All climate-control devices or systems have three basic components: a source of warmed or cooled air, a means of distributing the air to the rooms being heated or cooled, and a control, i.e. thermostat, used to regulate the system. The sources of warm air or cool air in a house often use the same distribution and control systems. If your house has central air conditioning, cool air usually flows through the same ducts as the heat and is regulated by the same thermostat. When a heating or cooling system malfunctions, any of these three basic components may be causing the problem.

A heat pump absorbs heat and moves it from inside your home to the outdoor air in the summer, then by use of a changeover valve it can reverse the process and absorb heat from the outdoor air and bring it inside for heating during the winter. When there is not enough heat-energy in the outdoor air to keep the desired temperature indoors a heat pump can be augmented by a set of electric heat strips.

A gas furnace burns fuel through a controlled combustion process to create heat and then transfer it into a home.

Both heating and air conditioning work on the principle that heat always moves from a warm object to a cooler one, just as water flows from a higher to a lower level. Furnaces and heaters put heat into the air to make your home warmer; air conditioners remove heat to make your home cooler.

All heating and cooling units burn some type of fuel such as gas, fuel oil or electricity. Air conditioners use electricity.