Air Conditioning Info
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Air Conditioner

Equipment that conditions air by cleaning, cooling, heating, humidifying/dehumidifying it. A term often applied to comfort cooling equipment.

Air Conditioning:

A process that maintains comfort conditions in a defined area.

Air-cooled condenser:

A condenser used to reject heat from a refrigeration system into the air

Air Handler:

The device that moves the air across the cooling coil in a forced-air system normally considered to be the fan and its housing.

Air Vent:

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.

Chilled-water 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.

Closed 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.

Condensate pump:

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.

Condensing temperature:

The temperature at which a vapor changes to a liquid.

Condensing unit:

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.

Control system:

A network of controls to maintain desired conditions in a system or space.


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.

Design pressure:

The pressure at which the system is designed to operate under normal conditions.

Dew point:

The exact temperature at which moisture begins to form


A device used in a refrigerant line to remove moisture.

Drip pan:

A pan shaped to collect moisture condensing on an evaporator coil in an air conditioning system.

Dry-bulb temperature:

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 cycle.


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.

Evaporator fan:

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 fluids.


Excess ice or frost accumulation on an evaporator to the point that air flow may be effected.


The trade name for refrigerants.

Full-load amperage(FLA):

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.

Heat exchanger:

A device that transfers heat from one substance to another.

Heat pump:

A refrigeration system used to supply heat or cooling using valves to reverse the refrigerant gas flow.

Hermetic system:

A totally enclosed refrigeration system where the motor and compressor are sealed within the same system with the refrigerant.

High side:

A term used to indicate the high-pressure or condensing side of the refrigeration system.


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.

Latent heat:

Heat energy absorbed or rejected when a substance is changing state and there is no change in temperature.

Leak detector:

Any device used to detect leaks in a pressurized system.

Limit control:

A control used to make a change in a system, usually to stop it when predetermined limits of pressure or temperature are reached.

Liquid line:

A term applied in the industry to refer to the tubing or piping from the condenser to the expansion device.

Liquid slugging:

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.

Low side:

A term used to refer to that part of the refrigeration system that operates at the lowest pressure, between the expansion device and the compressor.

Metering device:

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.

Motor starter:

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.

Noncondensable gas:

A gas that does not change into a liquid under normal operating conditions.

Off cycle:

A period when a system is not operating .

Operating pressure:

The actual pressure under operating conditions.


A small opening through which refrigerant fluid flows.

Overload protection:

A system or device that will shut down a system if an overcurrent exists.


A form of oxygen "03". A layer of ozone in the stratosphere that protects the earth from certain of the sun's ultraviolet wave lengths.

Package unit:

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.

Potential relay:

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.

Pressure switch:

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.

Pump down:

To use a compressor to pump the refrigerant charge into the condenser and/or receiver.


To remove or release fluid from a system.


A component in a refrigeration system for storing and drying refrigerant.

Reciprocating compressor:

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.

Refrigerant reclaim:

Recovering the refrigerant and processing it so that it can be reused.

Refrigerant recovery:

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.

Refrigerant recycling:

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.

Relative humidity:

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.

Remote system:

Often called a split-system where the condenser is located away from the evaporator and /or other parts of the system.

Rotary compressor:

A compressor that uses rotary motion to pump refrigerant vapor/or liquid. It is a positive-displacement pump.

Schrader valve:

A valve similar to the valve on an auto tire that allows refrigerant to be charged or discharged from the system.

Scroll compressor:

A compressor that uses two scroll-type components to compress vapor.

Seal unit:

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.

Sensible heat:

Heat that causes a change in the level of a thermometer (dry bulb).

Short cycle:

The term used to describe the running time (on time) of a unit when it is not running long enough.

Sling psychrometer:

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.

Split system:

A refrigeration or air conditioning system that has the condensing unit remote from the indoor (evaporator coil).

Start capacitor:

A capacitor used to help motor start.

Starting relay:

An electrical relay used to disconnect the start winding in a hermetic compressor.

Starting winding:

The winding in a motor used to primarily to give the motor extra starting torque.

Suction line:

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 compressor.

Super heat:

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 other.

Tons of refrigeration:

12,000 Btu/hr, or 200 Btu per minute.

Total heat:

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.

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

Velocity meter:

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

Water-cooled condenser:

A condenser used to reject heat from a refrigeration system into water


A unit of power applied to electron flow. One watt=3,414 Btu.

Wet-bulb temperature:

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 in evaporation.


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