Confused about all that AC terminology? Here is a small glossary of terms that you may encounter during a consultation or service call!!!

Air Conditioner
An appliance, system, or mechanism designed to dehumidify and extract heat from an area. Usually this term is reserved for smaller self contained units such as a residential system.air handler A central unit consisting of a blower, heating and cooling elements, filter racks or chamber, dampers, humidifier, and other central equipment in direct contact with the airflow.

Air Handling Unit
Equipment with a heating element and/or cooling coil and other components in a cabinet or casing.

British thermal unit (BTU)
Any of several units of energy (heat) in the HVAC industry, each slightly more than 1 kJ. One BTU is the energy required to raise one pound of water one degree Fahrenheit, but the many different types of BTU are based on different interpretations of this “definition”.

Equipment that performs heat transfer to air when mounted inside an air handling unit or ductwork. It is heated or cooled by electrical means or by circulating liquid or steam within it.

A component in the basic refrigeration cycle that ejects or removes heat from the system. The condenser is the hot side of an air conditioner or heat pump. Condensers are heat exchangers, and can transfer heat to air or to an intermediate fluid (such as water or an aqueous solution of ethylene glycol) to carry heat to a distant sink, such as ground (earth sink), a body of water, or air (as with cooling towers).

A device that controls the operation of part or all of a system. It may simply turn a device on and off, or it may more subtly modulate the set point of components. Most controllers are automatic but have user input such as temperature set points, e.g. a thermostat. Controls may be analog or digital.

Carbon Monoxide
An odorless, colorless, tasteless, poisonous and flammable gas that is produced when carbon burns with insufficient air.

Central Air Conditioning System
System in which air is treated at a central location and distributed to and from rooms by one or more fans and a series of ducts.

Stands for Cubic Feet per Minute. This measurement indicates how many cubic feet of air pass by a stationary point in one minute. The higher the number, the more air is being moved through the ductwork by the system.

The part of the outdoor air conditioner or heat pump that compresses and pumps refrigerant to meet household cooling requirements.

The method by which air is channeled from the furnace or the blower coil throughout your home.

Electronic Air Cleaner
An electronic device that filters out large particles and bioaerosols in indoor air.

Energy Star®
An EPA (Environmental Protection Agency) designation attached to HVAC products that meet or exceed EPA guidelines for high-efficiency performance above the standard government minimums.
EPA. The Environmental Protection Agency develops and enforces federal environmental regulations. The EPA oversees the nationwide ENERGY STAR® program.

Evaporator Coil
The part of the air conditioner or heat pump that is located inside the air handler or attached to the furnace. Its primary function is to absorb the heat from the air in your house.

Heat Exchanger
Located in the furnace, the heat exchanger transfers heat to the surrounding air, which is then pumped throughout the home.

Heat Pump
A heat pump is an HVAC unit that heats or cools by moving heat. During the winter, a heat pump draws heat from outdoor air and circulates it through your home’s air ducts. In the summer, it reverses the process and removes heat from your house and releases it outdoors.

Horizontal Flow
When an air handler or furnace is positioned on its side and circulates air in one end and out the other. Ideal for attic or crawl space installations.

The Heating Seasonal Performance Factor is the heating efficiency rating for heat pumps. The higher the rating, the more efficient the heat pump.

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.

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

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

Refrigerant Charge (or, “charging the system”)
The procedure a technician performs to ensure that the system has enough of the right kind refrigerant for peak operating performance.

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, Return Air, Return Side
The path the air takes to get to an air-handling unit or furnace so it can be cooled or heated.  It is the “return” path.  The return side should be “balanced” with the supply side to ensure proper air flow and comfort.

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 number the more efficient the unit.

A measure of the size or cooling capacity of an air conditioner. One ton is equal to 12,000 BTU.