Below are some commonly used terms in the heating, ventilation and air conditioning industry. These may be useful when dealing with contractors or assessing a solution to your problem.

Air Conditioner - Assembly of equipment for the simultaneous control of air temperature, relative humidity, purity, and motion.

Air Cooled - Uses a fan to discharge heat from the condenser coil to the outdoors.

AFUE (Annual Fuel Utilization Efficiency) - A rating that denotes the efficiency of gas heating equipment. It is the amount of heating your equipment delivers for every dollar spent on fuel. A higher rating indicates more efficient equipment. This rating is calculated in accordance with the Department of Energy test procedures.

Air-Source - Air is being used as the heat source or heat sink for a heat pump.

Ambient Temperature - The temperature, usually of the air, that surrounds operating equipment.

BTU (British Thermal Unit) - The standard of measurement used for measuring the amount of heat required to raise the temperature of one pound of water by one degree (Fahrenheit).

BTUH - The number of BTUs in an hour. Central Air Conditioner System -System in which air is treated at a central location and carried to and from the rooms by one or more fans and a system of ducts.

Compressor - The pump that moves the refrigerant from the indoor evaporator to the outdoor condenser and back to the evaporator again. The compressor is often called "the heart of the system" because it circulates the refrigerant through the loop.

Condenser - A device that transfers unwanted heat out of a refrigeration system to a medium (either air, water, or a combination of air and water) that absorbs the heat and transfers it to a disposal point. There are three types of condensers: air-cooled condensers, water-cooled condensers, and evaporative condensers. The evaporative condenser uses a combination of air and water as its condensing medium. Most residential systems have an air-cooled condenser.

Condenser Coil - A series or network of tubes filled with refrigerant, normally located outside the home, that removes heat from the hot, gaseous refrigerant so that the refrigerant becomes liquid again.

Cooling Capacity - A measure of the ability of a unit to remove heat from an enclosed space.

COP - Coefficient of Performance of a heat pump means the ratio of the rate of useful heat output delivered by the complete heat pump unit (exclusive of supplementary heating) to the corresponding rate of energy input, in consistent units and under operating conditions.

DOE -The Department of Energy. A federal agency that sets industry efficiency standards and monitors the use of various energy sources.

EER - Energy Efficiency Ratio means the ratio of the cooling capacity of the air conditioner in British Thermal Units per hour, to the total electrical input in watts under ARI-specified test conditions.

Enthalpy - Heat content or total heat, including both sensible and latent heat. The amount of heat contained in a refrigerant at any given temperature with reference to -40°F.

Evaporator- Absorbs heat from the surrounding air or liquid and moves it outside the refrigerated area by means of a refrigerant. It is also known as a cooling coil, blower coil, chilling unit or indoor coil.

Evaporator Coil - A series or network of tubes filled with refrigerant located inside the home that take heat and moisture out of indoor air as liquid refrigerant evaporates.

Free Delivery - There are no ducts and the unit may be installed in the field without ducts if needed.

Ground-Source - The ground or soil below the frost line is being used as the heat source or heat sink for a heat pump.

Ground Water-Source - Water from an underground well is being used as the heat source or heat sink for a heat pump.

HVAC - Heating, ventilation, and air conditioning.

Heat Pump - An air conditioner capable of heating by refrigeration. It may or may not include a capability for cooling. Outside air or water is used as a heat source or heat sink, depending upon whether the system is heating or cooling.

Heating Capacity - A measure of the ability of a unit to add heat to an enclosed space.

HSPF -Heating Seasonal Performance Factor means the total heating output of a heat pump in British Thermal Units during its normal usage period for heating divided by the total electrical energy input in watt-hours during the same period.

Insulation - Any material that slows down the transfer of heat.

(K) Factor - The insulating value of any material. Also known as conductivity.

Kilowatt (kW) - Equal to 1,000 watts.

Kilowatt-hour (kWh) - A common unit of electrical consumption measured by the total energy created by one kilowatt in one hour.

Latent Heat - The heat energy needed to change the state of a substance (i.e.: from a liquid to a gas) but not it's temperature.

SEER-(Seasonal Energy Efficiency Ratio) - A rating that denotes the efficiency of air conditioning equipment. It is the amount of cooling your equipment delivers for every dollar spent on electricity. It is the ratio of cooling delivered by a system, measured in BTUs, to the dollar cost of the electricity to run the system, as measured in watt-hours. This ratio is determined using specified federal test procedures. The higher the SEER, the more efficient the unit. The more efficient the unit, the lower the operating cost.

Sensible Heat - Heat energy that causes a rise or fall in the temperature of a gas, liquid or solid when added or removed from that material. Sensible heat changes the temperature by changing the speed at which the molecules move.

Single Package -A central air conditioner which combines both condenser and air handling capabilities in a single packaged unit.

Split System - A central air conditioner consisting of two or more major components. The system usually consists of a compressor-containing unit and condenser, installed outside the building and a non-compressor -containing air handling unit installed within the building. This is the most common type of system installed in a home.

Supercooled Liquid - Liquid refrigerant cooled below its saturation point.

Subcooling - Creating a drop in temperature by removing sensible heat from a refrigerant liquid.

Superheated vapor - Refrigerant vapor heated beyond its saturation point. Superheating - Creating a rise in temperature by adding heat energy to a refrigeration vapor.

Ton -The unit of measurement for air conditioning system capacity. One ton of air conditioning removes 12,000 Btu's of heat energy per hour from a home. Central air conditioners are sized in tons. Residential units usually range from 1 to 5 tons.

Water-Source -Water is being used as the heat source or heat sink for a heat pump. Sources of underground water are wells and sources of surface water are lakes, large ponds, and rivers.

Watt - A unit of power that equals one joule per second. Named after James Watt.

Year-Round - Air Conditioner which uses gas or oil for heating.