Power must be turned off first to avoid injury. Deadly high voltage conditions could exist. Central heating and air conditioning systems use low voltage thermostats. Low voltage does not present a safety hazard, but damage can occur to the thermostat or other controls when disconnecting. Turn the power off.
Programmable thermostats offer new methods of conserving energy and increasing comfort.
Installation can be done by the homeowner, but there are different thermostats for each type of system. Heat pumps need a two stage thermostat. Fuel burning thermostats might need a thermostat with extra terminals if equipped with air conditioning. A programmable thermostat combines convenience with conservation. It may be programmed to conserve energy by lowering the demand for heat during inactive hours.