United CoolAir Glossary
Absolute humidity
The weight of water vapor per unit; grams per cubic foot or grams per cubic meter.
Absolute pressure
Gauge pressure plus atmospheric pressure (14.7 psi).
Absolute temperature
Fahrenheit temperature plus 460º. Absolute zero is minus 460º F. Theoretically at or below this point there is no heat energy at all.
Absolute zero
Temperature at which all molecular motion ceases (-460°F and -273°C).
Absorbent
The ability to soak up another substance.
Absorber
A solution or surface that is capable of soaking up (taking in) another substance or energy form.
Absorption
The process of a material in extracting one or more substances as a gas or liquid accompanied by a physical change a chemical change or both.
Absorption chiller
A chiller that uses a brine solution and water to provide refrigeration without the aid of a compressor.
Absorption refrigerator
Refrigerator that creates low temperatures by using the cooling effect formed when a refrigerant is absorbed by chemical substance.
ACCA
Air Conditioning Contractors of America
Accumulator
A storage tank placed in a suction line for separating any liquid entrained in the suction gas.
Acid condition in system
Condition in which refrigerant or oil in system is mixed with acidic fluids.
ACR tubing
Tubing used in air conditioning and refrigeration. Ends are sealed to keep tubing clean and dry.
Activated alumina
A chemical that is a form of aluminum oxide. It is used as a drier or desiccant.
Activated carbon
Specially processed carbon used as a filter-drier; commonly used to clean air.
Actuator
That portion of a regulating valve that converts mechanical fluid, thermal energy or electrical energy into mechanical motion to open or close valve seats.
Add-on heat pump
A heat pump system used in conjunction with a fossil fuel furnace. Sometimes referred to as a dual fuel system.
Adiabatic compression
Compressing refrigerant gas without removing or adding heat.
Adsorbent
Substance with the property to hold molecule of fluids without causing a chemical or physical change.
Adsorption
The adhesion of a thin layer of molecules of a gas or liquid to a solid object.
Aeration
Act of combining a substance with air.
Agitator
Device used to cause motion in confined fluid.
Air
An invisible, odorless, and tasteless mixture of gases that surrounds the earth.
Air balancing
Process of adjusting the flow of air in duct systems.
Air change
The amount of air required to completely replace the air in a room or building; not to be considered air flow rate being delivered to the space.
Air cleaner
Device used for removal of air born impurities.
Air conditioner
Device used to control temperature, humidity, cleanliness, and movement of air in conditioned space.
Air conditioning
A process whereby the temperature, the moisture content or humidity, the quality, and the movement of air within a space are controlled. The term quality means both cleanliness and freshness of air.
Air diffuser
Air distribution outlet or grille designed to direct airflow into desired patterns.
Air gap
The space between magnetic poles or between rotating and stationary assemblies in a motor or generator.
Air handler
Fan-blower, heat transfer coil, filter, and housing parts of a system. (Typically meant as the evaporator section)
Air vent
Valve used to remove air from the highest point of a coil or piping assembly.
Air-cooled condenser
Heat of compression is transferred from condensing coils to surrounding air. This may be done either by convection or by a fan or blower.
Air-to-air heat pump
A heat pump that uses outdoor air as the source of heat and transfers it to air inside the space.
Alcohol brine
Water and alcohol solution that remains a liquid below 32°F (0°).
Altitude
The height at a point above a reference level, sea level or the earth's surface.
Ambient temperature
Temperature of a fluid (usually air) that surrounds an object.
Ammonia
Chemical combination of nitrogen and hydrogen (NH3). Ammonia refrigerant is identified as R-717.
Anemometer
Instrument for measuring the rate of airflow (using velocity).
Annealing
Cooling a metal slowly from a high temperature to make the metal soft.
Annual Fuel Utilization Efficiency (AFUE) rating
A rating system for furnaces that compares energy input and energy output.
Anticipator
A device used with a start-stop control to reduce the control differential.
ARI
Air-Conditioning and Refrigeration Institute.
ASA
Formerly, abbreviation for American Standards Association. Now known as American National Standards Institute (ANSI).
ASHRAE
American Society of Heating, Refrigeration and Air Conditioning.
Aspect ratio
Ratio of length to width of a rectangular air grille or duct.
Aspirating psychrometer
Device that draws a sample of air through it to measure the humidity.
Aspiration
Movement produced by suction.
ASTM Standards
Standards issued by the American Society for Testing and Materials.
Atmospheric dust spot efficiency
Measurement of a device's ability to remove atmospheric air from test air.
Atmospheric pressure
Pressure that gases in air exert upon the earth (14.695 psi or 29.92 in. Hg).
Atomize
To reduce to a fine spray.
Autotransformer
Transformer in which both primary and secondary coils have turns in common. Step-up or step-down of voltage is accomplished by taps on common winding.
Azeotropic mixture
A liquid mixture having constant maximum and minimum boiling points. Refrigerants comprising the azeotropic mixture do not combine chemically, yet the mixture provides constant characteristics.