moisture and can cause internal icing failures.


• The equipment owner should be aware that the cost of an unanticipated breakdown of a refrigeration unit can be expensive.

• Even when equipment insurance is available, the deductible may still account for a considerable expense.

• Because we are talking about refrigeration units, the owner must also consider spoilage of stored food.

• Visual/audible alarms should be installed which will indicate unacceptable changes in refrigerated space temperatures.

NOTE: This advice is intended to complement the equipment manufacturers’ recommendations — not replace them. If you have doubts about any particular procedure, contact your equipment service representative.

Reprinted courtesy of The Hartford Steam Boiler Inspection and Insurance Co. For more information, visit www.hsb.com.

Publication date: 7/6/2015

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