Thermostats control many types of small and large home appliances. A thermostat is an electrical switch that opens and closes in response to temperature changes. Thermostats incorporate temperature sensors to measure temperature. These sensors command an electromechanical switch to turn a device on or off as needed to maintain a specific temperature level.
Thermostats are found in electrically heated tabletop appliances such as irons, fryers, broilers, toaster ovens, crock pots, coffee makers, hotplates and food warmers. They also are in glue guns, space heaters and personal care appliances like hair dryers, says the ATCOnline.com appliance parts website.
Most tabletop appliances use bimetallic thermostats that incorporate a metal strip that's a sandwich of metals that expand at different rates, says ATCOnline. The strip bends in response to temperature changes to make or break an electrical contact. Many models have a control knob that applies or releases tension on the strip to change the temperature point at which the strip will bend. This regulates the appliance's heat.
Bellows or pressure thermostats are built into large appliances such as refrigerators, freezers, air conditioners, gas and electric ovens and clothes dryers, says the Fuzing.com appliance parts website. This type has a long, thin, flexible tube filled with a liquid or gas that changes its volume at a known rate in response to temperature changes. The tube connects to a bellows that moves as the fill substance expands or contracts, opening or closing electrical contacts. A knob applies or releases tension on the bellows to control the temperature at which the thermostat acts.