THERMOSTAT - DEFROST
The defrost mechanism in a refrigerator heats the cooling element (evaporator coil) for a short period of time and melts the frost that has formed on it. The resulting water drains through a duct at the back of the unit. Defrosting is controlled by an electric or electronic timer: For every 6, 8, 10, 12 or 24 hours of compressor operation it turns on a defrost heater for 15 minutes to half an hour.
A defrost thermostat opens the heater circuit when the evaporator temperature rises above a preset temperature, 40°F (5°C) or more, thereby preventing excessive heating of the freezer compartment. The defrost timer is such that either the compressor or the defrost heater is on, but not both at the same time.
A thermostat is a component which senses the temperature of a physical system and performs actions so that the system's temperature is maintained near a desired setpoint by controlling the supply of gas or electricity to the heating or cooling system. Thermostats are used in any device or system that heats or cools to a setpoint temperature. A thermostat operates as a "closed loop" control device, as it seeks to reduce the error between the desired and measured temperatures. Sometimes a thermostat combines both the sensing and control action elements of a controlled system.
A thermostat exerts control by switching heating or cooling devices on or off, or by regulating the flow of a heat transfer fluid as needed to maintain the correct temperature. A thermostat can often be the main control unit for a heating or cooling system including central heating, air conditioners, as well as kitchen equipment including ovens and refrigerators.
Beverage-Air is a leading manufacturer of commercial refrigeration equipment to the foodservice industry. The company, based in Winston-Salem, N.C., provides top value, a diverse product offering, and unmatched quality in the commercial refrigeration equipment industry.
Click Image to Zoom In