What Are the Causes of Commercial Refrigerator or Freezer Defrost Problems?

Posted by Ancaster Food Equipment | 10-05-2021

Defrosting freezers are designed to make life easier. They avoid the build up of ice that can infringe on your freezer space and free up time from chipping away at the icy build up. In professional settings, refurbished commercial freezers also reduce risk of lost inventory.

Every time you need to defrost a freezer you need somewhere to store your goods which can put your food at risk of spoiling. However, even if you have a defrosting freezer system, you can encounter issues. Here we look at the issues that can lead to a faulty defrost system in your commercial refrigerators.

Refrigeration Cycles

Commercial fridges have a unique refrigeration cycle which can cause any moisture in the air to freeze and stick to the system’s evaporator and cooling coil. This is the main source of frost that defrosting systems target during the defrost cycle.

During the defrost cycle, the ice is melted so the coils remain clear of ice and can function properly. However, if the cycle is not performing properly, the frost has time to build up on the coils. This eventually blocks air flow, and your fridge can’t cool properly.

Understanding Defrost Cycle Termination

Defrost cycles are based on three possible triggers:

1. Temperature: In this case the defrost cycle is initiated by time and terminated by a temperature switch.

2. Pressure: For pressure, the defrost cycle is initiated by time and terminated by a pressure switch.

3. Time: In this case the defrost cycle is initiated by time and terminated by the defrost timer.

When using a pressure or temperature switch, if the termination switch fails, then it defaults to time which is usually set to the fail-safe of 35-45 minutes. However, the most popular method is temperature which triggers the defrost mechanisms and then returns to cooling to keep the frost under control.

For the pressure switch, a pressure control is connected to sense the pressure of the refrigerant in the evaporator.

The defrost timer is less popular because the times can vary so much based on things such as the ambient humidity level and how often someone opens the door. For example if the humidity level is low and the fridge isn’t used often, the frost will be less for the same amount of time compared to a higher humidity level with a more frequently used fridge.

Defrost Timer Issues

A common cause of defrost problems is the defrost timer that controls the cooling and defrosting cycle. As mentioned above, the fridge works in cycles.

In the case of your defrost system, it has a defrost heater that works with a defrost timer. The timer’s job is to switch the refrigerator between defrost and the cooling modes. When it isn’t working, you get a buildup of frost which interferes with air flow. However, the reverse can happen where the fridge stops at the defrost mode, melting all the frost and not kicking back into its cooling cycle.

Both scenarios interfere with your freezer’s function which can lead to melting and refreezing of your food, or inconsistent temperatures throughout the space.

Defrost Heater Malfunction

The defrost heater melts the frost on the evaporator coil. When this process doesn’t work, the frost accumulates on the coils which, as with the scenario above, causes issues with air flow. Without air flow, the cooling becomes less effective, resulting in cooling issues.

Broken or Faulty Thermostat

The thermostat senses the temperature of the cooling coils. When the coils are too cold, the thermostat triggers the defrost heater to kick in and start melting the frost. When it fails to function, it can either misread the temperature or simply not work so the defrost heater doesn’t know when to turn on.

Defrost Control Board Failure

The entire defrost cycle is controlled by the defrost control board which decides how often it needs to turn on the heater. When the board is failing, the defrost cycle will never be turned on so the frost continues to build up.

At Ancaster Food Equipment, during our refurbishing process we replace all components related to the defrost cycle with brand new OEM components.

From heating elements to temperature probes and controllers, you can be certain your defrost function remains fully operational, protecting your inventory and ensuring your food remains at the proper temperature.