You may remember refrigerators from your childhood, there would be frost built up around the coils that cool the freezer. If you let it build up long enough, the frost would get up to 6 inches thick and eventually there would be no room to put anything in the freezer!
This frost forms when water vapour hits the cold coils. The water vapor condenses into liquid water. Think of the water beading up on a glass of iced tea on a summer day — that is an example of water vapour in the air condensing. The same thing happens on the ice-cold freezer coils, except that when the water condenses onto the coils it immediately freezes. This is no good, but fridge makers have figured out a way to beat this. This feature is only available on double or multiple door fridge models, though.
A frost-free freezer has three basic parts:
- A timer
- A heating coil
- A temperature sensor
Every six hours or so, the timer turns on the heating coil. The heating coil is wrapped among the freezer coils. The heater melts the ice off the coils. When all of the ice is gone, the temperature sensor senses the temperature rising above zero degrees C and turns off the heater.
And voila, no more layers of ice in your freezer!