Ice build-up on the evaporator coils - Walk-in coolers and freezers


Ice build-up on the evaporator coils (inside the walk-in, behind the fans) is sometimes caused by excessive warm air coming into the unit. The warm air turns into condensation which turns into ice buildup behind the coils and into the fans. The ice makes it difficult for the compressor to cool the unit, so it runs continuously and as a result keeps building up the ice and temperature keeps going up - a snowball effect. This happens mostly during summer when temperature and humidity are high. If unattended long term it may cause damage to the compressor and other components.


Warm air entering through the door can be caused by:

· Door not closing properly.

· Door gasket is damaged.

· Door sweep is damaged.

· Door closer is not functioning properly.

· Door left open while loading new product or cleaning the unit or other.

Note that there are many other causes related to ice build up in the system such as defective defrost timer, elements, defrost termination switch, thermostat, refrigerant leaks etc. We are not covering those here.


If you know ahead of time that you'll have the door open for an extended period of time to load new product, shut the compressor / condensing unit off. This can be done by adjusting the thermostat to higher than room temperature to prevent the compressor from turning on. Another way is to power down the compressor (condensing unit) at the electrical panel where possible or just unplug the unit for smaller units.

Do not turn off the evaporator coil (large component mounted on ceiling inside the walk-in with the fans). Leave that one powered on.

If the power breaker turns off both the condensing unit and the evaporator coil, that’s ok. The key is the compressor needs to be turned off to prevent ice build up. Leave it like that for the duration of product loading. Once done return the thermostat to the original setting or power unit back up.

Melting the ice:

1. Power down the compressor (or turn up thermostat to higher than room temperature). For walk-in units, try to remove power to the condensing unit (compressor) while leaving the evaporator (fans inside) powered on. That will accelerate the de-icing process. If that’s not possible, power the whole thing down or raise the thermostat to above room temperature (80F, 30C). Important thing is the compressor must be powered down during the ice melting phase otherwise the ice will continue to build up while you’re trying to melt it.

2. Move product to another unit if possible.

3. Leave unit off until all the ice is completely melted. It might require to be off overnight.

4. Check for ice behind the evaporator coils (behind the fans inside the cooler/freezer). Also check the condensate pan under the fans. All ice must be melted prior to turning the unit back on otherwise the ice building cycle will start up again. If you want to help the ice melting, you can put hot water in a hand spray bottle and squirt it on the ice. You must never use a water hose connected to city water or anything that will damage the coils. Remember the evaporator coils and fins are fragile and expensive to replace.

5. Once all ice is completely gone, power up the unit (or return the thermostat to original setting) and watch the temperature come down to proper temp. If it does not reach proper temp, call us and we'll send a technician to diagnose the problem.