HVAC- Heating, Ventilation, and Air Conditioning terms & definitions
Being an informed HVAC buyer begins with understanding the industry language.
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.
Basic Heating And Air Conditioning Definitions
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.
IAQ = Indoor Air Quality refers to the presence or absence of air pollutants in buildings. There are many sources of indoor air pollutants. The presence of sources of indoor air pollutants such as tobacco smoke and allergies, or by conditions that promote poor indoor air quality such as inadequate ventilation or moisture intrusion that can lead to mold growth, are used as indicators of potential health effects.
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.
Zone =A zone is the area that one thermostat is controlling. For example: A two story house with a thermostat on each floor has two zones, one for each floor.
Technical HVAC 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. How all heating and air conditioning equipment is sized. There are 12,000 btu's per ton of cooling.
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.)
Cubic Feet per Minute (CFM) = A standard measurement of airflow.
Defrost Mode = During the heating cycle of a heat pump, frost may build up on the outdoor coil. To remove the frost and maintain efficiency, the system will automatically defrost itself. This usually only takes a few minutes, then the system automatically switches back to heating. It is normal to see steam rising from the outdoor unit when this happens. )
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.)
Refrigerant Lines = aka Freon lines. Two copper lines that connect the outdoor air conditioner or heat pump to the indoor evaporator coil.
Ton = Heat pumps and air conditioners are generally sized in tons. Typical sizes for single family residences are between two and five tons. Each ton equals 12,000 Btuh. It is important to note that actual capacity is not constant and will change based on outdoor or indoor temperatures. The published capacity rating of air conditioners and heat pumps is based on performance at the ARI standard temperature levels of 95 F outside, 80 F inside.
Watt (W) = A Watt is a unit of electricity.
Kilowatt (kW) = A kilowatt equals 1,000 Watts. A kilowatt hour (kWh) is the amount of kilowatts of electricity used in one hour of operation of any equipment.