Glossary Flashcards
Absolute Humidity
Amount of moisture in the air, indicated in the air, indicated in grains per cu. ft
Absolute Pressure
Gauge pressure plus atmospheric pressure (14.7 lb per square in.), equals absolute pressure
Absolute Temperature
Temperature measured from absolute zero.
Absolute Zero Temperature
Temperature at which all molecular motion ceases (-460 F and -275 C)
Absorbent
Substance with the ability to take up or absorb another substance
Absorption Refrigerator
Refrigerator which creates low temperatures by using the cooling effect formed when a refrigerant is absorbed by a chemical substance
Accumulator
Storage tank which receives liquid refrigerant from evaporator and prevents it from flowing into suction line before vaporizing
Acid Condition In System
Condition in which refrigerant or oil in system is mixed with fluids that are acidic in nature
Activated Alumina
Chemical form of aluminum oxide, used as a drier or dessicant
Activated Carbon
Specially processed carbon used as a filter-drier; commonly used to clean air
Actuator
That portion of a regulating valve which converts mechanical fluid, thermal energy or electrical energy into mechanical motion to open or close the valve seats
Adiabatic Compression
Compressing refrigerant gas without removing or adding heat
Adsorbent
Substance with the property to hold molecules of fluids without causing a chemical or physical change
Aeration
Process of combining substance with air
Agitator
Device used to cause motion in confined fluid
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 soils to surrounding air. This may be done by convection, fan, or blower.
Air Cooler
Mechanism designed to lower temperature of air passing through it
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
Air Infiltration
Leakage of air into rooms through cracks, windows, doors, and other openings
Air-sensing Termostat
Thermostat unit in which sensing element is located in a refrigerated space
Air, standard
Air having a temperature of 68 F (20 C), a relative humidity of 36 percent and under pressure of 14.70 psia. The gas industry usually considers 60 F (16 C) as the temperature of standard air
Air Vent
Valve either manual or automatic, for removing air from the highest point of a could or piping assembly
Air Washer
Device used to clean air while increasing or decreasing its humidity
Alcohol Brine
Water and alcohol solution which remains a liquid below 32 F (0C)
Algae
Low form of plant life, found floating free in water
Allen-Type Screw
Screw with recessed hex shaped head
Alternating Current (AC)
Electric current in which direction of flow alternates or reverses. In 60-cycle (hertz) current, direction of flow reverses every 1/129th of a second
Ambient Temperature
Temperature of fluid (usually air) which surrounds object on all sides
Ammeter
Electric meter, calibrated in amperes, used to measure current
Ammonia
Chemical combination of nitrogen and hydrogen (NH3). Ammonia refrigerant is identified as R-717
Ampere
Unit of electric current equivalent to flow of one coulomb per second
Anemometer
Instrument for measuring the rate of airflow or motion
Angle Valve
Type of globe valve design, having pipe openings at right angles next to each other. Usually, one opening is on the horizontal plane and one is on the vertical plane.
Anhydrous Calcium Sulphate
Dry chemical made of calcium, sulfur, and oxygen (CaSO4).
Annealing
Process of heat treating metal to get desired properties of softness and ductility. (Easy to form into new shape)
Anode
Positive terminal of electrolytic cell
Armature
Part of an electric motor, generator, or other device moved by magnetism
Atmospheric pressure
Pressure that gases in air exert upon the earth; measured in pounds per square inch (grams/per square centimeter)
Atomize
Process of changing a liquid to minute particles or a fine spray
Automatic Control
Valve action reached through self-operated or self-activated means, not requiring manual adjustment
Automatic Defrost
System of removing ice and frost from evaporators automatically
Automatic Expansion Valve (AEV)
Pressure-controlled valve which reduces high-pressure liquid refrigerant to low-pressure liquid refrigerant
Auto Transformer
Transformer in which both primary and secondary cools have turns in common. Step-up or step-down of voltage is accomplished by taps on common winding.
Azeotropic Mixture
Example of azeotropic mixture-refrigerant R-502 mixture consisting of 48.8 percent refrigerant R-22, and 51.2 percent R-115. The refrigerants do not combine chemically, yet azeotropic mixture provides refrigerant characteristics desired.
Back Pressure
Pressure in low side of refrigerating system; also called suction pressure or low-side pressure
Back Seating
Fluid opening/closing such as gauge opening or to seal the joint where the valve stem goes directly through the valve body
Baffle
Plate or vans used to direct or control movement of fluid or air within confined area
Ball Check Valve
Valve assembly (ball) which permits flow of fluid in one direction only
Barometer
Instrument for measuring atmospheric pressure. It may be calibrated in pounds per square inch, in inches of mercury in a column, or millimeters
Baudelot Cooler
Heat exchanger in which water flows by gravity over the outside of the tubes or plates
Bearing
Low friction device for supporting and aligning a moving part
Bellows
Corrugated cylindrical container which moves as pressures change, or provides a seal during movement of parts
Bellows Seal
Method of sealing the valve stem. The ends of the sealing material are fastened to the bonnet and to the stem. Seal expands and contracts with the stem level.
Bending Spring
Coil spring which is placed on the inside of outside of tubing to keep it from collapsing while bending it
Bernouli’s Theorem
In a stream of liquid, the sum of elevation head, pressure head, and velocity remains constant along any life of flow provided no work is done by or upon liquid in course of its flow, and decreases in proportion to energy lost in flow.
Bimetal Strip
Temperature regulating or indicating device which works on principle that two dissimilar metals with unequal expansion rates, welded together, will bend as temperatures change
Bleeding
Slowly reducing the pressure of liquid or gas from a system or cylinder by slightly opening a valve
Boiling Point
Boiling Temperature of a liquid under a pressure of 14.7 psia (760mm)
Boiling Temperature
Temperature at which a fluid changes from a liquid to a gas
Booster
Common term applied to the use of a compressor when used as the first stage in the cascade refrigerating system
Bore
Inside diameter of a cylinder
Bourdon Tube
Thin-walled tube of elastic metal flattened and bent into circular shape, which tends to straighten as pressure inside is increased. Used in pressure gauges.
Boyle’s Law
Law of physics - volume of a gas varies as pressure varies, if temperature remains the same. Example: If absolute pressure is doubled on quantity of gas, volume is reduced by one half. If volume becomes doubled, gas has its pressure reduced by half.
Brazing
Method of joining metals with non-ferrous filler (without iron) using heat between 800 F (427 C) and melting point of the base metals
Brine
Water saturated with a chemical such as salt
British Temperature Unit (BTU)
Quantity of heat required to raise the temperature of one pound of water by one degree Fahrenheit
Bulb. Sensitive
Part of sealed fluid device which reacts to temperature. Used to measure temperature or to control a mechanism.
Bunker
Space where ice or cooling element is placed in commercial installations
Bypass
Passage at one side of, or around, a regular passage
Calcium Sulfate
Chemical compound (CaSO4) which is used as a drying agent or desiccant in liquid line driers
Calibrate
To position indicators to determine accurate measurements
Capacitor-Start Motor
Motor which has a capacitor in the starting circuit
Capacity
Refrigeration rating system, Usually measured in Btu per hour or watts (metric)
Carbon Dioxide
Compound of carbon and oxygen (CO2) which is sometimes used as a refrigerant, Refrigerant number is R-744
Carbon Filter
Air filter using activated carbon as an air cleansing agent
Carrene
Refrigerant in Group One (R-1 I) Chemical combination of carbon, chloride, and flourine
Cascade Systems
Arrangement in which two or more refrigerating systems are used in series; useus evaporator of one machine to cool condenser of other machine. Produces ultra-low temperatures.
Cavitation
Localized gaseous condition that is found within a liquid stream
Celsius Temperature Scale
Temperature scale used in metric system. Freezing point of water is 0; boiling point of water is 100
Centigrade Temperature Scale
“Temperature scale used in metric system. Freezing point of water is 0; boiling point of water is 100”
Centimetre
Metric unit of linear measurement which equals .3937 inches
Central Station
Central location of condensing unit with either wet or air-cooled condenser.
Evaporator located as needed and connected to the central condensing unit
Centrifugal Compressor
Pump which compresses gaseous refrigerants by centrifugal force
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. Or the reverse, in which a substance changes from a gas to a liquid, or a liquid to a solid, caused by the removal of heat.
Charge
Amount of refrigerant placed in a refrigerating unit
Charles’ Law
Volume of a given mass of a gas at constant pressure varies according to its temperature
Check Valve
Device which permits fluid flow in one direction
Chill Factor
Calculated number based on temperature and wind velocity
Choke Tube
Throttling device used to maintain correct pressure difference between high side and low-side in refrigerating mechanisms.
Capillary tubes are sometimes called choke tubes
Circuit
Tubing, piping, or electrical wire installation which permits flow from the energy source back to energy sounce
Clearance Pocket Compressor
Small space in a cylinder from which compressed gas is not completely expelled. This space is called the compressor clearance space or pocket. For effective operation, compressors are designed to have as small a clearance space as possible.
Code Installation
Refrigeration or air-conditioning installation which conforms to the local code and/or the national code for safe and efficient installations.
Cold
The absence of heat; a temperature considerably below normal
Comfort Cooler
System used to reduce the temperature in the living space of homes. These systems are not complete air conditioners as they do not provide complete control of heating, humidifying, dehumidifying, and air circulation
Comfort Zone
Area on psychometric chart which shows conditions of temperature, humidity, and sometimes air movement in which people are most comfortable
Commutator
Part of rotor in electric motor which conveys electric current to rotor windings
Compound Gauge
Instrument for measuring pressures both above and below atmospheric pressure
Compound Refrigerating System
System which has several compressors or compressor cylinders in series.
The system is used to pump low-pressure vapors to condensing pressures.
Compression
Term used to denote increase of pressure on a fluid by using mechanical energy
Compression Gauge
Instrument used to measure positive pressure (pressure above atmospheric pressures) only. These gauges are usually calibrated from 0 to 300 lb. per square inch gauge, (psig) (0-21.1 kg/cm2)
Compression Ratio
Ratio of the volume of the clearance space to the total volume of the cylinder. In refrigeration it is also used as the ratio of the absolute low-side pressure to the absolute high-side pressure
Compressor
Pump of a refrigerating 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 the compressor piston head or heads 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 the series
Compressor, Open Type
Compressor in which the crankshaft extends through the crank-case and is driven by an outside motor. Commonly called external drive compressor
Compressor, Reciprocating
Compressor which uses a piston and cylinder mechanism to provide pumping action
Compressor, Single-Stage
Compressor having only one compressive step between low-side pressure and high-side pressure
Compressor Seal
Leak proof seal between crankshaft and compressor body in open type compressors
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 or vapor to a liquid
Condenser
The part of refrigeration mechanisms which receives hot, high-pressure refrigerant gas from the compressor and cools gaseous refrigerant until it returns to its liquid state
Condenser, Air-Cooled
Heat exchanger which transfers heat to surrounding air
Condenser Fan
Forced air device used to move air through air-cooled condenser
Condenser, Water-Cooled
Heat exchanger designed to transfer heat from hot gaseous refrigerant to water
Condensing Pressure
Pressure inside a condenser at which refrigerant vapor gives up its latent heat of vaporiazation and becomes a liquid. This varies with the temperature
Condensing Temperature
Temperature inside a condenser at which refrigerant vapor gives up its latent heat of liquid. This varies with the 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 the refrigerant control
Conductivity
Ability of a substance to conduct or transmit heat and/or electricity
Conductor
Substance or body capable of transmitting electricity or heat
Contrictor
Tube or orifice used to restrict the flow of a gas or liquid
Contaminant
Substance such as dirt, moisture, or other matter foreign to refrigerant or refrigerant oil in the system
Continuous Cycle Absorption System
System which has a continuous flow of energy input
Control
Automatic or manual device used to stop, start, and/or regulate flow of gas, liquid, and/or electricity
Control, Defrosting
Device to automatically defrost evaporator. It may operate by means of a clock, door cycling mechanism or during “off” portion of refrigerating cycle
Control, Low-Pressure
Cycling device connected to low-pressure side of system
Control, Motor
Temperature of pressure operated device used to control running of motor
Control, Pressure Motor
High or low pressure control connected into the electrical circuit and used to start and stop motor. It is activated by demand for refrigeration or for safety
Control, Refrigerant
Device Used to regulate flow of liquid refirgerant into evaporator. Can be a capillary tube, expansion valves, or high-side and low-side float valves
Control System
All of the compnents required for the automatic control of a process variable
Control, Temperature
Temperature-operated thermostatic device which automatically opens or closes a circuit
Control Valve
Valve which regulates the flow or pressure of a medium which affects a controlled process. Control valves are operated by remote signals from independent devices using any number of control media such as pneumatic, electric, or electro hydrualic
Convection
Transfer of heat by means of movement or flow of a fluid or gas
Convection, Forced
Transfer of heat resulting from forced movement of liquid or gas by means of a fan or pump
Convection, Natural
Circulation of a gas or liquid due to difference in density resulting from temperature differences
Conversion Factors
Force and power may be expressed in more than one way. A horse-power is equivalent to 33,000 ft. lb. of work per minute, 746 watts, or 2546 Btu per hour. These values can be used for changing horsepower into foot pounds, Brithish Thermal Units, or watts.
Cooler
Heat exchanger which removes heat from a substance
Cooling Tower
Device which cools by water evaporation in air. Water is cooled to wet bulb temperature of air
Copper Plating
Abnormal condition developing in some units in which copper is electrolytically deposited on some compressor sufaces
Corrosion
Deterioration of materials from chemical action
Counterflow
Flow in opposite direction
Couplings
Mechanical device joining refrigerant lines
“Cracking” A Valve
Opening a valve a small amount
Crank Throw
Distance between center line of main bearing journal and center line of the crankpin or eccentric
Crankshaft Seal
Leak proof join between crankshaft and compressor body
Critical Pressure
Compressed condition of refrigerant which gives liquid and gas the same properties
Critical Temperature
Temperature at which vapor and liquid have the same properties
Cross Charged
Sealed container of two fluids which together create a desired pressure-temperature curve
Cryogenics
Refrigeration which deals with producing -250 F and lower
Current
Transfer of electrical energy in a conductor by means of electrons changing position
Cut In
The temperature value or the pressure at which the control circuit closes
Cutout
Temperature value or pressure value at which the control circuit opens
Cylinder
1: Device which converts fluid power into linear mechanical force and motion. The usually consists of movable elements such as a piston and piston rod, plunger, or ram, operating withing a cylindrical bore
2: Closed container for fluids
Cylinder Head
Plate or cap which encloses compression end of compressor cylinder
Cylinder, Refrigerant
Cylinder in which refrigerant is stored and dispensed. Color code painted on cylinder indicates kind of refrigerant
Dalton’s Law
Vapor pressure created in a container by a mixture of gases is equal to the sum of individual vapor pressures of the gases contained in the mixture
Damper
Device for controlling airflow
Dearation
Act of separating air from substances
Defrost Cycle
Refrigerating cycle in which evaporator frost and ice accumulation are melted
Defrost Timer
Device connected into electrical circuit which shuts unit off long enough to permit ice and frost accumulation on evaporator to melt
Defrosting
Process of removing frost accumulation from evaporators
Degree-Day
Unit that represent one degree of difference from inside temperature and the average outdoor temperature for one day and is often used in estimating fuel requirements for a building
Dehumidifier
Device used to remove moisture from the air
Dehydrated Oil
Lubricant which has had most of its water content removed (dry oil)
Dehydrator-Receiver
Small tank which serves as liquid refrigerant reservoir and which also contains a desiccant to remove moisture. Used on most automobile air conditioning installations
De-Ice Control
Device for operating a refrigerating system in such a way as to provide melting of the accumulated ice and frost
Density
Closeness of texture or consistency of particles within a given substance. The weight per unit volume
Deodorizer
Device which absorbs or adsorbs various odors, usually by principle of absorption. Activated charcoal in commonly used
Desiccant
Substance used to collect and hold moisture in refrigerating systems. A drying agent. Common desiccants are activated alumina and silica gel
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 liquid
Diaphragm
Flexible material usually made of thin metal, rubber, or plastic
Dichlorodifluoromthane
Refrigerant commonly known as R-I2
Dielectric Fluid
Fluid with high electrical resistance
Differential
The temperature or pressure difference between cut-in and cut-out temperature or pressure of a control
Direct Current (DC)
Electron flow which moves continuously in one direction in circuit
Direct Expansion Evaporator
Evaporator using either an automatic expansion valve (AEV) or a thermostatic expansion valve (TEV) refrigerant control
Displacement, Piston
Volume obtained by multiplying area of cylinder bore by length of piston stroke
Distilling Apparatus
Fluid-reclaiming device used to reclaim used refrigerants. Reclaiming is usually done by vaporizing and then re-condensing refrigerant
Double Thickness Flare
Copper, aluminum, or steel tubing end which has been formen into two-wall thickness, 37 to 45 degree bell mouth or flare
Dowel Pin
Accurately dimensioned pin pressed into one assembly part to insure accurate alignment
Draft Gauge
Instrument used to measure air
Drier
Substance or device used to remove moisture from a refrigeration system
Dry Bulb Temperature
Air temperature as indicated by an ordinary thermometer
Dry Ice
Refrigerating substance made of solid carbon dioxide which changes directly from a solid to a gas (sublimates). Its subliming temperature is -109 F (-78 C)
Dry System
Refrigeration system which has the evaporator liquid refrigerant mainly in the atomized or droplet condition
Duct
Tube or channel through which air is conveyed or moved
Eccentric
Device which uses high fluid velocity, such as a venturi, to create low pressure or vacuum at its throat to draw in fluid from another source
Electric Defrosting
Use of electric resistance heating coils to melt ice and frost off evaporators during defrosting
Electric Water Valve
Solenoid type (electrically operated) valve used to turn water flow on and off
Electromagnet
Coil of wire wound around a soft iron core. When electric current flows through the wire, the assembly becomes a magnet
Electromotive Force (EMF) Voltage
Electrical force which causes current (free electrons) to flow or move in an electrical circuit. Unit of measurement is the volt.
Electronic Leak Detector
Electronic instrument which measures electronic flow across gas gap. Electronic flow changes indicate presence of refrigerant gas molecules
End Bell
End structure or plate of electric motor which usually hold motor bearings
Energy
Actual or potential ability to do work
Enthalpy
Total amount of heat in one pound of a substance calculated from accepted temperature base. Temperature of 32 F (0 C) is accepted base for water vapor calculation. For refrigerator calculations, accepted base is -40 F (-40 C)
Enthropy
1: Mathematical factor used in engineering calculations
2: Energy in a system
Ethane
Refrigerant sometimes added to other refrigerants to improve oil circulation. Known as (R-170)
Eutectic
The specific proportion of substances providing the lowest melting temperature between all possible proportions
Eutectic Point
Freezing point for eutectic solutions
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
Evaporative Condenser
Device which uses open spray or spill water to cool a condenser. Evaporation of some of the water cools the condenser water and reduces water consumption
Evaporator
Part of a refrigerating system in which the refrigerant vaporizes and absorbs heat
Evaporator, Dry Type
Evaporator in which the refrigerant is in the liquid droplet form
Evaporator, Flooded
Evaporator containing liquid refrigerant at all times
Evaporator Fan
Fan which increases air-flow over the heat exchange surface of evaporators
Exhaust Port
The opening which carries the fluid to the downstream pressure of a fluid system
Exhaust Valve
A movable port which provides an outlet for the cylinder gases in a compressor or engine
Expansion Join
Device in piping designed to allow movement of the pie causes by the pipe’s expansion and contraction
Expansion Valve
Device in refrigerating system which reduces the pressure from the high side to the low side and is operated by pressure
Expendable Refrigerant System
System which discards the refrigerant after is has evaporated
External Drive
Term used to indicate a compressor driven directly from the shaft or by a belt using an external motor. Compressor and motor are serviceable separately
External Equalizer
Tube connected to low pressure side of a thermostatic expansion valve diaphragm and to exit end of evaporator
Fahrenheit Scale
On a Fahrenheit thermometer, under standard atmospheric pressure, boiling point of water is 212 F and freezing point is 32 F
Fail-Safe Control
Device which opens a circuit when sensing element loses its pressure
Fan
Radial or axial flow device used for moving or producing flow of gases
Faraday Experiment
Silver chloride absorbs ammonia when cooled and releases it when heated. This is the basis on which some absorption refrigerators work
Female Thread
The internal thread on fittings, valves, machine bodies, and more
Field Pole
Part of stator of motor which concentrates magnetic field of field winding
Filter
Device for removing small foreign particles from a fluid
Flammable Liquids
Liquids having a flashpoint below 140 F (60 C) and a vapor pressure not exceeding 40 psi (absolute) (2.81 kg/cm2) at 100 F (38 c)
Flare
An enlargement at the end of a piece of flexible tubing by which the tubing is connected to a fitting or another piece of tubing. This enlargement is made at about a 45 degree angle. Fittings grip it firmly to make the joint leak-proof and strong
Flare Nut
Fitting used to clamp tubing flare against another fitting
Flash Gas
Instantaneous evaporation of some liquid refrigerant in evaporator which cools remaining liquid refrigerant to desired evaporation temperature
Flash Point
Temperature at which flammable liquid will give off sufficient vapor to support a flash flame but will not support continuous combustion
Float Valve
Type of valve which is operated by a sphere or pan which floats on liquid surface and controls level of liquid.
Flooded System
Type of refrigerating system in which liquid refrigerant fills most of the evaporator
Flooded System, High-Side Float
Refrigeration system which has a float operated by the level of the high-side liquid refrigerant
Flooded System, Low-Side Float
Refrigeration system which has a low-side float refrigerant control
Fluid
Substance in either a liquid or gaseous state. Substance containing particles which move and change position without separation of the mass
Flush
Operation to remove and material or fluids from refrigeration system parts by pumping them to the atmosphere using refrigerant or other fluids
Flux (Brazing, Smoldering)
Substance applied to surfaces to be joined by brazing or soldering to keep oxides from forming and to produce joints
Foaming
Formation of a foam in an oil-refrigerant mixture due to rapid evaporation of refrigerant dissolved in the oil. This is most likely to occur when the compressor starts and the pressure is suddenly reduced
Foot Pound
Unit of work. A foot pound is the amount of work done in lifting one pound one foot.
Force
Force is accumulated pressure and is expressed in pounds. If the pressure is 10 psi on a plate in 10 in. sq., the force is 100 lb. If pressure is 10kg/cm2 on a plate 10 cm2 in area, the force is 100kg
Force-Feed Oiling
Lubrication system which uses a pump to force oul to surfaces of moving parts
Freeze-Up
1: Formation of ice in the refrigerant control device which may stop the flow of refrigerant into the evaporator
2: Frost formation on an evaporator which may stop the airflow through the evaporator
Freezing
Change of state from liquid to solid
Freezing Point
Temperature at which a liquid will solidify upon removal of heat. The freezing temperature for water is 32 F. (0 C) at atmospheric pressure
Freon
Trade name for a family of synthetic chemical refrigerants manufactured be E. I. Dupont de Nemours & Co., Inc.
Frost Back
Condition in which liquid refrigerant flows from evaporator into suction line: usually indicated by sweating or frosting of the suction line
Frosting Type Evaporator
Refrigerating system which maintains the evaporator at frosting temperatures during all phases of cycle
Frozen
1: Water in its solid state
2: Seized (as in machine parts) due to lack of lubrication. The term “freeze-up” us often applied to this situation
Fusible Plug
Plug or fitting made with a metal of a known low temperature. Used as a safety device to release pressures in case of fire
Galvanic Action
Wasting away of two unlike metals due to electrical current passing between them. The action is increased in the presence of moisture
Gas
Vapor phase of a substance
Gas-Noncondensible
Gas which will not form into a liquid under the operating pressure temperature conditions
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 refrigerating unit parts or on refrigerator 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 above and below atmospheric pressure
Gauge, High Pressure
Instrument for measuring pressures in range of 0 psi to 500 psi (0 kg/cm2 to 35.2 kg/cm2)
Gauge, Low Pressure
Instrument for measuring pressures in range of 0 psi to 50 psi (kg/cm2 to 3.52 kg/cm2)
Gauge Manifold
Chamber device constructed to hold both compund and high-pressure gauges. Valves control flow of fluids through it
Gauge Port
Opening or connection provided for a service technician to install a gauge
Gauge Vacuum
Instrument used to measure pressures below atmospheric pressure
Grain
Unit of weight and equal to 1/7000 lb. It is used to indicate the amount of moisture in the air
Halide Torch
Type of torch use to safely detect halogen refrigerant leaks in system
Halogens
Substance containing fluorine, chlorine, bromine, and iodine
Head
Pressure, usually expressed in feet of water, inches of mercury, or millimeters of mercury
Head, Static
Pressure of fluid expressed in terms of height of column of the fluid, such as water or mercury
Head, Total Static
Static head from the surface of the supply source to the free discharge surface
Head Friction
Heads required to overcome friction of the interior surface of a conductor and between fluid particles in motion
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 too high
Head Velocity
Height of fluid equivalent to its velocity pressure in flowing fluid
