Commercial Cooler Repair & Service

Walk in Commercial cooler operation. Knowing how your walk in cooler works will save you money and frustration. Some walk in commercial Cooler equipment problems are caused by not understanding the operation.

Your Commercial Walk in cooler cooler is very similar to a commercial reach-in cooler. It is not similar to a residential refrigerator. A household refrigerator is actually a freezer that uses some of the freezer’s air to cool the refrigerator part.


A walk in cooler in moves heat from the box to the space around the condenser outside. In addition typical temperature ranges are from 35 degrees Fahrenheit to 41 degrees. Below 35 degrees a forced defrost cycle is needed to avoid freeze ups.However a walk in cooler uses warm air defrost. This is how a cooler works. This example will use a box that has a thermostat that is set at 40 degrees with a 5 degree differential.

The Thermostat Calls for Cooling

The temperature in the commercial cooler has risen to the set point of 40 degrees. The thermostat closes and the compressor and condenser fan comes on. In addition the condenser fan may cycle on and off in cold ambient temperatures. The evaporator fans blow cold air into the cooler. The air circulates around the box absorbing heat. After that the warmed air is pulled into the back of the evaporator. The heat is removed from the air as it passes through the evaporator.

The evaporator fan continues to run as the temperature drops to 35 degrees. In addition there maybe light frost build up on the evaporator. This is normal, since the coil in the evaporator is about 10 degrees colder than the 35 degree air entering it.

Thermostat Operation

The Thermostat is Satisfied
When the temperature in the walk in cooler  reaches 35 degrees inside (40 degree set point minus 5 degree differential), the thermostat cuts the compressor and the condenser fan motor off. However after that the evaporator fans continue to run. In addition the fans in the walk in cooler  should always be running.

Heat is absorbed through the walls of the cooler, from door openings and from the product. Therefore the temperature continues to rise. Any frost that was built up on the evaporator will melt now. In addition the air needs to be at least 35 degrees for dependable defrost.

This is an important point. Above all if the walk in does not shut off at the set point temperature, the compressor will not cut off and evaporator can not defrost. This can be caused by the thermostat being set too low or failing. After that liquid refrigerant can make it back to the compressor and cause compressor failure.

The air in the walk in cooler continues to warm until it reaches 40 degrees. After that the thermostat calls for cooling again.

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