The thermal expansion is the tendency of metal in which the volume of metal changes with the variation in temperature. S. Timoshenko Scientific Paper 178, Westinghouse Research Laboratory. An example of this type of thermostat is thermostat used in electric iron. The sensing surface is the flat area of the “cup” or bimetal housing for thermostats with enclosed bimetal discs. The bimetallic thermometer uses the bimetallic strip which converts the temperature into the mechanical displacement. Fixed Temperature Thermostat Switches Bimetal Snap Disc Style Senasys manufactures a wide variety of bimetal, fixed temperature, snap disc thermostat switches. A thermocouple may be placed externally on a thermostat in place of a “dummy” (see figures 4 and 5). Brass and Steel; Aluminum vs Molybdenum. These thermostats use a sharp, semi-permanent, snap spring with a flat non-distorting bimetal. Most things get bigger when they heat up and smaller when they cool down (water is a notable exception: it expands when it heats up and when it freezes too).Mechanical thermostats use this idea (which is called thermal expansion) to switch an electric circuit on and and off.The two most common types use bimetallic … East Pittsburgh, Pa. Bimetal snap disc thermostats which provide an electrical resistance heater controlled by an external control circuit to change the operating temperature of the thermostat are known. These two metals have different expansion rates, triggered by thermal stimulation. Bimetallic strip thermostat mechanism. In above figure, the bimetal is a straight strip, however it can be made in the form of a coil (as shown in figure below) to increase the length in order to increase the sensitivity of thermostat… The working of the bimetallic strip depends on the thermal expansion property of the metal. Analysis of Bi-Metal Thermostats S. Timoshenko Author Information . Examples of metal combinations are. When the temperature reaches 50-70 degrees (F) the defrost bimetal turnd the defrost heater off. " The preferable location would be on the metal disc “cup” / mounting bracket at a point closest to the sensing surface. A bimetal thermostat is used to control the temperature of the heater coil in an electric iron. Author Affiliations. I looked for the bimetal defrost thermostat clipped on the evaporator. A bimetal thermostat uses a bimetallic strip (a strip consisting of two metals). This bimetal senses the temperature from the evaporator. Bimetal strips are used in thermostats. Perhaps the most common example of purely mechanical thermostat technology in use today is the internal combustion engine cooling system thermostat, used to maintain the engine near its optimum operating temperature by regulating the flow of coolant to an air-cooled radiator.This type of thermostat operates using a sealed chamber containing a wax pellet that … removed the the back panel to expose the evaporator. So how does a thermostat work? then I emptied the freezer. An example of such a thermostat is illustrated and described in U.S. Pat. Snap Disc Thermostats. Here, two strips of different metals are joined together to form a bimetallic strip. 2 Amp - 5 Amp, These thermostats were developed as a small, inexpensive, high performance bimetal thermostat which can be used as a controller. The strip bends in response to temperature changes to make or break an electrical contact. 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