Understanding Your Walk In Cooler

Understanding your walk in cooler will save you money and frustration. Many refrigeration problems are caused by not understanding the operation of commercial refrigeration equipment.

Your walk in refrigerator is very similar to a commercial reach-in refrigerator. 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 moves heat from the box to the space around the condenser. Typical temperature ranges are from 35 degrees Fahrenheit to 41 degrees. Below 35 degrees a forced defrost cycle is needed to avoid freeze ups. Visit this walk-in freezer page to learn more about defrost.

This is how a walk in 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 has risen to the set point of 40 degrees. The thermostat closes and the compressor and condenser fan comes on. The condenser fan may cycle on and off in cold ambient temperatures. The fans blow cold air out of the evaporator. The air circulates around the box absorbing heat. The warmed air is pulled into the back of the evaporator. The air is cooled as it passes through the evaporator.

The evaporator fan continues to run as the temperature drops to 35 degrees. There maybe slight ice 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.
 

The Thermostat is Satisfied

When the temperature reaches 35 degrees (40 degree set point minus 5 degree differential), the thermostat cuts the compressor and the condenser fan motor off. The evaporator fans continue to run. The fans in the walk in cooler should always be running.  Heat is absorbed through the walls, from door openings and from the product. The temperature continues to rise. Any frost that was built up on the evaporator will melt now. This is called off cycle defrost. The air needs to be at least 35 degrees for dependable defrost.

This is an important point. If the walk-in cooler can not reach 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. Liquid refrigerant can make it back to the compressor and cause compressor failure.

The air in the box continues to warm until it reaches 40 degrees. Then the thermostat calls for cooling again. A walk-in freezer works in the same way plus it has a forced defrost cycle.