National HVAC/R Management Services - Toll Free 1-800-649-6804 HVAC/R Dictionary HVAC/R DICTIONARY Looking for our FAQ’s? Click here. A B C D E F G H I J K L M N O P Q R S T U V W X Y Z Words & Definitions for the letter A Absolute Humidity Amount of moisture in the air, indicated in grains per cu.ft³ Absolute Pressure Gauge pressure plus atmospheric pressure(14.7 lb. per sq. in².) Accessible Hermetic Assembly of motor and compressor inside a single housing unit Accumulator Storage tank that receives liquid refrigerant from evaporator and prevents it from flowing into suction line before it changes to a vapor ACR Tubing Tubing used in air conditioning and refrigeration. Ends are sealed to keep tubing clean and dry Air Conditioner Device used to control temperature, humidity, and cleanliness of air in a conditioned space Air Conditioning Control of the temperature, humidity, air movement, and cleaning of air, in a confined space Air-Cooled Condenser Heat of compression is transferred from condensing coils to surrounding air Air Diffuser Grille designed to direct airflow in desired patterns Air Handler Fan-blower, heat transfer coil(evaporator), heater and housing Algae Low form of plant life found floating in condensate drain pans and lines Alternating Current Electric current in which direction of flow reverses or alternates. In the US 60-cycle(hertz) current direction reverses every 1/120th of second Ambient Temperature Temperature of fluid or air that surrounds an object on all sides Ammeter >Electric meter, calibrated in amperes, used to measure current Amperage Electron or current flow of one coulomb per second past a given point in circuit Anemometer Instrument for measuring the rate of airflow or motion Anode Positive terminal of electrolytic cell Armature Part of an electric motor, generator or other devise moved by magnetism Aspect Ration Ratio of length to width of rectangular air grille or duct Aspirating Psychronometer Device that draws sample of air through it in order to measure humidity spiration Movement produced in a fluid by suction A.S.T.M. Standards Standards issued by the American Society of Testing Materials Atmospheric Pressure Pressure that gasses exert on earth; measure in pounds per square in.² Automatic Control Valve action reached through self-operated means, not requiring manual adjustment Automatic Defrost System of removing ice and frost from evaporators automatically Valve (AEV) Pressure-controlled valve that reduces high-pressure liquid refrigerant to low-pressure liquid refrigerant Words & Definitions for the letter B Back Pressure Pressure in low side of refrigerant system, also called suction pressure or low side pressure Back Seating Seal the joint where the valve stem goes through the valve body. This is accomplished by design of the valve Baffle Plate or vane used to direct or control movement of air or fluid in one direction only Ball Check Valve Valve assembly designed to permit flow of fluid in one direction only Barometer Instrument for measuring atmospheric pressure Bearing Low friction device for supporting and aligning a moving part Bleeding Slowly reducing the pressure of liquid or gas from a system by slowly opening a valve Boiling Point Boiling temperature of a liquid under a pressure of 14.7 psia Boiling Temperature Temperature at which a fluid changes from a liquid to a gas British Thermal Unit(Btu) Quantity of heat required to raise temperature of one lb. of water 1° F Words & Definitions for the letter C Capacitor Type of electrical storage device used in starting and/or running circuits on many electric motors Capacitor-Start-Motor Motor which has a capacitor in the starting circuit Capacity Refrigeration rating system. Usually measured in Btu per hour or watts Carbon Monoxide Colorless, odorless and poisonous gas(CO) produced when carbon or carbonaceous fuels are burned with too little air Cathode Negative terminal of an electrical device. Electrons leave at this terminal Cavitation Localized gaseous condition that is found within a liquid system Celsius Temperature Scale Temperature scale used in the metric system. Freezing point of water is 0°; boiling point is 100° Centimeter Metric unit of linear measurement which equals .3937 inch Change of State Condition in which a substance changes from a solid to a liquid or a liquid to a gas caused by the addition of heat. The reversal is when a substance changes from a gas to a liquid, or a liquid to a solid, caused by the removal of heat Check Valve Device which permits fluid to flow in one direction only Chill Factor Calculated number based on temperature and wind velocity Capillary Tube Pertaining to or occurring in or as if in a tube of fine bore Circuit A system that includes all component parts to complete its designated function; beginning and continuing through the various components, returning to its original starting point Circuit Breaker Safety device which automatically opens an electrical circuit it overloaded Comfort Zone Area on psychometric chart which shows conditions of temperature, humidity and sometimes air movement in which most people are comfortable Commutator Part of rotor in electric motor which conveys electric current to rotor windings Compression Term used to denote increase of pressure on a fluid by using mechanical energy Compressor Pump of a refrigeration mechanism which draws a low pressure on cooling side of refrigerant cycle and squeezes or compresses the gas into the high-pressure or condensing side of the cycle Compressor Displacement Volume, in cubic inches, represented by the area of compressor piston head(s), multiplied by the length of the stroke Compressor, Hermetic Compressor in which the driving motor is sealed in the same dome or housing as the compressor Compressor, Multiple Stage Compressor having two or more compressive steps. Discharge from each step is the intake pressure of the next in series Compressor, Reciprocating Compressor which uses a piston and cylinder mechanism to provide pumping action Condensate A fluid formed when a gas is cooled to its liquid state Condensate Pump Device to remove water condensate that collects beneath an evaporator Condensation Liquid or droplets which form when a gas or vapor is cooled below its dew point Condense Action of changing a gas to a vapor Condenser The part of a refrigeration mechanism which received hot, high-pressure refrigerant gas from the compressor and cools gaseous refrigerant until it returns to a liquid state Condenser Fan Electric motor and fan blade used to move air through air-cooled condenser Condensing Pressure Pressure inside a condenser at which refrigerant vapor gives up it’s latent heat of vaporization and becomes a liquid. This varies with pressure Condensing Unit Part of a refrigerating mechanism which pumps vaporized refrigerant from the evaporator, compresses it, liquefies it in the condenser and returns it to move to the evaporator Contaminant Substance such as dirt, moisture or other matter foreign to refrigerant or refrigerant oil in the system Control, Defrosting Device to Automatically defrost evaporator. It may operate by means of a time clock Control, Low-Pressure Cycling device connected to the low-pressure side of system Control, Motor Temperature of pressure-operated devices used to control the running of motors Control, Temperature Temperature-operated thermostatic device which automatically opens or closes a circuit Control Valve Valve which regulates the flow or pressure of a median which affects a controlled process Convection Transfer of heat by means of movement or flow of a fluid or gas Coulomb The quantity of electricity transferred by an electric current of one ampere in one second Current Transfer of electrical energy in a conductor by means of electrons changing positions Current Relay A device which opens or closes a circuit. It is made to act by a change of current flow in that circuit Cylinder Head Plate or cap which encloses compression end of compressor cylinder Cylinder, Refrigerant Steel cylinder used to store and dispense refrigerant. The color code painted on the cylinder indicates which refrigerant the cylinder contains Words & Definitions for the letter D Damper Device for controlling airflow Defrost Cycle Refrigerating cycle in which evaporator frost and ice accumulation is melted Defrost Timer Device connected into electrical circuit which shuts the unit off long enough to permit ice and frost accumulation on the evaporator to melt Degree-Day Unit that represents 1° degree of difference from inside temperature and the average outdoor temperature for one day Delta Transformer Three-phase electrical transformer which has ends of each of three windings electrically connected to form a triangle Demand Meter Instrument that measures the kilowatt-hour usage of a circuit or group of circuits Design Pressure Highest or most severe pressure expected during operation. Sometimes used as the calculated operating pressure plus an allowance for safety Detector, Leak Device used to detect and locate refrigerant leaks Dew Point Temperature at which vapor(at 100% humidity) begins to condense and deposit as a liquid Diaphragm Flexible material usually made of thin metal, rubber or plastic Dichlorodifluoromethane R-12, used in medium temperature applications Diode Two-element electron tube that allows more electron flow in one direction than the other Direct Current (DC) Electron flow which continually moves in one direction only Drier Substance or device used to remove moisture from a refrigeration system Drip Pan Pan-shaped panel or trough used to collect condensate from the evaporator Dry Bulb Temperature Air temperature as indicated by an ordinary thermometer Dry Cell Battery Electrical device used to provide DC electricity, having no liquid in the cells Dry Ice Refrigerating substance made of solid carbon dioxide which changes directly from a solid to a gas(sublimates). It’s subliming temperature is -109° F. (-78°C) Words & Definitions for the letter E Eccentric Circle or disk mounted off center on a shaft Effective Area The actual flow area of an air inlet or outlet. Gross area minus area of vanes or grille bars Electrolysis Movement of electricity through a substance which causes a chemical change in a substance or it’s container Electromagnet Coil of wire wound around a soft iron core. When electric current flows through the wire, the assembly becomes a magnet Electron Elementary particle or portion of an atom which carries a negative charge Electronic Leak Detector Electronic instrument which measure electronic flow across gas gap. Electronic flow changes indicate presence of refrigerant gas molecules Evacuation Removal of air(gas) and moisture from a refrigeration or air conditioning system Evaporation Term applied to the changing of a liquid to a gas. Heat is absorbed in this process Evaporator Part of a refrigeration mechanism in which the refrigerant vaporizes and absorbs heat Evaporator Fan Fan which increases airflow over the heat exchange surface of evaporators Words & Definitions for the letter F Fahrenheit Scale On a Fahrenheit thermometer, under standard atmospheric pressure, boiling point of water is 212° and freezing pint is 32° above 0° Female Thread The internal thread on fittings, valves and machine bodies refrigerant Freon Trade name for a family of synthetic chemical refrigerants manufactured by E.I. du Pont de Nemours & Co., Inc Fuse Electrical safety device consisting of strip of fusible metal in circuit that melts when circuit is overloaded Fusible Plug Plug or fitting made with a metal of a know low-melting temperature. Used as a safety device to release pressures in case of fire Words & Definitions for the letter G Galvanic Action The wasting away of two unlike metals due to electrical current passing between them. The action is increased in the presence of moisture Gas Valve Device in a pipeline for starting, stopping or regulating flow of gas Gasket Resilient(spongy) or flexible material used between mating surfaces of refrigeration unit parts, or on doors to give a leak proof seal Gasket, Foam Joint sealing material made of rubber or plastic foam strips Gauge, Compound Instrument for measuring pressures both above and below atmospheric pressures Gauge, Manifold Chamber device constructed to hold both compound and high pressure gauges. Valve control flow of fluids through it Gauge, Port Opening or connection provided for a service technician to install a gauge Grain A unit of weight and equal to 1/7000 lb. It is used to indicate the amount of moisture in the air Ground, Short Circuit Fault in an electrical circuit allowing electricity to flow into the metal parts of a mechanism Ground Wire Electrical wire which will safely conduct electricity from a structure into the ground Words & Definitions for the letter H Halide Torch Type of torch used to safely detect halogen refrigerant leaks in system Halogens Substance containing fluorine, chlorine, bromine and iodine Hanger Device attached to walls or ceilings for support of pipelines Head Pressure usually expressed in feet of water, inches of mercury Head, Static Pressure of fluid expressed in terms of height of column of the fluid, such as water of mercury Head Pressure Pressure which exists in condensing side of refrigeration system Head Pressure Control Pressure-operated control which opens electrical circuit if the high-side pressure becomes too high Header Length of pipe or vessel to which two or more pipe lines are joined carries fluid from a common source to various points of use Heat Form of energy which acts on substances to raise their temperature; energy associated with random motion of molecules Heat Exchanger Device used to transfer heat from a warm or hot surface to a cold or cooler surface.(Evaporators and condensers are heat exchangers) Heat Lag The time it takes for heat to travel through a substance heated on one side Heat Load Amount of heat, measured in Btu or watts, which is removed during a period of 24 hours Heat Pump Compression cycle system used to supply heat to a temperature-controlled space. The same system can also remove heat from the same space Heat Sink Relatively cold surface capable of absorbing heat Heat Transfer The movement of heat from one body or substance to another. Heat maybe transferred by radiation, conduction, convection or a combination of these three methods Heating Coil Heat transfer device consisting of a coil of piping, which releases heat Hertz(Hz) Correct terminology for cycles per second Hg.(Mercury) Heavy silver-white metallic element; only metal that is liquid at ordinary room temperature High Pressure Cut-Out Electrical control switch operated by the high-side pressure which automatically opens electrical circuit if too high pressure is reached High Side Parts of a refrigerating system which are under condensing or high-side pressure Horsepower A unit of power equal to 33,000 ft-lbs. of work per minute. One electrical horsepower equals 746 watts Hot Gas Bypass Piping system in refrigerating unit which moves hot refrigerant gas from condenser into low pressure side Hot Gas Defrost Defrosting system in which hot refrigerant gas from the high side is directed through evaporator for short period of time in order to remove frost from evaporator Humidity Moisture. Dampness in air Hydraulics Branch of physics having to do with the mechanical properties of water and other liquids in motion Hydrocarbons Organic compounds containing only hydrogen and carbon atoms in various combinations Hydrometer Floating instrument used to measure specific gravity of a liquid Hygrometer Instrument used to measure degree of moisture in the atmosphere Words & Definitions for the letter I Idler Pulley used on some belt drives to provide proper belt tension and to eliminate belt vibration Ignition Transfer Transformer designed to provide a high-voltage current. Used in many heating systems to ignite fuel, it provides a spark gap Impedance Opposition in an electrical circuit to the flow of an alternating current that is similar to the electrical resistance to a direct current Impeller Rotating part of the pump Induction Motor An AC motor which operates on the principle of a rotating magnetic field. The rotor has not electrical connection, but receives electrical energy by transformer action from field windings Inductive Reactance Electromagnetic induction in a circuit creates a counter or reverse(counter) emf(voltage) as the original current changes. It opposes the flow of alternating current Inhibitor Substance which prevents chemical reaction such as corrosion or oxidation Ion Group of atoms or an atom electrically charged Words & Definitions for the letter J Journal, Crankshaft Part of shaft which contacts the bearing on the large end of the piston rod Junction Box Box or container housing group of electrical terminals Words & Definitions for the letter K Kilometer Metric unit of linear measurement = 1000 meters Kilowatt Unit of electrical power, equal to 1000 watts Words & Definitions for the letter L Latent Heat Heat energy absorbed in process of changing form of substance(melting, vaporization, fusion) without change in temperature or pressure Latent Heat of Vaporization Amount of heat, required per pound of a substance to change its state from a liquid to a vapor(gas) Leak Detector Device or instrument such as a halide torch, an electronic snifter; or soap solution used to detect leaks Limit Control Control used to open or close electrical circuits as temperature or pressure limits are reached Liquid Receiver Cylinder (container) connected to condenser outlet for storage of liquid refrigerant in a system Liter Metric unit of volume which equals 61.03 cu. in³ Low Side That portion of a refrigeration system which is below evaporating pressure LP Fuel Liquefied petroleum used as a fuel gas Words & Definitions for the letter M Male Thread External thread on pipe, fittings and valves for making connections that screw together Manometer An instrument for measuring the pressure of gases and vapors. Gas pressure is balanced against column of liquid, such as mercury, in U-shaped tube Mass Quantity of matter held together so as to form one body MBH Thousands of British Thermal Units (82 MBH = 82,000 Btu) Megohm A unit of measure for electrical resistance. One megohm is equal to a million ohms Megohmmeter Instrument for measuring extremely high resistance’s (In the millions of ohms ranges) Metric System Decimal system of measuring Micro One millionth part of unit specified Micrometer Precision measuring instrument used for making accurate measurements to .001 to .0001 of an inch Micron Unit of length in metric system; a thousandth part (1/1000) of one millimeter Milli Combining form denoting one thousandth (1/1000); for example, millivolt means one thousandth of a volt Modulating Type of device or control which tends to adjust by increments (minute changes) rather than either “full on” or “full off” operation Molecule Smallest portion of an element or compound that retains chemical identity with the substance in mass Monochlorodifluoremethane Better know as Freon R-22. Cylinder color code is green (HVAC use) Motor Capacitor Single-phase induction motor with an auxiliary starting winding connected in series with a condensers (capacitor) for better starting characteristics Motor Control Device to start and/or stop a motor or hermetic motor compressor at certain temperature or pressure conditions Motor Starter High-capacity electric switches usually operated by electromagnets Words & Definitions for the letter N Neoprene Synthetic rubber which is resistant to hydrocarbon oil and gas Neutron That part of the atom core which has no electrical potential; electrically neutral Nominal Size Tubing Tubing measurement which has an inside diameter the same as iron pipe of the same stated size Nonferrous Group of metals and metal alloys which contain no iron Words & Definitions for the letter O Ohm A unit of measurement of electrical resistance. One ohm exists when one volt causes a flow of one ampere Ohmmeter An instrument for measuring resistance in ohms Ohm’s Law The mathematical relationship between voltage, current and resistance. Voltage = Amperes X Ohms Oil, Refrigeration Specially prepared oil used in refrigeration mechanisms which circulates with the refrigerant Oil Separator Device used to remove oil from gaseous refrigerant Open Circuit Interrupted electrical circuit which stops flow of electricity Operating Pressure The actual pressure at which the system works under normal conditions. This pressure may be positive or negative (vacuum) Organic Pertaining to or derived from living organisms Orifice Accurate size opening for controlling fluid flow Oscilloscope Fluorescent-coated tube which visually shows an electrical wave Overload Load greater than what the system or mechanism was intended Overload Protector Device, either temperature, pressure or current operated, which will stop operation of unit if dangerous conditions arise Ozone Bluish gaseous form of oxygen usually obtained by silent discharge of electricity in oxygen or air (03) Words & Definitions for the letter P Package Units Complete refrigerating system including compressor, condenser and evaporator located in the refrigerated space Packing Sealing device consisting of soft material of one or more mating soft elements. Reshaped by manually adjustable compression to obtain or maintain a leak-proof seal Piston Close-fitting part of plug which moves up and down in a cylinder Pitot Tube Tube used to measure air velocities Polyphase Motor Electrical motor designed to be used with a three or four-phase electrical circuit Potential Relay Electrical switch which opens on high voltage and closes on low voltage Potentiomenter Instrument for measuring or controlling by sensing small changes in electrical resistance Power Factor Correction coefficient for the changing current and voltage values a-c power PPM (Parts Per Million) Unit of concentration (for example, of solutions) Pressure The energy impact on a unit area; force or thrust on a surface. Pressure, Gauge Reading in pounds per in² above atmospheric Pressure, Head Force caused by the weight of a column or body of fluids. Expressed in feet, inches, or psi Pressure, Suction Pressure in the low-pressure side of a refrigeration system Pressure Drop The pressure difference at two ends of a circuit, or part of a circuit, the two sides of a filter Pressure Gauge An instrument for measuring the pressure exerted by the contents on its container Pressure Regulator, Evaporator Automatic pressure regulating valve mounted in suction line between the evaporator outlet and the compressor inlet. Maintain predetermined pressure and temperature in the evaporator Pressure Switch Switch operated by a rise or drop in pressure Protector, Circuit Electrical device which will open an electrical circuit if excessive electrical conditions occur Proton Particle of an atom with a positive charge PSI Symbol or initials used to indicate pressure measured in pounds per square in² absolute. Absolute pressure equals gauge pressure plus atmospheric pressure PSIG Symbols or initials used to indicate pressure in pounds per in² gauge. The “g” indicates that it is gauge pressure and not absolute pressure Psychrometer or Wet An instrument for measuring the relative humidity of atmospheric air. Bulb hygrometer Psychrometric Chart A chart that shows the relationship between the temperature pressure and moisture content of the air Psychrometric Measurement The measurement of temperature pressure and humidity, using a psychometric chart Pump Any one of the various machines which force a gas or liquid into — or draw it out of — something as by suction or pressure. Pump, Down The act of using a compressor or a pump to reduce the pressure in a container or a system. Pump, Reciprocating A pump having a reciprocating (moving up and down or back and forth) piston. Pump, Screw A pump having two interlocking screws rotating in housing. Purging Releasing compressed gas to the atmosphere through some part or parts for the purpose of removing contaminants from that part or parts. Normally Freon is the gas referred to. It is illegal to purge Freon to the atmosphere Pyrometer An instrument for measuring high temperatures. Words & Definitions for the letter Q There are currently no words with the letter Q in this dictionary. Words & Definitions for the letter R R-11 Trichloromonofluoromethane, a low pressure synthetic chemical refrigerant typically used in centrifugal chillers. (This refrigerant is no longer manufactured and was phased out as required by The Montreal Protocol) R-12 Dichlorodifluoromethan, a medium temperature, used in maketables and some coolers R-22 Monochlorodifluoromethane, low temperature, used in HVAC and occasionally coolers (The manufacture of new R22 will end in 2020 per The Montreal Protocol) R-502 Azerotropic mixture of R-12 and R-115. This is a low temperature freezer and ice machine application Radiant Heating Heating system in which warm or hot surfaces are used to radiate heat into the space to be conditioned Radiation The transfer of heat by heat rays Reciprocating Back and forth motion of a straight line Reed Value Thin, flat tempered steel plate fastened at one end Refrigerant Substance used in a refrigeration mechanism. It absorbs heat in the evaporator by a change of state from a liquid to a gas and releases it’s heat in a condenser as the substance returns from the gaseous state back to a liquid state Refrigerant Charge Quantity of refrigerant in a system Register Combination grille and damper assembly covering an air opening or the end of an air duct Relative Humidity Ratio of (difference between) amount of water vapor present in air to greatest amount possible at same temperature Relay An electromagnetic mechanism moved by a small electrical current in a control circuit. It operates a valve or switch in an operating circuit Relief Valve A safety device on a sealed system. It opens to release fluids before dangerous pressure is reached Remote System Refrigerating system in which the condensing unit is separated, in a different location from the evaporator or air handler Running Time Amount of time a condensing unit is run per hour or per 24 hours Running Winding Electrical winding of motor which has current flowing through it during normal operation of the motor Words & Definitions for the letter S Saddle Valve Valve body shaped so it may be silver brazed or clamped on to a refrigerant tubing surface Saturation Condition existing when substance contains all of another substance it can hold for that temperature and pressure Schrader Valve Spring loaded device which permits fluid flow in one direction when a center pin is depressed; in other direction when a pressure difference exists Seat That portion of a valve mechanism against which the valve presses to effect shutoff Second Law of Thermodynamics Heat will flow only from material at higher temperature to material at lower temperature Semi Conductor A class of solids whose ability to conduct electricity lies between that of a conductor and that of an insulator Semihermetic Compressor Hermetic compressor with service valves Sensible Heat Heat which causes a change in the temperature of a substance Separator, Oil Device to separate refrigerant oil from refrigerant gas and return the oil to compressor crankcase Service Valve Manually operated valve mounted on refrigerating systems used for service operation Short Cycling Refrigerating system that starts and stops more frequently than it should Shroud The housing over the condenser unit. Also called a doghouse. Protects unit from weather Sight Glass The glass window in a refrigeration line. The normal color of a center dot is green. A yellow center indicates moisture in the system. Bubbles in the sight glass, after the unit has been operating for a time may indicate a low refrigerant charge Silver Brazing A brazing process containing some silver. Must be used in refrigeration brazing Single Phase Motor Electric motor which operates on single phase alternating current Sling Psychrometer Measuring device with wet and dry bulb thermometers. Moved rapidly through air it measures humidity Slugging A condition in which a mass of liquid enters the compressor causing hammering. This breaks valves and washes lubricant out of bearings Solenoid Valve An electromagnet with a moving core. It serves as a valve or operates a valve Specific Gravity Weight of a liquid compared to water which is assigned value of 1.0 Splash System, Oiling Method of lubricating moving parts by agitating or splashing oil in the crankcase Split-Phase Motor A motor with two starter windings. Both windings are in use while starting. One is disconnected by a centrifugal switch after the motor attains speed. The motor then operates on one winding Split System A refrigeration or air conditioning installation that places the condensing unit outside or away from the evaporator. This also applies to heat pumps Squirrel Cage Fan which has blades parallel to a fan axis and moves air at right angles or perpendicular to the fan axis Standard Atmosphere Condition when air is at 14.7 psia pressure, at 68° F temperature and relative humidity of 36% Standard Conditions Used as a basis for air conditioning calculations; temperature of 68 F, pressure of 29.92 and relative humidity of 30% Starting Relay Electrical device which connects and/or disconnects the starting winding of an electric motor Starting Winding Winding in an electric motor used only briefly while the motor is starting Starter Motor Stationary part of an electric motor Subcooling Cooling of liquid refrigerant below it’s condensing temperature Sublimation Condition where a substance changes from a solid to a gas without becoming a liquid Suction Line Pipe used to carry refrigeration gas from the evaporator to the condenser Suction Pressure Control Valve Device located in the suction line which maintains constant pressure in the evaporator during the running portion of cycle Suction Service Valve A two-way manually operated valve located at the inlet to the compressor. It controls suction gas flow and is used to service the unit Suction Side Low-pressure side of the system extending from the refrigerant control through the evaporator to the inlet valve of the compressor Superheat 1: Temperature of vapor above its boiling temperature as a liquid at that pressure. 2: The difference between the temperature at the evaporator outlet and the lower temperature of the refrigerant evaporating in the evaporator Words & Definitions for the letter T Temperature-Humidity Index Actual temperature and humidity of air sample compared to air at standard conditions Test Light Light provided with test leads. Used to test or probe electrical circuits to determine if they have electricity Therm Quantity of heat equal to 100,000 Btu Thermal Relay Heat-operated electrical control used to open or close a refrigeration system electrical circuit. This system uses a resistance wire to convert electrical energy into heat energy Thermistor Basically a semiconductor which has electrical resistance that varies with temperature Thermocouple Device which generates electricity, using the principle that if two unlike metals are welded together and a junction is heated, a voltage will develop across the open ends Thermodynamics Part of science which deals with the relationship between heat and mechanical action Thermostat Device which senses ambient temperature conditions and in turn, acts to control a circuit Thermostatic Expansion Valve Control valve operated by temperature and pressure within the evaporator. It controls the flow of refrigerant. The control bulb is attached to outlet of evaporator Three-Phase Operating by means of combination of three alternating current circuits which differ in phase by 1/3 of a cycle Three-Way Valve Multi-orifice (opening) flow control valve with three fluid flow openings Ton of Refrigeration Refrigerating effect equal to the melting of 1 ton of ice in 24 hours. This may be expressed as follows: 288,000 Btu/24 hr., 12,000 Btu/1 hr, 200 Btu/min Torque Turning or twisting force Torque, Starting Amount of torque available, when at 0 speed to start and accelerate the load Total Heat Sum of both the sensible and latent heat Transducer Device turned on by charge of power from one source for purposes of supplying power in another form to second system Transformer Electromagnetic device which transfers electrical energy from primary circuit into variations of voltage in secondary circuit Transistor Electronic device commonly used for amplification, similar in use to an electron tube. Depends on conduction properties of semiconductors in which electrons moving in one direction are considered as leaving holes that serves as carriers of positive electricity in opposite direction Two-Way Valve Valve with one inlet port and one outlet port Words & Definitions for the letter U Ultraviolet Invisible radiation waves with frequencies shorter than wave lengths of visible light and longer than x-ray Universal Motor Electric motor which will operate on either a-c or d-c Words & Definitions for the letter V Vacuum Pressure lower than atmospheric pressure Vacuum Pump Special high efficiency device used for creating high vacuums for testing or drying purposes Valve Expansion A type of refrigerant control that maintains constant pressure in the low side of a refrigeration mechanism. Valve is caused to operate by pressure in the low or suction side. Often referred to as an automatic expansion valve or AEV Valve Service A device used to check pressures, service and charge refrigerating systems Valve Solenoid Valve made to work by magnetic action through an electrically energized coil Valve Suction Valve in refrigeration compressor which allows vaporized refrigerant to enter cylinder from suction line and prevent its return Valve Plate Part of compressor located between top of compressor body and the head. It contains compressor valves and ports Vapor Saturated Vapor condition that will result in condensation into droplets of liquid if vapor temperature is reduced Vapor Lock Condition where liquid is trapped in line because of bend or improper installation. Such vapor prevents liquid flow Vapor Pressure Pressure imposed by either a vapor or gas Vaporization Change of liquid into a gaseous state Variable Pitch Pulley A pulley which can be adjusted to provide different pulley drive ratios V-belt A type of belt commonly used in refrigeration work. It has a contact surface with the pulley that is in shape of letter V Vibration Eliminators Soft or flexible substance or device which will reduce the transmission of a vibration Voltage 1-Term used to indicate the electrical potential or electromotive force in an electrical circuit. 2-Voltage or electrical pressure which causes current to flow. 3-Electromotive force Voltmeter Instrument for measuring voltage in electrical circuit Volumetric Efficiency Term used to express the relationship between the actual performance of a compressor or of a vacuum pump and calculated performance of the pump based on its displacement Words & Definitions for the letter W Watt Unit of electrical power Wet Bulb Temperature The measure of the degree of moisture. It is the temperature of evaporation for an air sample Words & Definitions for the letter X There are currently no words with the letter X in this dictionary. Words & Definitions for the letter Y There are currently no words with the letter X in this dictionary. Words & Definitions for the letter Z There are currently no words with the letter X in this dictionary. Services About Us Technical Talk Join Our Team Contact Us Home 125 South Main Street, Freeport, NY 11520 Toll Free: 1-800-649-6804 Fax: 800-876-3928 | E-Mail: info@brinco.com ©2021 Brinco Mechanical Management Services, Inc. - All Rights Reserved.