Glossary: C

The housing of a refrigerator.

Cabinet volume
The volume of the interior cabinet dimensions.

Calcium sulfate
Chemical compound (CaSO4) that is used as a drying agent or desiccant in liquid line driers.

Position indicators to determine accurate measurements.

A service call to repair a problem that had been improperly repaired.

Two different calorie units are used by scientists. The calorie used by medical science is a small heat unit. It equals the heat required to raise the temperature of one gram of water one degree Celsius (C). The calorie used by engineering science is a lager heat unit (see Kilocalories).

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

Oblong mechanical component that produces a reciprocating motion when rotated.

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

Capacitive reactance
The opposition, or resistance, to an alternating current as a result of capacitance; expressed in ohms.

Electrical storage device used to start and run circuits on many electric motors.

Capacitor-start motor
A motor with a capacitor in the starting circuit.

Refrigeration rating system. Usually measured in Btu per hour or watts.

Capillary tube system
A refrigerant control system in which pressure difference is maintained through the use of a thin capillary tube.

Carbon dioxide (CO2)
Compound of carbon and oxygen that is sometimes used as a refrigerant. Refrigerant number is R-744.

Carbon dioxide indicator
Instrument used to indicate the percentage of carbon dioxide in stack gases.

Carbon filter
Air filter using activated carbon as an air cleansing agent.

Carbon monoxide (CO)
Colorless, odorless, and poisonous gas produced when carbon fuels are burned with too little air.

Carbon tetrachloride (CCI4)
Colorless, nonflammable, and toxic liquid used as a solvent.

Refrigerant in Group A1 (R-11). Chemical combination of carbon, chlorine, and fluorine.

Cascade systems
Arrangement in which two or more refrigerating systems are used in series; uses evaporator of one machine to cool condenser of other machine. Produces ultra-low temperatures.

Negative terminal of an electrical device. Electrons leave at this terminal.

Localized gaseous condition within a liquid stream.

Celsius temperature scale
Temperature scale used in metric system. Freezing point of is 0C, boiling point is 100C.

Centigrade temperature scale
See Celsius temperature scale.

Metric unit of linear measurement, equal to 0.3937.

Central air conditioning
A system capable of providing heating, cooling, humidifying, and dehumidifying.

Centralized computer control
Energy control device centrally located, that makes control decisions based on operating data, programmed information, and stored data. Can be used to optimize energy consumption of many devices throughout a building.

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 that compresses gaseous refrigerants by centrifugal force.

Centrifugal force
Force that pushes a rotating object away from the center of its rotation.

Centrifugal switch
An electrical switch that is opened and closed by centrifugal force.

Ceramic ignitor
Electric ignition system used in a water glycol solution, forced-air furnace. Electrically heated to create ignition of the gas-air mixture in combustion chamber.

Change of state
Condition in which a substance changes from one state (solid, liquid, or gas) to another.

Amount of refrigerant placed in a refrigerating unit.

Charging board
Specially designed panel or cabinet fitted with gauges, valves, and refrigerant cylinders used for charging refrigerant and oil into refrigerating mechanisms.

Charles' Law
A law stating, that at a constant pressure, mass and temperature of a gas are inversely proportional.

Check valve
Device which permits fluid flow in only one direction.

Chemical refrigeration
System of cooling using a disposable refrigerant. Also called expendable refrigerant system.

Air conditioning system that circulates chilled water to various cooling coils in an installation.

Chill factor
Calculated number, based on temperature and wind velocity, that indicates chill effect.

Vertical shaft enclosing one or more flues for carrying flue gases to the outside atmosphere.

Chimney connector
Conduit (pipe) connecting the furnace to the vertical flue.

Chimney effect
Tendency of gas to rise when heated.

Chimney flue
Flue gas passageway in a chimney.

Chlorofluorocarbons (CFCs)
Refrigerants that are composed of chlorine, fluorine, and a hydrocarbon (methane). CFCs deplete the ozone layer.

Choke tube
Throttling device used to maintain correct pressure difference between high-side and low-side in refrigerating mechanism. Capillary tubes are sometimes called choke tubes.

Tubing, piping, or electrical wire installation that permits flow to and from an energy source.

Circuit breaker
Safety device that automatically opens an electrical circuit if overloaded.

Circuit, parallel
Arrangement of electrical devices in which the current divides and travels through two or more paths and then returns through a common path.

Circuit, pilot
Secondary circuit used to control a main circuit or a device in the main circuit.

Circuit, series
Electrical path (circuit) in which electricity to operate a second device must pass through first; Current flow travels, in turn, through all devices connected together.

Clean room
A room in which special efforts are made to eliminate dust and other contaminants.

Clearance space
Small space in a cylinder from which compressed gas is not completely expelled. For effective operation, compressors are designed to have as small a clearance space as possible.

The average weather conditions for a region.

Climate control
Devices used to maintain an ideal climate in a space.

Closed circuit
Electrical circuit in which electrons are flowing.

Clutch, magnetic
Clutch built into automobile compressor flywheel, operated magnetically, which allows a pulley to revolve without driving the compressor when refrigeration is not required.

Code installation
Refrigeration or air conditioning installation that conforms to the applicable codes.

Coefficient of conductivity
Measure of the relative rate at which different materials conduct heat. A good conductor of heat has a high coefficient of conductivity.

Coefficient of expansion
A measure of the change in size of a material as the temperature changes.

Coefficient of performance (COP)
Ratio of the work performed to the energy used.

Using waste energy as a primary heat source. Example: The use of waste heat from an electrical energy generation system to heat a building.

The absence of heat; a temperature considerably below normal.

Cold ban
A plastic trim piece used to reduce heat flow between the outer and inner shell of a refrigerator door.

Cold junction
That part of a thermoelectric system which absorbs heat as the system operates.

Cold wall
Refrigerator construction that has the inner lining of the refrigerator serving as the cooling surface.

Semiconductor section of a transistor, connected to the same polarity as the base.

Miniature cells peculiar to meats, fish, and poultry which, if disrupted, cause food to become rancid. Low temperatures minimize this action.

Combined Annual Efficiency (CAE) ratio
Rating system used for combined heating systems, which heat both air and water.

Combustible liquids
Liquid having a flash point above 140F (60C); known as Class 3 liquids.

The process of igniting and burning.

Comfort chart
Chart used in air conditioning to show the dry bulb temperature, humidity, and air movement for human comfort.

Comfort cooler
System used to reduce the Temperature in the living space in homes. These systems are not complete air conditioners as they do not provide complete control of heating, humidifying, dehumidification, and air circulation.

Comfort zone
Area on psychrometric chart that shows conditions of temperature, humidity, and sometimes air movement in which most people are comfortable.

Commercial system
A refrigeration or air conditioning unit that is used in commercial buildings.

The part of the rotor in an electric motor which conveys electric current to the rotor windings.

Statement of dissatisfaction with regards to a service.

Compound gauge
Instrument for measuring pressure.

Compound pump
A rotary pump that has two rotors in series.

Compound refrigerating systems
A system that has several compressors or compressor cylinders in series. The system is used to pump low-pressure vapors to condensing pressures.

Compound wound
Winding used in motors that run on dc current.

Term used to denote increase of pressure on a fluid by using mechanical energy.

Compression chiller
A chiller that achieves the required pressure difference through the use of a compressor.

Compression gauge
Instrument used to measure positive pressures (pressures above atmospheric pressures) only. Gauge dial usually runs from 0 to 300 psig (101.3-2200kPa).

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.

Compression ring
Upper piston ring.

Pump of a refrigerating mechanism that 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, external drive
See Compressor, open type.

Compressor, hermetic
A compressor in which the driving motor is sealed in the same dome or housing as the compressor.

Compressor, multiple-stage
A compressor having two or more compressive steps. Discharge from each step is the intake pressure of the next in series.

Compressor, open
A compressor in which the crankshaft extends through the crankcase and is driven by an outside motor. Commonly called an external drive compressor.

Compressor, reciprocating
A compressor that uses a piston and cylinder mechanism to provide pumping action.

Compressor, rotary
Compressor that uses vanes, eccentric mechanisms, or other rotating devices to provide pumping action.

Compressor seal
Leakproof seal between crankshaft and compressor body in open compressors.

Compressor, single-stage
Compressor having only one compressive step between low-side pressure and high-side pressure.

Series of electrical components which accepts inputs from an operator and controls outputs.

Computer languages
Specific working or codes, such a BASIC, FORTRAN, COBOL, and C, which direct a computer to accept and store information and control outputs.

A fluid formed when a gas is cooled to a liquid state.

Condensate pump
Device to remove water condensate that collects beneath an evaporator.

Liquid or droplets that form when a gas or vapor is cooled below its dew point.

Action of changing a gas or vapor to a liquid.

The part of the refrigeration mechanism which receives hot, high-pressure refrigerant gas from compressor and cools gaseous refrigerant until it returns to its liquid state.

Condenser, air-cooled
Heat exchanger that transfers heat to surrounding air.

Condenser comb
Comb-like device, metal or plastic, used to straighten the metal fins on condensers and evaporators.

Condenser fan
Forced-air device used to move air through air-cooled condenser.

Condenser, water-cooled
Heat exchanger designed to transfer heat form hot gaseous refrigerant to water.

Condensing furnace
High-efficiency, gas forced-air furnace that extracts the latent heat lost in conventional gas forced-air furnaces.

Condensing pressure
Pressure inside a condenser at which refrigerant vapor gives up its latent heat of vaporization 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 vaporization and becomes a liquid. This varies with the pressure.

Condensing unit
The part of the refrigerating mechanism that pumps vaporized refrigerant from the evaporator, compresses it, liquefies it in the condenser, and returns it to the refrigerant control.

Condensing unit service valves
Shutoff valves mounted on the condensing unit to enable service technicians to install and service the unit.

The flow of heat between substances by molecular vibration.

Ability of a substance to transmit heat or electricity.

Substance or body capable of transmitting electricity or heat.

A total unit or system of controls located in one area and enclosed. A window air conditioner is a console air conditioner.

Remains the same; unchanging.

Tube or orifice used to restrict the flow of gas or a liquid.

Substance such as dirt, moisture, or other matter foreign to refrigerant or refrigerant oil system.

Continuous absorption system
System that has a continuous flow of energy input.

Continuous operation
In constant use.

Contractual agreement
A written arrangement, enforceable by law, that is entered into between two parties.

Automatic or manual device used to stop, start, or regulate the flow of gas, liquid, or electricity.

Control, compressor
See Motor control.

Control, defrosting
Device used to automatically defrost the evaporator. It may operate by means of a clock, door cycling mechanism, or during the off cycle.

Control, low-pressure
Cycling device connected to the low-pressure side of system.

Control module
An electrical component used in automotive air conditioning systems to receive sensor input and regulate climate control functions. Also referred to as a microcomputer.

Control, motor
Temperature or pressure-operated device used to control running of motor.

Control point
The condition being maintained by a proportional control.

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 refrigerant into evaporator. Can be a capillary tube, expansion valve, or high-side and low-side float valves.

Control, temperature
Temperature-operated thermostatic device that automatically opens or closes a circuit.

Control system
All of the components required for the automatic control of a process variable.

Control valve
Valve that regulates the flow or pressure of a medium that affects a controlled process. Control valves are operated by remote signals form independent devices using any of a number of control media such as pneumatic, electric, or electrohydraulic.

A group of controls and circuits used to accurately and automatically operate a device.

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.

Heat exchanger that removes heat form a substance.

Cooling coil
Coils cooled by a fluid that does not evaporate (such as brine). The evaporator is sometimes incorrectly referred to as a cooling coil.

Cooling tower
Device that 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 compressor surfaces.

Core, air
Coil of wire not having a metal core.

Core, magnetic
Magnetic center of a magnetic field.

Core valves
Shrader valve used to gain access to a hermetic unit.

Deterioration of materials from chemical action.

The quantity of electricity transferred by and electric current of one ampere in one second.

Counter emf
Tendency for reverse electrical flow as magnetic field changes in an induction coil.

Flow in opposite direction.

Mechanical device joining refrigerant lines.

Cracking a valve
Opening a valve a small amount.

Distance between centerline of main bearing journal and centerline of the crankpin or eccentric.

Crankshaft seal
Leakproof joint between crankshaft and compressor body.

Drawer or compartment in refrigerator designed to provide high humidity along with low temperature to keep vegetables-- especially leafy vegetables--cold and crisp.

Critical pressure
Pressure at which vapor and liquid have same properties.

Critical temperature
Temperature at which vapor and liquid have same properties.

Sealed container of two fluids that, together, create a desired pressure-temperature curve.

Cryogenic Food Freezing
See Fast food freezing.

Cryogenic fluid
A substance that exists as a liquid or gas at temperatures of -250f (-157C) or lower.

Refrigeration that deals with producing temperatures of -250F (-157C) and lower.

Transfer of electrical energy in a conductor by means of electrons changing position.

Current-limiting fuse
A fuse that protects an electrical circuit by limiting the amount of current that flows through it, but does not “blow”.

Current relay
Device that opens of closes a circuit. It is made to act by a change of current flow in that circuit.

Customer relations
The evaluation of the technician by the customer as a result of the technician's job performance and attitudes.

The temperature of pressure at which the control circuit closes.

The temperature or pressure at which the control circuit opens.

A series of events or operations that repeat.

1 - Device that converts fluid power into linear mechanical force and motion. This usually consists of movable elements such as a piston and piston rod, plunger or ram, operating within a cylindrical bore. 2 - Closed container for fluids.

Cylinder, refrigerant
Cylinder in which refrigerant is stored and dispensed . Color code painted on cylinder indicated kind of refrigerant.

Cylinder head
Plate or cap that encloses compression end of compressor cylinder.

Cylindrical commutator
Commutator with contact surfaces parallel to the rotor shaft.