Many different thermostats are manufactured for use in heating and cooling systems. The design differences depend largely on the type of application.
The most common thermostat is the wall-mounted room thermostat used to control a heating and/or cooling system. The measuring element is contained in the thermostat unit itself. This distinguishes it from the remote-bulb-type thermostat used to measure temperatures in spaces separate from the location of the thermostat.
An insertion-type thermostat (or duct thermostat) is used to measure temperatures inside an air duct. The temperature-measuring element is contained in an insertion device that extends into the duct. The immersion-type thermostat is similar in design but is used to measure the temperature of fluids inside a pipe or tank. These thermostats are commonly used on water heaters.
A heating-cooling thermostat (also referred to as a summer-winter thermostat) is designed to be switched to either a heating or cooling application. The day-night thermostat (or electric clock thermostat) operates on a similar working principle except that it is designed to automatically switch from day to night operation and back again.
A multistage thermostat is designed to operate two or more circuits in sequence. These thermostats are used for line voltage or low-voltage temperature control of heating and cooling equipment. They are commonly used in heating and/or cooling systems where zone control is necessary.
A thermostat and humidistat can also be combined in the same control unit. These combined units sometimes also include the electronic air-cleaner control.
