Refrigerator Cooling Sensor NTC Thermistor and Temperature Sensor 510

Electric vs Hot Gas Defrost Thermostat Control

If using an active heating element with a defrost thermostat there are two options available, either an electrical element which is switched on, or hot gas which is released in to the evaporator using a valve.

Electrical defrost thermostat systems are cheaper to install and simpler to operate, due to the lack of mechanical parts involved in the system and because they are installed adjacent to the evaporator, but remain separate. However the downside of this is that because the electric heating element is installed in the refrigeration area itself it can result in more heat being transferred to the environment, rather than the evaporator. It will subsequently take longer to bring the refrigerator back down to the setpoint.

Conversely hot gas defrost systems work inside the evaporator by using a valve to allow high pressure, high temperature gas from the compressor to flow through the evaporator and warm the frost from inside. This heats the frost more precisely and melts it more efficiently than an electric heater, as well as resulting in less heat potentially being pushed in to the refrigeration area. The downsides to this are the increased cost and complexity of installation, the issue of wear and tear on mechanical parts that will require more regular maintenance, and, additionally, the increased potential for thermal shock damaging the evaporator as hot gas flows through it when it has been cooled to below 0°C.