United CoolAir Glossary
Complete refrigerating system including compressor, condenser and evaporator.
Packaged terminal air conditioning
A combination heating and cooling unit designed for a single room or zone.
Sealing device consisting of soft material or one or more mating soft elements. Reshaped by manually adjustable compression to obtain or maintain a leak Â¬proof seal.
Condition where two or more gases occupy a space and each one creates part of the total pressure.
Parts per million (ppm)
Unit of concentration of one element in another.
Unit of pressure in the metric system.
Pressure imposed upon a fluid is transmitÂ¬ted equally in all directions.
Passive solar heating system
A solar energy system that is dependent upon the radiation striking directly on the surface to be heated.
See Polychlorinated biphenyl.
When direct current is passed through two adjacent metals, one junction will become cooler and the other will become warmer. This principle is the basis of thermoelectric refrigeration.
Material that has its molecules aligned and has its own magnetic field; bar of metal that has been permanently magnetized.
Permanent split capacitor motor
A motor with no relay, in which current flows through both the starting and running winding, making the motor sensitive to line voltage and resulting in low starting torque.
Having openings that allow the passage of liquid or gas.
Measurement of the free hydrogen ion concentration in an aqueous solution. A pH of 7 is neutral.
Distinct functional operation during a cycle.
Phase loss monitor
Motor protection device for polyphase motors that measures current flow to detect phase loss.
Term sometimes used to denote the sensing element on a thermostatic expansion valve.
Physical action wherein an electrical flow is generated by light waves.
Method by which the molecular formaÂ¬tion of an element changes due to light.
Particle of electromagnetic energy found in solar radiation.
See Solar cell.
A type of service valve used on hermetic units.
Property of quartz crystal that causes it to vibrate when a high frequency (500 kHz or higher) voltage is applied. Concept is used to atomize water in a humidifier.
Close-fitting part or plug that moves up and down in a cylinder.
Tube used to measure air velocities.
Constant value (6.626 x 10-34 J.s) which, when multiplied by the frequency of radiation, determines the amount of energy in a photon.
Chamber or container for moving air or other gas under a slight positive pressure.
An air conditioning system in which pneumatic motors are operated by pressurized air lines.
A measure of the amount of pollen in the air.
Polychlorinated biphenyl (PCB)
Dielectric fluid used in capacitors and transformers that is very toxic. Use of PCB in transformers and capacitors is strictly regulated by the Environmental Protection Agency.
Electrical motor designed to be used with a three- or four-phase electrical circuit.
Plastic used as an insulation in some refrigÂ¬erated structures.
Any synthetic rubber polymers produced from the polymerization of an HO and NCO group from two different compounds. Often used in insulaÂ¬tion and molded products.
Flat roof designed to hold a quantity of water, which acts as a cooling device.
Ceramic coating applied to steel surfaces.
Portable service cylinder
Container used to store refrigÂ¬erant. Two most common types are disposable and refillable.
A pressure greater than atmospheric.
Positive temperature coefficient thermistor (PTC)
Electronic thermistor that increases in resistance as temperature increases.
Chemical used in carbon filters to help reduce odors.
Energy related to an object's position.
Electrical switch that opens on high voltage and closes on low voltage.
Electrical force that moves, or attempts to move, electrons along a conductor or resistance.
Instrument for measuring or controlling by sensing small changes in electrical resistance.
Force applied to a 1-lb. mass to give it an acceleration of 32.173 ft./ S2 (gravitational acceleration).
Lowest temperature at which a liquid will pour or flow.
I-Time rate at which work is done or energy emitted. 2-Source or means of supplying energy.
A burner that has air blown into it by a blower.
Sensitive element of a temperatureÂ¬ operated control.
Correction coefficient for the changing current and voltage values of ac power.
Power saver switch
A switch that disconnects heaters in a refrigeration cabinet.
See Parts per million.
Used to cool the refrigerant prior to entering the main condenser.
Energy impact on a unit area; force or thrust on a surface.
Pressure cycling switch
Pressure-controlled switch located on the inlet line of the evaporator to prevent rapid cycling of the compressor.
Pressure difference at two ends of a circuit or part of a circuit.
Loss in pressure due to friction, static head, etc.
Instrument for measuring the pressure exerted by the contents on its container.
Device that remains closed until a certain pressure is reached, then opens and releases fluid to another part of system or breaks an electric circuit.
Pressure motor control
Device that opens and closes an electrical circuit as pressures change.
Pressure regulator, evaporator
Automatic pressure regulating valve mounted in the suction line between the evaporator outlet and the compressor inlet. Its purpose is to maintain a predetermined pressure and temperature in the evaporator.
Switch operated by a change in pressure.
Pressure water valve
Device used to control water flow. It is responsive to head pressure of refrigerating system.
See Absolute pressure.
See Atmospheric pressure.
See Back pressure.
Pressure above atmospheric pressure.
1. Force caused by the weight of a column or body of fluids. 2. High side refrigerant pressure.
Pressure at which a system is operating.
Pressure in low-pressure side of a refrigerating system.
Graph of refrigerant pressure, heat, and temperature properties. (Mollier's diagram).
Pressure-Operated Altitude (POA) valve
Device that maintains a constant low-side pressure, independent of altitude of operation.
In a combustion system, the air mixed with fuel prior to ignition.
A tube-and-fin circular coil that contains a water-glycol solution, which surrounds the ignitor and burner. This coil is used in a water-glycol gas forced-air furnace.
Device that directly controls operation of oil heating system.
Length of tubing fastened to hermetic unit dome, used for servicing unit.
Product heat load
Sum of specific, latent, and respiration heat loads.
Products of combustion
The material produced when a substance is burned.
Volatile hydrocarbon used as a fuel or as a refrigerant.
Being in the proper relative quantity or balance.
Electrical device that will open an electrical circuit if excessive electrical conditions occur.
Particle of an atom with a positive charge.
Pounds per square inch.
Pounds per square inch absolute. Absolute pressure equals gauge pressure plus atmospheric pressure.
Pounds per square inch gauge.
Instrument for measuring the relative humidity of atmospheric air. Also called Wet bulb Hygrometer.
Chart that shows relationship between the temperature, pressure, and moisture content of the air.
See Positive temperature coefficient thermistor.
The ignition of vaporized oil in the firepot.
Flat wheel with a "V" groove. When attached to a drive and drive members, the pulley provides a means for driving a component.
Term referring to one cycle of ignition and combustion of a gas-air mixture in a pulse combustion furnace.
Pulse combustion process
Repeated ignition of a gas and air mixture in a high efficiency gas furnace.
Furnace that has a "tuned" (resonant) combustion chamber. Part of the energy normally lost through the flue is returned to start next "pulse" of combustion.
Anyone of various machines that force gas or liquid into-or draw it out of-something as by suction or pressure.
The act of using a compressor or a pump to reduce the pressure in a container or a system.
Pump that produces fluid velocity and converts it to pressure head.
Pump, fixed displacement
A pump in which the displaceÂ¬ment per cycle cannot be varied.
Pump, reciprocating single-piston
A pump having a single reciprocating (moving up and down or back and forth) piston.
Pump having two interlocking screws rotatÂ¬ing in a housing.
Releasing compressed gas to the atmosphere for the purpose of removing contaminants.
Instrument for measuring high temperatures.