AC Terminology


When you don't understand an air conditioning, heating or cooling term or phrase, check our HVAC Terminology glossary below for information. If you have any questions or we can be of any assistance, please feel free to contact Climate Care Air Conditioning & Heating at at 972-353-5257.


AC - Abbreviation for alternating current, a type of electric current in which the polarity is constantly reversing causing the electron flow to reverse.

ACCA - Air Conditioning Contractors of America.

AFUE - AFUE or (Annual Fuel Utilization Efficiency) is the measurement for heating efficiency. AFUE ranges from 80% to 95% for new systems. The higher the AFUE, the more efficiently the system performs, the greater your energy savings.

Air Conditioner - Any device that can change the temperature, humidity or general quality of the air.

Airflow - Airflow is the distribution or movement of air.

Air handler - An air moving and/or mixing unit. Residential air handlers include a blower, a coil, an expansion device, a heater rack and a filter. Heaters for air handlers are sold as accessories. In some models heaters are factory installed.

Btu - Btu is a British thermal unit of heat energy. One Btu is the amount of heat required to raise one pound of water by one degree Fahrenheit. The higher the Btu rating, the greater the heating capacity of the system. Btuh means British thermal units per hour.

CAE - CAE is the Combined Annual Efficiency to measure the amount of heat produced for every dollar of fuel consumed for both home and water heating.

Capacity - The output or producing ability of cooling or heating systems. Cooling and heating capacities are referred to in British thermal units (BTUs) per hour.

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

Central Air Conditioning System - A Central Air Conditioning System is the 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.

CFM - CFM 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.

Charge - Adding refrigerant to a system. This is refrigerant contained in a sealed system or in the sensing bulb to a thermostatic expansion valve.

Compressor - This is the heart of an air conditioning or heat pump system. It is part of the outdoor unit and pumps refrigerant to meet the cooling requirements of the system.

Condenser Coil (or outdoor coil) - In an air conditioner, the coil dissipates heat from the refrigerant, changing the refrigerant from vapor to liquid. In a heat pump system, the coil absorbs heat from the outdoors.

Condenser Fan - The fan that circulates air over the aircooled condenser.

Damper - The Damper is a movable plate, located in the ductwork that regulates airflow. Dampers are used to direct air to the areas that need it most. Typically used in a zoning application.

dB - A dB is a decibel of a unit that is used to measure the relative intensity of sound.

Defrost - To melt frost; as in from an air conditioner or heat pump coil.

Degree - A computation that gauges the amount of heating or cooling needed for a building. A degree day is equal to 65 degrees Fahrenheit minus the mean outdoor temperature.

Dehumidifier - An air cooler that removes moisture from the air.

Diffuser - A grille over an air supply duct having vanes to distribute the discharging air in a specific pattern or direction.

DOE - The DOE or Department of Energy is a federal agency responsible for setting industry efficiency standards and monitoring the consumption of energy sources.

Drain Pan - Also referred to as a condensate pan. This is a pan used to catch and collect condensate (in residential systems vapor is liquefied on the indoor coil, collected in the drain pan and removed through a drain line).

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

EER - Energy Efficiency Ratio (steady state).

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

ENERGY STAR® - ENERGY STAR is an EPA or 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 EPA is the Environmental Protection Agency develops and enforces federal environmental regulations. The EPA oversees the nationwide Energy Star® program.

Evaporator Coil - The evaporator coil is 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.

Expansion Valve - A refrigerantmetering valve with a pressure or temperature controlled orifice.

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

Fahrenheit - The temperature scale on which water freezes at 32 degrees and boils at 212 degrees; designated by the letter F. To convert Fahrenheit to Celsius, subtract 32 from the Fahrenheit number, multiply by 5 and divide by 9 (77 32 equals 45, times 5 equals 225, divided by 9 equals 25 degrees Celsius).

Fan - Any device that creates air currents.

Filter - Any device that removes impurities through a straining process.

Flue - Any vent or passageway that carries the products of combustion from a furnace.

Furnace - That part of the heating system in which the combustion of fossil fuel and transfer of heat occurs.

Fuse - A metal strip in an electrical circuit that melts and breaks the circuit when excessive current flows through it. The fuse is designed to break in order to save more expensive electrical components.

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

Heat Exchanger - An area, box or coil where heat flows from the warmer to the colder fluid or surface.

Heat Gain - Heat added to the conditioned space by infiltration, solar radiation, occupant respiration and lighting.

Heating Coil - Any coil that serves as a heat source.

Heat Loss - The rate of heat transfer from a heated space to the outdoors.

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 - Horizontal flow is when an air handler or furnace is positioned on its side and circulates air in one end and out the other. Horizontal flow is ideal for attic or crawl space installations.

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

Humidifier - A machine that adds water vapor to the air to increase humidity.

Humidistat - A humiditysensing control that cycles the humidifier on and off.

Humidity - The presence of water vapor in the air.

HVAC - HVAC is an acronym for Heating, Ventilation and Air Conditioning.

Ignition -The lighting of a fuel to make it burn.

Indoor Coil - Please refer to the evaporator coil for a complete description of the indoor coil.

ISO 9000- The ISO 9000 is a family of international standards for quality management and assurance.

Kilowatt (kW) - 1,000 watts.

MERV Rating - MERV Rating or Minimum Efficiency Reporting Value rating of a filter describes the size of the holes in the filter that allow air to pass through. The higher the MERV rating, the smaller the holes in the filter, the higher the efficiency.

Micron - A micron is a unit of measure equal to one millionth of a meter, or one thousandth of a millimeter.

Mini-split System - A mini-split system is a ductless air conditioning system that mounts in a single room, used to cool individual areas, particularly if a Window Unit is not desired or no windows are present.

OEM - Original equipment manufacturer.

Package Unit - A heating and cooling system contained in one outdoor unit. A package unit is typically installed beside, on the roof, or sometimes in the attic of a home.

Particles (Particulates) - Particulates are any substances measuring less than 100 microns in diameter. The EPA has found that small particles (less than 2.5 microns) are responsible for the health effects of greatest concern.

Programmable Thermostat - A programmable thermostat is a thermostat with the ability to record different temperature/time settings for your heating and/or cooling equipment.

R410A Refrigerant - R410A Refrigerant is a chlorine-free refrigerant that meets the EPA's newest, most stringent environmental guidelines.

Refrigerant - Refrigerant is a chemical that produces a cooling effect while expanding or vaporizing. Most residential air conditioning units contain the standard R-22 refrigerant, or Freon.

Refrigerant Lines - Refrigerant line are copper lines that connect the outdoor air conditioner or heat pump to the indoor evaporator coil.

Scroll Compressor - A scroll compressor is a specially designed compressor that works in a circular motion, as opposed to up-and-down piston action.

SEER - SEER is an efficiency rating that measures the cooling performance of air conditioners and heat pumps is rated using the SEER (Seasonal Energy Efficiency Ratio) system, which ranges from 13.00 to 20.00 for new systems. The higher the SEER, the better the efficiency, the greater the energy savings.

Single Package - A single package is a heating and cooling system contained in one outdoor unit.

Split System - The combination of an outdoor unit (air conditioner or heat pump) with an indoor unit (furnace or air handler). Split systems must be matched for optimum efficiency.

Thermostat - A thermostat is usually found on an inside wall, this device operates as a control to regulate your heating and cooling equipment, allowing you to adjust your home comfort at the touch of a switch.

Ton - A ton is a unit of measurement for determining cooling capacity. One ton equals 12,000 Btuh.

Two-Stage Operation - Two-Stage Operation provides two levels of heating or cooling output for greater temperature control, energy efficiency and improved indoor air quality.

Upflow - "Upflow" occurs when an air handler or furnace is installed in an upright position and circulates air through the side or bottom and out through the top. Typically used in a basement, closet and attic installations.

Variable Speed Motor - A variable speed motor is a motor that automatically adjusts the flow of warm or cool air for ultimate comfort.

Ventilator - A ventilator is a system that exchanges stale, recirculated indoor air with fresh, filtered outside air.

Volt - The unit of measure used to describe a difference in electrical potential. Abbreviated by the symbol "v".

Voltage - The force that pushes electrical current along wires and cables.

Watt - The unit of electrical power equal to the flow of one amp at a potential difference of one volt.

Window Unit - A window unit is an air conditioner designed to be placed in the window, used for cooling individual rooms.

Zoning - Zoning is a method of partitioning a home into independently controlled comfort zones for enhanced comfort and efficiency.


Additional Information:

Repair Or Replace | SEER | Spring & Summer Tips | Questions | HVAC Maintenance | Winter Furnace Tips

AC 101 | How an AC Works | AC Trouble-Shooting | AC Maintenance Tips | Improving Air Quality

Buying a New AC System | AC Terminology


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