Amount of moisture in the air, indicated in grains per ft3.
Gauge pressure plus atmospheric pressure (14.7 psi).
Temperature measured from absolute zero.
Absolute zero temperature
Temperature at which all molecular motion ceases (-460F and -273C).
The ability to soak up another substance.
A solution or surface that is capable of soaking up (taking in) anther substance or energy form.
The process of taking or soaking up into a substance.
A chiller that uses a brine solution and water to provide refrigeration without the aid of a compressor.
Refrigerator that creates low temperatures by using the cooling effect formed when a refrigerant is absorbed by chemical substance.
Assembly of motor and compressor inside a single bolted housing unit.
Storage tank that receives liquid refrigerant from the evaporator and prevents it from flowing into the suction line before vaporizing.
Acid condition in system
Condition in which refrigerant or oil in system is mixed with acidic fluids.
Tubing used in air conditioning and refrigeration. Ends are sealed to keep tubing clean and dry.
A chemical that is a form of aluminum oxide. It is used as a drier or desiccant.
Specially processed carbon used as a filter-drier; commonly used to clean air.
Active solar heating system
A system in which solar energy is absorbed in a collector, stored, and distributed by an auxiliary circulating system.
That portion of a regulating valve that converts mechanical fluid, thermal energy, or electrical energy into mechanical motion to open or close valve seats.
Compressing refrigerant gas without removing or adding heat.
Substance with the property to hold molecules of fluids without causing a chemical or physical change.
The adhesion of a thin layer of molecules of a gas or liquid to a solid object.
Act of combining a substance with air.
Device used to cause motion in confined fluid.
An invisible, odorless, and tasteless mixture of gases that surrounds the earth.
An inverted opening placed in the chimney of a gas furnace to prevent back pressure from outside wind from reaching the furnace flame or pilot.
Device used for removal of airborne impurities.
Coil on some types of heat pumps used either as an evaporator or a condenser.
Device used to control temperature, humidity, cleanliness, and movement of air in conditioned space.
Control of the temperature, humidity, air movement, and cleaning of air in a confined space.
Heat of compression is transferred from condensing coils to surrounding air. This may be done either by convection or by a fan or blower.
Mechanism designed to lower temperature of air passing through it.
Air core solenoid
A solenoid that has a hollow core instead of a solid core.
A system in which a blower is activated when a door is opened to blow across the open area, preventing the transfer of air between outdoors and indoors.
Evaporator defrosting that occurs as evaporator warms when the compressor is not running.
Air distribution outlet or grille designed to direct airflow into desired patterns.
The space between magnetic poles or between rotating and stationary assemblies in a motor or generator.
Fan-blower, heat transfer coil, filter, and housing parts of a system.
Sealed to prevent the passage of gas.
Air-to-air heat pump
A heat pump that uses outdoor air, as opposed to a geothermal heat pump.
Valve used to remove air from the highest point of a coil or piping assembly.
Device used to clean air while changing its humidity.
Water and alcohol solution that remains a liquid below 32F (0).
Low form of plant life, found floating free in water.
Screw with recessed, hex-shaped head.
Hexagonal (6-point) tip used to fit socket head screws or setscrews.
Alternating current (ac)
Electric current in which direction of flow alternates (reverses). In 60-cycle (Hertz) current, direction of flow reverses every 1/20th of a second.
The height at a point above a reference level, sea level, or the earth's surface.
An electronic device that provides a small amount of heat to the refrigeration compartment to ensure that the machinery continues to cycle when ambient temperatures are low.
Temperature of a fluid (usually air) that surrounds an object.
American Standard Pipe Thread
Type of screw thread commonly used on pipe and fittings to ensure a tight seal.
Electric meter used to measure current.
Chemical combination of nitrogen and hydrogen (NH3). Ammonia refrigerant is identified as R-117.
Electron or current flow past a given point in a circuit.
Unit of electric current equivalent to flow of one coulomb per second.
Term used to measure magnetic force. Represents product of amperes times number to turns in coil of electromagnet.
Electrical device that increases electron flow in a circuit.
Instrument for measuring the rate of airflow.
Type of globe valve design, having pipe openings at right angles to each other. Usually, one opening is in the horizontal plane and one is in the vertical plane.
Cooling a metal slowly form 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.
Positive terminal of electrolytic cell.
A device used with a start-stop control to reduce the control differential.
Band of sparks formed when an electrical discharge from a conductor jumps to another conductor.
Air-Conditioning and Refrigeration Institute.
Part of an electric motor, generator, or other device moved by magnetism.
Articulated connection rods
Short connecting rods in a compressor.
Formerly, abbreviation for American Standards Association. Now known as American National Standards Institute (ANSI).
Strong, fire-resistant, cancer-causing silicate.
Standard specifications issued by the American Society of Mechanical Engineers Boiler for the construction of boilers and pressure vessels.
Ratio of length to width of a rectangular air grille or duct.
Device that draws a sample of air through it to measure the humidity.
Movement produced by suction.
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.
Pressure that gases in air exert upon the earth (14.7 psi).
Smallest unit of an element that can exist alone or in combination.
Process of changing a liquid to minute particles or a fine spray.
Device with a helical shaft that, when rotated, can be used to move material.
Valve action reached through self-operated or self-actuated means, not requiring manual adjustment.
System of removing ice and frost from evaporators automatically.
Automatic expansion valve (AEV)
Pressure-controlled valve that reduces high-pressure liquid refrigerant and low-pressure refrigerant.
Automatic ice cube maker
Refrigerating mechanism designed to automatically produce ice cubes in quantities.
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.
Small evaporator consisting of coils of tinned tubing below the shelves in a display case.
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.