Air Conditioning Glossary


The distribution or movement of air.

Air-Conditioning and Refrigeration Institute (ARI)

ARI is an industry trade association that develops standards for measuring and certifying product performance. For instance, ARI Standard 270 provides guidelines for establishing sound levels for outdoor air-conditioning equipment.

Air Handler/Coil Blower

The indoor part of an air conditioner or heat pump that moves cooled or heated air throughout the ductwork of your building. An air handler is usually a furnace or a blower coil.

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.


Composite Fan Blades

Used in select Lennox outdoor air conditioner or heat pump units, blades are manufactured with rugged materials and an exclusive angled design that improve operation and durability, even in the harshest environments.


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

Condenser Coil

The outdoor portion of an air conditioner or heat pump that either releases or collects heat, depending on the time of the year.


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.

Dry-charged unit

An air-conditioner or heat pump that is shipped dry and charged with refrigerant at the place of installation. Dry-charged units are appropriate for homeowners who need a replacement unit compatible with R-22 refrigerant.

Dual Fuel

A comfort system that pairs an electric heat pump with a gas furnace, providing an energy-efficient alternative to the conventional furnace/air conditioner combination.


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

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 building.


An indoor air quality device that introduces moisture to heated air as it passes from the furnace into the ductwork for distribution throughout the building.


Heating, Ventilation and Air Conditioning.

Indoor Coil

See Evaporator Coil.

Outdoor Coil

See Condenser Coil.

Programmable Thermostat

A thermostat with the ability to record different temperature/time settings for your heating and/or cooling equipment.

R-22 Refrigerant

The old standard for residential air conditioners, the U.S. EPA is now phasing out R-22 refrigerant. Lennox offers dry-charged units for those who still have R-22 compatible systems.

R-410A Refrigerant

A chlorine-free refrigerant that meets the EPA’s newest, most stringent environmental guidelines.


A chemical that produces a cooling effect while expanding or vaporizing. Most commercial / industrial air conditioning units contain the standard R-22 refrigerant, or Freon.

Refrigerant Lines

Two copper lines that connect the outdoor air conditioner or heat pump to the indoor evaporator coil.

Scroll Compressor

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


The Seasonal Energy Efficiency Ratio is an energy efficiency rating for air conditioners. The higher the SEER, the better the energy performance, the more you save. The DOE’s established minimum SEER rating for cooling is 13.00.

Single Package

A heating and cooling system contained in one outdoor unit.

Split System

An HVAC system in which some components are located inside the structure of the building and some are located outside. Split systems should be matched for optimal efficiency.


Monitors temperature and humidity and adjusts heating or cooling system to maintain desired levels.


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.

Two-Stage Operation

Provides two levels of heating or cooling output for greater temperature control, energy efficiency and improved indoor air quality.


A system that exchanges stale, recirculated indoor air with fresh, filtered outside air.


A method of partitioning a building into independently controlled comfort zones for enhanced comfort and efficiency


Click for the Heating Glossary of Terms.

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