Thermostats control nearly all types of heating and cooling equipment, keeping room temperatures within a set range. A thermostat has a means for sensing temperature and, based upon its reading, activating a switch.
Some do this mechanically, others electronically, cooupling sensors with circuitry to do the job. Most electronic types are like mini computers that can be programmed to automatically align heating and cooling to changing daily needs, eliminating unnecessary energy usage.
Not all thermostats work with all types of furnaces and heaters. For example, a forced-air thermostat won't necessarily work with a heat pump. Combination heating and air-conditioning systems require a control that will handle both modes. Typical programmable thermostats can handle both heat-only systems (forced-air, steam, hot-water and-in some cases-electric) and complete air conditioning systems.
The most sophisticated thermostats operate zone systems that split a house into two or more zones, each controlled by separate thermostatic settings. These thermostats open and close dampers in different runs of ductwork, sending warmed or cooled air to the areas where its wanted at various times of the day.
--Don Vandervort
