GLOSSARY OF TERMS
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Equipment that conditions air by cleaning, cooling, heating, humidifying/dehumidifying
it. A term often applied to comfort cooling equipment.
A process that maintains comfort conditions in a defined area.
A condenser used to reject heat from a refrigeration system into
The device that moves the air across the cooling coil in a forced-air
system normally considered to be the fan and its housing.
A fitting used to vent air manually or automatically.
BTU (British thermal unit):
The amount (quantity of heat required to raise the temperature of
1 lb of water 1 degree F).
An electrical storage device used to start motors (start capacitor)
and to improve the efficiency of motors (run capacitor).
The rating system of equipment used to heat or cool substances.
The quantity of refrigerant in a system.
An air conditioning system that circulates refrigerated water to
the area to be cooled. The refrigerated water picks up heat from
the area, thus cooling the area.
An electron or fluid-flow path that makes a complete loop.
Piping circuit that is complete and not open to the atmosphere.
A vapor pump that pumps vapor (refrigerant or air) from one pressure
level to a higher pressure level.
The moisture collected on an evaporator coil.
A small pump used to pump condensate to a higher level.
Liquid formed when a vapor condenses.
The component in a refrigeration system that transfers heat from
the system by condensing refrigerant.
The temperature at which a vapor changes to a liquid.
A complete unit that includes the compressor and the condensing coil.
A larger version of the relay. It can be repaired or rebuilt and
has moveable and stationary contacts.
A network of controls to maintain desired conditions in a system
A chemical action that eats into or wears away material from a substance.
A component in an air distribution system that restricts airflow
for the purpose of air balance.
To remove moisture from air.
The pressure at which the system is designed to operate under normal
The exact temperature at which moisture begins to form
A device used in a refrigerant line to remove moisture.
A pan shaped to collect moisture condensing on an evaporator coil
in an air conditioning system.
The temperature measured using a plain thermometer.
Electronic air filter:
A filter that charges dust particles using high-voltage direct current
and then collects these particles on a plate of an opposite charge.
Electronic leak detector:
An instrument used to detect gases in very small portions by using
electronic sensors and circuits.
Energy efficiency ratio(EER):
An equipment efficiency rating that
is determined by dividing the output in Btuh by the input in watts.
This does not take into account the startup and shutdown for each
The removal of any gases not characteristic to a system or vessel.
The condition that occurs when heat is absorbed by liquid and it
changes to vapor.
The component is a refrigeration system that absorbs heat into the
system and evaporates the liquid refrigerant.
A forced convector used to improve the efficiency of an evaporator
by air movement over the coil.
The component between the high pressure liquid line and the evaporator
that feeds the liquid refrigerant into the evaporator.
A device that produces a pressure difference in air to move it.
Fan relay coil:
A magnetic coil that controls the starting and stopping of the fan.
A fine mesh or porous material that removes particles from passing
Excess ice or frost accumulation on an evaporator to the point that
air flow may be effected.
The trade name for refrigerants.
The current and electric motor draws while operating under a full-load
condition. also called the run-load amperage.
A safety device used in electrical circuit for the protection of
the circuit conductor and components.
A louvered, often decorative, component in an air system at the inlet
or the outlet of the air flow.
Head pressure control:
A control that regulates the head pressure in a refrigeration or
air conditioning system.
A device that transfers heat from one substance to another.
A refrigeration system used to supply heat or cooling using valves
to reverse the refrigerant gas flow.
A totally enclosed refrigeration system where the motor and compressor
are sealed within the same system with the refrigerant.
A term used to indicate the high-pressure or condensing side of the
A unit equal to 33,000 ft-lb of work per minute.
A control operated by a change in humidity.
Moisture in the air.
Hydro chlorofluorocarbons (HCFC):
Refrigerants thought to contribute to the depletion of the ozone
layer although not to the extent of chlorofluorocarbons.
An instrument used to measure the amount of moisture in the air.
1 kilowatt (1000 watts) of energy used for 1 hour.
Heat energy absorbed or rejected when a substance is changing state
and there is no change in temperature.
Any device used to detect leaks in a pressurized system.
A control used to make a change in a system, usually to stop it when
predetermined limits of pressure or temperature are reached.
A term applied in the industry to refer to the tubing or piping from
the condenser to the expansion device.
A large amount of liquid refrigerant in the compressor cylinder,
usually causing immediate damage.
Locked-rotor amperage (LRA):
The current an electric motor draws or consumed when it is first
turn on. This is normally five times the full-load amperage.
A term used to refer to that part of the refrigeration system that
operates at the lowest pressure, between the expansion device and
A valve or small fixed-size tubing or orifice that meters liquid
refrigerant into the evaporator.
The refrigerant R22.
Motor service factor:
A factor above en electric motor's normal operating design parameters,
indicated on the name plate, under which it can operate.
Electromagnetic contactors that contains motor protection and are
used for switching electric motors on and off .
An inert gas often used to "sweep" a refrigeration system
to help insure that all refrigerant and contaminants.
A gas that does not change into a liquid under normal operating conditions.
A period when a system is not operating .
The actual pressure under operating conditions.
A small opening through which refrigerant fluid flows.
A system or device that will shut down a system if an overcurrent
A form of oxygen "03". A layer of ozone in the stratosphere
that protects the earth from certain of the sun's ultraviolet
An Air conditioning system were all major components are located
in one cabinet.
One distinct part of a cycle.
The part that moves up and down in a compressor cylinder .
A sealed chamber at the inlet or outlet of an air handler. The duct
attaches to the plenum.
A switching device used with hermetic motors that break the circuit
to the start windings after the motor has reached approximately 75%
of its running speed.
A switch operated by a change in pressure.
Abbreviation for pounds per square inch.
Abbreviation for pounds per square inch gage
An instrument for determining relative humidity.
To use a compressor to pump the refrigerant charge into the condenser
To remove or release fluid from a system.
A component in a refrigeration system for storing and drying refrigerant.
A compressor that uses a piston in a cylinder and a back-and-forth
motion to compress vapor.
The fluid in a refrigeration system that changes from a liquid to
a vapor and back to a liquid at certain pressures.
Recovering the refrigerant and processing it so that it can be reused.
To remove refrigerant in any condition from a system and stored
it in an external container without necessarily testing or processing
it in any way.
To clean the refrigerant by oil separation and single or multiple
passes through devices, such as replacesible core filter-dryers,
which reduce moisture, acidity and particulate matter. This term
usually applies to procedures implemented at the job site or at a
local service shop.
The process of removing heat from one place where it is not wanted
and transferring that heat to a place where it makes little or no
difference, ie outside.
The amount of moisture contained in the air as compared to the amount
the air could hold at that temperature.
A small electromagnetic device to control a switch, motor, or valve.
Often called a split-system where the condenser is located away
from the evaporator and /or other parts of the system.
A compressor that uses rotary motion to pump refrigerant vapor/or
liquid. It is a positive-displacement pump.
A valve similar to the valve on an auto tire that allows refrigerant
to be charged or discharged from the system.
A compressor that uses two scroll-type components to compress vapor.
The term used to describe a refrigeration system, including the
compressor, that is completely welded closed. The pressures can be
accessed by saddle valves.
SEER (Seasonal energy efficiency ratio):
This measurement of an air conditioning or heat pump system's energy
efficiency takes into account the cooling efficiency of the system
under various weather conditions. SEER is determined by dividing
the total cooling provided during worm months (in BTU's) by the total
energy (watts-hours) consumed during the same period. The higher
the SEER number the less wattage use per hour.
Heat that causes a change in the level of a thermometer (dry bulb).
The term used to describe the running time (on time) of a unit when
it is not running long enough.
A device with two thermometers, one a wet bulb and one a dry bulb,
used for checking air conditions, temperature, and humidity.
A term used to described the condition when large amounts of liquid
enter a pumping compressor cylinder.
A refrigeration or air conditioning system that has the condensing
unit remote from the indoor (evaporator coil).
A capacitor used to help motor start.
An electrical relay used to disconnect the start winding in a hermetic
The winding in a motor used to primarily to give the motor extra
The pipe that carries the heat-laten refrigerant gas from the evaporator
to the compressor.
Suction service valve:
A manually operated valve with front and back seats located at the
The temperature of vapor refrigerant above its saturation change
of state temperature.
A word used to described the level of heat expressed in Fahrenheit,
ranking, Celsius or Kelvin.
An instrument used to detect differences in the level of heat.
A device that senses temperature change and changes some dimension
or condition within two control and operating device.
Thermostatic expansion valve (TXV):
A valve used in refrigeration systems to control the superheat in
an evaporator by metering the correct refrigerant flow to the evaporator.
Three phase power:
A type of power supply usually used for operating heavy loads. It
consists of the three sine waves that are out of phase with which
Tons of refrigeration:
12,000 Btu/hr, or 200 Btu per minute.
The total amount of sensible heat and latent heat contained in a
substance from a reference point.
A coil of wire wrapped around an iron core that induces a current
to another coil of wire wrapped around the same iron core.
The pressure range between the earth atmosphere and no pressure,
normally expressed in inches of mercury (in.Hg) vacuum pump.
A pump used to remove some fluids such as air and moisture from
a system at a pressure below the earth's atmosphere.
The gaseous state of a
The changing of liquid to a gas or vapor
A meter used to detect the velocity of fluids, air, or water.
Volt-ohm-milliammeter ( VOM):
A multimeter that measures voltage, resistance, and current in milliamperes
The potential electrical difference for electron flow from one line
to another in an electrical circuit
An instrument used to measure electrical potential
A condenser used to reject heat from a refrigeration system into
A unit of power applied to electron flow. One watt=3,414 Btu.
A wet-bulb temperature of air is used to evaluate the humidity in
the air. It is obtained with a wet thermometer bulb to record the
evaporation rate with an air stream passing over the bulb to help
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