Three Types of Refrigerators
All refrigerators work on the same principle of cycling refrigerant through two sets of coils. The evaporator coils do the cooling, and the condenser coils release accumulated heat. Where fridges primarily differ is in how they defrost.
A manual defrost is the oldest and simplest type. As the name implies, you defrost these by turning them off and letting all the ice melt. The water then drips into a pan or runs into the fridge where you wipe it up.
Cycle defrost refrigerators have an evaporator plate in the refrigerator section that warms after each running cycle to eliminate frost buildup. But you have to defrost the freezer manually by turning a dial to the defrost mode. The water in most models flows into a channel in the back and then down through a tube to a drip tray under the fridge.
The frost-free refrigerator, the most common today, uses a heater to melt ice on the evaporator coils. The heater is turned on by a timer and automatically shuts off. An evaporator fan distributes the cold air through the freezer. Many models have an opening under the crisper drawers to draw water to the drip tray underneath.