How Does the Defrost on a Side by Side Refrigerator Work?

Defrost Timer

• The defrost timer is one of the components of a defrost system on a side-by-side refrigerator. This part of the defrost plays an important role by acting as a clock that tells the refrigerator when to stop cooling while simultaneously telling a heater to come on to melt away the frost buildup on the evaporator coil in the freezer. The timer runs all day and night and every six to eight hours it runs the defrost cycle to maintain frost-free conditions.

Heater

• The defrost heater is a small coil similar to those found on top of an electric range. The heating coils are located just below the evaporator coil. When they are activated by the timer they heat up and the radiant heat melts the frost away. After the timer indicates that enough time has passed to thoroughly clear the coil of frost, the heater turns off and the cooling system starts back up.

Thermostat

• The thermostat in the defrost system is important because it keeps track of the actual ambient temperature at the cooling coil. If the heat reaches a predetermined level then the switch in the thermostat turns off the heater to prevent unnecessary overheating. The timer may turn it off prior to the thermostat indication, but it is there to make sure the system continues to work properly.

Drainage

• Once the timer tells the heater to turn on and the heat from the heater melts away the frost, the job is still incomplete. The water that results from the melting has to go somewhere. There is a defrost drain located nearby the cooling coil that allows the water to trickle in and be carried by a tube to a catch pan below the refrigerator. This tube often runs through the back wall of the side-by-side refrigerator. The water drips into the pan on the outside of the unit where it evaporates naturally. If the drain or line becomes clogged, water will overflow into the bottom of the freezer side and form a sheet of ice in the lower bins.