Types of Thermostats

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.