ACCA: The Air Conditioning Contractors of America, a national trade association that represents heating,ventilation, air conditioning, and refrigeration contractors.

A/C CONDENSOR:The outside unit of a heating or air conditioning system. Here the refrigerant condenses from a gas to a liquid and hot or cold air from the building is released to the outside.

BTU(British Thermal Unit): The measurement of heating and air conditioning capacity. A BTU is the amount of heat that must be added to one pound of water to raise its temperature one degree Fahrenheit.

DUCTING: Conduits used to carry air. In hvac systems, they carry air from the home through the forced air unit and back to the home.

FURNACE: A self-contained heating unit that is designed to deliver heated air to a home.

GAMA: Gas Appliance Manufacturing Association is a national trade association serving the interests of manufacturers of gas, oil, and electric appliances and equipment, components and related products used in residential, commercial, and industrial applications.

HEAT EXCHANGER: The part of a furnace that transfers heat from burning fuel to the air used to heat your home. A device, such as a condenser or evaporator, in which heat is added or removed in order to heat or cool your home.

HEAT PUMP: A single refrigeration system designed to provide both heating and cooling without the use of natural gas.

HSPF: Heating Seasonal Performance Factor, an equipment efficiency rating. As with MPG on a car, the higher the rating, the more fuel efficient the equipment is.

HUMIDIFIER: A device that adds moisture to warm air for your home.

HVAC: Heating, Ventilating, and Air Conditioning

INFILTRATION: Air that enters your home through holes, gaps, and cracks, (e.g., plumbing or electrical holes, the heating and air conditioning system, doors, and windows).

IAQ: Indoor air quality

LOAD CALCULATION: A mathematical determination of how much cooling and heating (BTUs) an HVACsystem must deliver for occupant safety and comfort. It is based on a variety of factors: square footage, building orientation, number of occupants, size and placement of rooms, number and size of windows and doors, amount of insulation, number of floors, and climate.

MANUAL J: An ACCA procedure covering the method for calculating heating and cooling requirements (load calculation) for single-family detached homes and mobile homes.

PM: Planned maintenance, which provides regular maintenance of your HVACR system. Most ACCA member contractors offer PM's, although they may use different names for them.

R-22 (Freon): A refrigerant containing chlorine used in air conditioning systems. The EPA has mandated that R-22 cannot be manufactured after 2010 because it has been linked to the depletion of the ozone layer and global warming. Most commonly referred to by its trademarked name, Freon.

R-410A: The refrigerant that replaces R-22. It does not contain chlorine and is not hazardous to the environment.

REFRIGERANT: A fluid that absorbs heat at low temperatures and rejects heat at higher temperatures.

RELATIVE HUMIDITY (RH): The percent of moisture actually in the air compared to the maximum amount of moisture the air can hold at that temperature.

RETURN AIR: The path the air takes to get to an air-handling unit or furnace so it can be cooled or heated

SEER: Seasonal Energy Efficiency Ratio, an equipment efficiency rating that measures how much energy it takes to cool the air. As with MPG on a car, the higher the seer number, the more efficient the unit.

SENSIBLE HEAT: The temperature of the air. This type of heat is measured with a thermometer.

SPLIT SYSTEM: A two-component heating and cooling system. The condensing unit is installed outside, the air handling unit is installed inside. Refrigerant lines and wiring connect them together.

SUPPLY AIR: The part of an HVAC system that takes (supplies) the conditioned air from the air-handling unit or furnace to your home.

ZONED SYSTEM: A single HVAC system that can meet different heating and cooling needs in different areas (zones). Each zone of a home has its own thermostat with which it can regulate the temperature and humidity in its area.