Heating, Ventilating, and Air Conditioning
(HVAC) Definitions

Being an informed HVAC buyer begins with understanding the industry language. Several common terms used by manufacturers are as follows:

Efficiency Terms

In 1992, the Federal Government established minimum efficiency requirements for all heating and air conditioning equipment. If your present HVAC equipment -- a furnace, heat pump, or air conditioning system -- was purchased and installed before that date, it could be highly inefficient by today's standards.

Efficiency ratings are important to understand because installing a new unit could achieve significant energy cost reductions. And that could save you from the higher operating expenses of some pre-1992 equipment.

AFUE% = Furnace Efficiency. "AFUE" is a measure of a furnace's heating efficiency. It stands for Annual Fuel Utilization Efficiency. The higher the AFUE%, the more efficient the product. The government's established minimum rating for furnaces is 78%.

HSPF = Heat Pump Heating Efficiency. It stands for Heating Seasonal Performance Factor, or HSPF. The higher the HSPF rating, the more efficient a heat pump is at heating your home. There is no legislated minimum rating.

SEER = Cooling Efficiency. "SEER" is a measure of cooling efficiency for air conditioning products. SEER stands for Seasonal Energy Efficiency Ratio. The higher the SEER rating number, the more energy efficient the unit. The government's established minimum rating for air conditioning is 10.

Basic Heating And Air Conditioning Definitions

Air Handler. The portion of a central air conditioning or heat pump system that moves heated or cooled air throughout a home's ductwork. In some systems, a furnace handles this function.

Heat Source. A body of air or liquid from which heat is collected. In an air source heat pump, the air outside the house is used as the heat source during the heating cycle.

Indoor Coil. The portion of a heat pump or central air conditioning system that is located in the house and functions as the heat transfer point for warming or cooling indoor air.

Outdoor Coil/Condensing Unit. The portion of a heat pump or central air conditioning system that is located outside the home and functions as a heat transfer point for collecting heat from or dispelling heat to the outside air.

Single Package. A year 'round heating and air conditioning system that has all the components completely encased in one unit outside the home.

Split System. A heat pump or central air conditioning system with components located both inside and outside of a building -- the most common types installed in homes.

Supplementary Heat. The auxiliary or emergency heat provided at temperatures below a heat pump's balance point. It is usually electrical resistance heat.

Technical Heating And Air Conditioning Definitions

Balance Point. An outdoor temperature -- usually between 30°F to 45°F -- at which a heat pump's output exactly equals the heating needs of the house. Below the balance point, supplementary electric resistance heat is needed to maintain indoor comfort.

British Thermal Unit (Btu). The amount of heat required to raise the temperature of one pound of water (about one pint) by one degree Fahrenheit.

Coefficient of Performance (COP). A ratio calculated by dividing the total heating capacity provided by the heat pump, including circulating fan heat but excluding supplementary resistance heat (Btu's per hour), by the total electrical input (watts) x 3.412. (See Heating Seasonal Performance Factor, above.)

Energy Efficiency Ratio (EER). A ratio calculated by dividing the cooling capacity in Btu's per hour (Btuh) by the power input in watts at a given set of rating conditions, expressed in Btuh per watt (Btuh/watt). (See Seasonal Energy Efficiency Ratio, above.)

Some definitions supplied courtesy of ARI, the Air-Conditioning & Refrigeration Institute.