Self-defrosting fridges, also known as frost-free or automatic defrost fridges, are designed to prevent the buildup of frost and ice inside the freezer compartment. They achieve this through a combination of temperature control, airflow, and the use of a component called a defrost heater.
Here's how it generally works:
Temperature Control: The fridge's thermostat continuously monitors the temperature inside the freezer and refrigerator compartments. When it detects that the temperature is getting too cold, it signals the cooling system to shut off, stopping the circulation of cold air.
Frost Accumulation: Despite the temperature control, some humidity from the air can still enter the freezer compartment, especially when you open the door. This humidity can cause condensation, and over time, it may form frost and ice on the walls of the freezer.
Defrost Cycle Activation: To prevent excessive frost buildup, the self-defrosting fridge employs a defrost cycle. This cycle is automatically activated based on the accumulated operating time of the compressor or the number of times the fridge's door has been opened and closed.
Defrost Heater Activation: When the defrost cycle is initiated, the defrost heater turns on. The defrost heater is typically located on the evaporator coils, which are responsible for cooling the freezer compartment. These coils are prone to frost accumulation.
Heating the Evaporator Coils: As the defrost heater warms up, it heats the evaporator coils, causing the frost and ice to melt. The water resulting from the melting frost then flows down into a drain pan located either at the back or bottom of the fridge.
Water Evaporation: The water collected in the drain pan will naturally evaporate due to the warmth generated by the fridge's compressor and condenser.
Resuming Cooling: After the defrost cycle is complete, the defrost heater turns off, and the compressor and cooling system resume their normal operation. The fridge continues to maintain the desired temperature without frost buildup until the next defrost cycle is required.
It's important to note that self-defrosting fridges are more common in modern refrigerators, while older models might not have this feature. Also, if you notice excessive frost buildup or issues with your fridge's cooling, it's a good idea to check the defrost system components like the defrost heater, thermostat, or defrost timer (if applicable) for any malfunctions.