Auto-defrost

The defrost mechanism in a refrigerator heats the cooling element (evaporator coil) for a short period of time and melts the frost that has formed on it.

The defrost heater, having a typical power rating of 350W to 600W, is often mounted just below the evaporator in top and bottom-freezer models.

Air circulation helps sublimate any ice or frost that may form on frozen items in the freezer compartment.

While defrosting, this fan is stopped to prevent heated-up air from reaching the food compartment.

Some newer refrigerator/freezer models have a computer that monitors how many times each door is opened and uses this data to control defrost scheduling thereby reducing power use.

In laboratories, self-defrosting freezers must not be used to store certain delicate reagents such as enzymes, because the temperature cycling can degrade them.

In addition, water can evaporate out of containers that do not have a very tight seal, altering the concentration of the reagents.