How does a thermostat work?
Materials • Honeywell Thermostat (Model number T87F 2873) • Hair dryer with both heating and cooling options, or other heating/cooling method Procedure • The thermostat must already be mounted vertically on a board or backing that is firmly placed. The students should not handle the thermostat, but they should carefully examine it. • Locate the bimetallic coil and the mercury bulb. Sketch a diagram of the thermostat in your data table, labeling any important parts. • Plug in the hair dryer. Blow hot air on the bimetallic coil. Observe what happens and record your observations. • Switch the hair dryer so that it blows cold (or room temperature) air. Observe any changes in the thermostat structure and record these. • Alternate the temperature of air on the thermostat. Observe the time it takes for the change in temperature to affect the position of the glass bulb.
A thermostat’s basic function is to regulate the operation of heating and cooling equipment in your home. You set the thermostat to the desired temperature and the thermostat turns the equipment on and off to maintain that temperature. A thermostat is essentially an automatic switch. The thermostat senses the temperature and turns the air conditioner or heater on and off as required to maintain the desired temperature. There are two basic types of thermostats: electromechanical and electronic. They both do the same thing but they do it in different ways. Additionally, of the two basic types, there are several varieties from which to choose. An electromechanical thermostat typically uses a bi-metal coil or strip which moves as it expands and contracts with temperature changes. Mounted on the bi-metal strip is a glass vial partially filled with mercury. As the vial is tilted on the back on the bi-metal strip, the mercury flows to the end of the vial where two electrical contacts are expo
A thermostat is a closed valve, held shut by spring tension. Once the coolant gets hot, a wax filled element in the upper part of the thermostat opens the valve. The heat melts the wax and expands it, that pushes the valve open. The thermostat is fully open at 20F above the rated temperature. As soon as the coolant temperature decreases, the wax cools off and contracts, allowing the valve to close. The thermostat ensures a constant operating temperature of the engine by open and shut the coolant circuit.
