Glossary of Refrigeration Terms


A - B- C- D -E - F - G - H -I - J - K- L - M - N- O - P - Q - R - S - TU - V - W - X-Y-Z

Absolute Humidity - Amount of moisture in the air, indicated in grains per cubic foot.

Absolute Pressure - Gauge pressure plus atmospheric pressure (14.7 lbs. per sq. in.).

Absolute Temperature - Temperature measured from absolute zero.

Absolute Zero Temperature - Temperature at which molecular motion ceases.

Absorbent - Substance with ability to take-up, or absorb another substance.

Absorber - A solution or surface that is capable of soaking up (taking in) another substance or energy form.

Absorption Chiller - A chiller that uses a brine solution and water to provide refrigeration without the aid of a compressor.

Absorption Refrigerator - Refrigerator which creates low temperatures by using the cooling effect formed when a refrigerant is absorbed by chemical substance.

Accelerate - To add to speed; hasten progress of development.

Accumulator - Storage tank which receives liquid refrigerant from evaporator and prevents it from flowing into suction line.

Acid Condition - Condition in which refrigerant and/or refrigeration oil have become contaminated by the formation of acids. Typically caused by moisture introduced into system due to improper evacuation/dehydration of system after being open to, and exposed to the atmosphere.

ACR Tubing - Tubing used in refrigeration which has ends to keep tubing clean and dry.

Activated Alumina - Chemical 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.

Adiabatic Compression - Compressing refrigerant gas without removing or adding heat.

Adsorbent - Substance which has property to hold molecules 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.

Air - Invisible, odorless, and tasteless mixture of gases (consisting mostly of Nitrogen, Oxygen and Carbon Dioxide) which form earth's atmosphere.

Ampere - Unit of measure referring to the flow of electrons within a circuit. Both voltage (pressure) as well as amperage (flow) are required, or must be available to produce work (watts). In a circuit with a fixed resistance (Ohms), the value of volts vs. amps will change inversely in relation to each other.

ASME - American Society of Mechanical Engineers -Agency regulating design and construction of boiler and pressure vessels.

Back Pressure - Pressure in low side of refrigerating system; also called suction pressure or low side pressure.

Back Seating - Fluid opening/closing such as a gauge opening; to seat the joint where the valve stem goes through the valve body.

BTU - British Thermal Unit. In scientific terms, it represents the amount of energy required to raise one pound of water one degree Fahrenheit. One BTU is the approximate equivalent to the heat given off by a single wooden kitchen match.

Calcium Sulfate - Chemical compound (CaSO4) which is used as a drying agent or desiccant in liquid line (high side) filter-dryers.

Calibrate - to determine; position indicators as required to obtain accurate measurements.

Calorimeter - Device used to measure quantities of heat or determine specific heats.

Capacitance (C) - Property of nonconductor (condenser or capacitor) that permits storage of electrical energy in an electrostatic field.

Capacitor, Motor Running - Single or dual rated (two posts vs. three posts) devise which limits current and is permanently (hence phrase PSC - Permanent Split Capacitor) installed, in series, between the motors run and start windings. The current limiting characteristics prevent the start winding from burning. Also improves motor's efficiency (improves power factor) by realigning the motor's voltage and current sin waves. A PSC motor will generally consume 40-50% less electricity when compared to an equivalent Shaded Pole design motor.

Capacitor, Motor Starting - Device utilized in single phase compressors and/or electric motors to boost starting torque. Reduces inrush current (lights dimming) and associated internal heat generated with the motor windings. Typically black in color, and cylindrical.

CFM - A standard of airflow measurement. Cubic feet per minute.

Coil, Condenser unit, the coil dissipates heat from the refrigerant. Hot vapor refrigerant is compressed by the compressor, and the refrigerant condenses from a vapor to a liquid state. Subcooling of condensed liquid occurs when all vapor is condensed.

Coil, Evaporator where heat is absorbed by warm air passing across. Liquid refrigerant boils as it is metered into coil, and changes from liquid to vapor.

Cold - A sensation felt as a result of the absence of heat. (Similarity: There is no true definition of darkness, other than the absence of light.)

Compressor - The heart or "pump" within an air conditioning or heat pump system. The compressor maintains adequate pressure to cause refrigerant to condense and flow in sufficient quantities to meet the cooling requirements of the system.

Damper - Valve for controlling airflow. Found in duct work, movable plate opens and closes to control airflow. Can be manually or automatically controlled to regulate airflow to desired system zones.

Decibel (dB) - Unit used for measuring relative loudness of sounds. One decibel is equal to approximate difference of loudness ordinarily detectable by human ear, the range of which is about 130 decibels on scale beginning with one for faintest audible sound.

Ductwork - Round or rectangular pipes or controlled paths acting as conduit for return, mixed, makeup, supply or exhaust air. Supply air is downstream of high pressure side of fan. Return air is upstream of low pressure inlet of fan.

Ebulator - A pointed or sharp edged solid substance inserted in flooded type evaporators to improve evaporation (boiling) of refrigerant in coil.

Econimizer - A mechanism that removes flash gas from the evaporator.

Eddy Currents - Induced currents flowing in a core.

Fahrenheit Scale - On a Fahrenheit thermometer, under standard atmospheric pressure, boiling point of water is 212 deg. and freezing point is 32 deg. above zero on its scale.

Fan - A radial or axial flow device used for moving or producing artificial currents of air.

Farad - Unit of electrical capacity; capacity of a condenser which, when charged with one coulomb of electricity, gives difference of potential of one volt.

Field Pole - Part of stator of motor which concentrates magnetic field of field winding.

Filter - Device for removing small particles from a fluid.

Flame Test For Leaks - Tool which is principally a torch and when an air-refrigerant mixture is fed to flame, this flame will change color in presence of heated copper.

Gas - Vapor phase or state of a substance.

Gauge Manifold - A device constructed to hold compound and high pressure gauges containing hand valves to control flow.

Gauge, Vacuum - Instrument used to measure pressures below atmospheric pressure.

Halide Refrigerants - Family of refrigerants containing halogen chemicals.

Halide Torch - Type of torch used to detect halogen refrigerant leaks.

Head Pressure - Pressure which exists in condensing side of refrigerating system.

Head Pressure Control - Pressure operated control which opens electrical circuit if high side pressure becomes excessive.

Head, Static - Pressure of fluid expressed in terms of height of column of the fluid, such as water or mercury.

Head, Velocity - In flowing fluid, height of fluid equivalent to its velocity pressure.

Heat - Invisible energy (except high intensity infra-red) caused by the motion of molecules within any substance or matter. Will always travel from warm/hot to cold, via either or a combination of conduction, convection or radiation. Materials which resist flow or transfer of heat are called insulators, or insulation.

Heat Exchanger - A device for the transfer of heat energy from the source to the conveying medium, with the latter often being air or water. Most common combinations are: Refrigerant to air or Refrigerant to water (DX), Water to air (hydronic), Steam to air, Steam to water.

Humidity - The total amount of moisture in air. Relative humidity (RH), is the amount of moisture in air, relative to its total capability based upon its temperature (dewpoint). Moisture will condense on surfaces which are below this dewpoint.

Induction Motor - An AC motor which operates on principle of rotating magnetic field. Rotor has no electrical connection, but receives electrical energy by transformer action from field windings.

Insulation - Any material or substance which has the ability to retard the flow or transfer of heat.

Joule - Thomson Effect-Change in temperature of a gas on expansion through a porous plug from a high pressure to a lower pressure.

Junction Box - Group of electrical terminals housed in protective box or container.

Kilometer - Unit of electrical power, equal to 1000 watts.

Latent Heat - Heat energy absorbed in process of changing form of substance (melting, vaporization, fusion) without change in temperature or pressure. Also referred to as "hidden" heat.

Leak Detector - Device or instrument such as a halide torch, an electronic sniffer; or soap solution used to detect leaks.

Limit Control - Control used to open or close electrical circuits as temperature or pressure limits are reached.

Manifold, Service - A device equipped with gauges and manual valves, used by serviceman to service refrigerating systems.

Manometer - Instrument to measuring pressure of gases and vapors. Gas pressure is balanced against column of liquid such as mercury, in U-shaped tube.

Metering Device - TXV, capillary tube assembly, constant pressure expansion valve or bullet type piston orifice designed to regulate flow of liquid refrigerant entering the evaporator. Creates pressure drop to allow liquid refrigerant to boil and absorb latent heat. Separates high side of system from low side (as does the compressor).

Neutralizer - Substance used to counteract acids, in refrigeration system.

Off Cycle - That time period of a refrigeration cycle when the system is not operating.

OHM (R) - A standard unit of measure for electrical resistance. One ohm of resistance will allow one ampere of current to flow when one volt of electricity is applied to a circuit.

Ohmmeter - An instrument for measuring resistance in ohms.

Ohms Law - Mathematical relationships between voltage, current and resistance in an electric circuit, discovered by George Simon Ohm. It is stated as follows: voltage (E=Amperes (I) x Ohms (R); or E = I x R.

Pascal's Law - A pressure imposed upon a fluid is transmitted equally in all directions.

Pinch-Off Tool - Device used to press walls of a tubing together until fluid flow ceases.

Piston - Close fitting part which moves up and down in a cylinder.

Piston Displacement - Volume displaced by piston as it travels length of stroke.

PSC Motor - High-efficiency design motor used on virtually all of today's HVAC & R equipment requiring motors over 1/10hp. An upgrade from Shaded Pole design motors. See Capacitor, Motor Running.

Psychrometer - Either a sling type, or electronic. Instrument used to determine wet bulb temperatures and relative humidity. Combining RH with dry bulb temperature will yield total heat.

Range - Pressure or temperature settings of a control; change within limits.

Receiver Heating Element - Electrical resistance mounted in or around liquid receiver, used to maintain head pressures when ambient temperature is at freezing or below freezing.

Refrigerant - A substance produces a refrigerating or cooling (heat absorbing)effect while expanding or vaporizing.

Refrigeration - The moving of heat from an undesirable location, to that of a location where its presence is less undesirable.

Saddle Valve (Tap-A-Line) - Self piercing valve body designed to be permanently silver brazed or clamped to refrigerant tubing surface. Provides system access to monitor pressure, charge or evacuate refrigerant.

Safety Control - Device used to electrically shut down a refrigerating unit when unsafe pressures and/or temperatures exist.

Safety Motor Control - Electrical device used to open circuit if the temperature, pressure, and/or the current flow exceed safe conditions.

Safety Plug - Device which releases the contents of a container above normal pressures, and before rupture pressures are reached.

Saturation Temperature - The temperature where a refrigerant exists in both liquid and vapor form relative to its measured pressure.

Super Heat - The temperature rise within an evaporator/suction line assembly from the evaporator's saturation temperature.

Sub Cooling - Process whereas additional sensible heat (as opposed to latent heat) is removed from condensed refrigerant liquid prior to the metering device. The proper method for charging a system utilizing a TXV.

Temperature - Degree of hotness or coldness as measured by a thermometer; measurement of speed of motion of molecules.

Test Light - Light provided with test leads, used to test or probe electrical circuits to determine if they are alive.

Thermostat - A temperature control device. Typically mounted in conditioned space..

Therm - Quantity of heat equivalent to 100,000 Btu.

TON - A unit of measurement used for determining cooling capacity. One ton is the equivalent of 12,000 BTUs per hour.

TXV - Thermostatic Expansion Valve. A metering valve which acts as a superheat controller. Most are mechanically operated, and utilize a remote sensing bulb attached to the outlet of the evaporator assembly (via a sealed capillary tube) to regulate flow of sub-cooled liquid refrigerant at the evaporator inlet.

Vacuum - Reduction in pressure below atmospheric pressure.

Vacuum Control Systems - In some air conditioning systems, vacuum is used to operate dampers and controls in system.

Vacuum Pump - Special high efficiency device (pump) used create deep vacuum within an AC/R systems, for the purpose of moisture removal (dehydration), removal of non-condensibles and can also be used, as well, for leak checking.

Valve, Service - Typically, a multi-ported valve used by service technicians to isolate remote system components, as well as check pressures and charge refrigerating units.

Valve, Solenoid - Valve actuated by magnetic action by means of an electrically energized coil.

Volt - Electrical "pressure" applied to a circuit. One volt will cause one ampere of current (volume) to flow in a circuit containing one ohm of resistance.

Water -Cooled Condenser - Condensing unit which is cooled through use of water.

Watt - Unit of electrical power. Volts x Amps = Watts.

Wax - Undesirable component in many refrigeration lubricants, which may separate out of solution if cooled sufficiently.

Wet Bulb - Device used in measurement of relative humidity. Evaporation of moisture lowers temperature of wet bulb compared to dry bulb temperature in same area.

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