United CoolAir Glossary
Fahrenheit scale
Temperature scale with, under standard atmospheric pressure, a water boiling point of 212° and water freezing point of 32°.
Fail-safe control
A device that opens a circuit when a sensing element loses its pressure.
Fan
Radial or axial flow device used for moving or producing flow of gases.
Farad
Unit of electrical capacity. Capacity of a condenser which, when charged with one coulomb of electricity, gives a difference of potential of one volt.
Fast food freezing
Method that uses liquid nitrogen or carbon dioxide to turn fresh food into long lasting frozen food. It is often referred to as Cryogenic Food Freezing.
Fast-acting fuse
A fuse that blows immediately when the rated load is reached.
Feedback
Information on current operation of a system or device used by the control system to modify future operation.
Feedback control system
Control system that is constantly correcting the condition. Also called a "closed loop system."
Female thread
The internal thread on fittings, valves, machine bodies, etc.
Field pole
Part of the motor stator that concentrates the magnetic field of field winding.
Fill (cooling tower)
Material in a cooling tower over which water flows.
Filter
Device for removing small foreign particles from a fluid.
Firepot
Refractory-lined combustion chamber.
Flammability
Tendency to ignite.
Flammable liquids
Liquids having a flash point below 140°F (60°C) and a vapor pressure not exceeding 40 psia (276 kPa) at 100°F (38°C).
Flapper valve
Thin metal valve used in refrigeration compressors that allows gaseous refrigerants to flow in only one direction.
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° 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 the re¬maining liquid refrigerant to the 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.
Flexible duct
A duct that can be routed around obstacles by bending it gradually.
Flexible lines
Lines that provide for easy bending.
Float valve
Type of valve that is operated by a sphere or pan that floats on a liquid surface.
Flooded Condenser
Type of refrigerant system where refrigerant is used to reduce the effective condenser surface, thus maintaining a head pressure for low ambient operation.
Flooded system
Type of refrigerating system in which the liquid refrigerant fills most of the evaporator at all times.
Flooded system, high-side float
Refrigeration system that has a float operated by the level of the high-side liquid refrigerant.
Flooded system, low-side float
Refrigerating system that has a low-side float refrigerant control.
Flow check piston
Piston assembly, with an orifice in the center that can operate as an expansion valve.
Flow Hood
A device used to measure air flow through a register or grille.
Flow meter
Instrument used to measure velocity or volume of fluid movement.
Flue
Gas or air passage that usually depends on natural convection to cause the combustion gases to flow through it. Forced convection may sometimes be used.
Fluid
Substance in either a liquid or gaseous state.
Fluorescent
Capable of exhibiting fluorescence, the emission of electromagnetic radiation of visible light.
Flush
Operation to remove any material or fluids from refrigeration system parts by purging them to the atmosphere using refrigerant or other fluids.
Flux
Substance applied to surfaces to be joined by brazing or soldering to keep oxides from forming.
Foam leak detector
System of soap bubbles or special foaming liquids brushed over joints and connections to locate leaks.
Foaming
Formation of a foam in an oil-refrigerant mix¬ture due to the 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
Accumulated pressure multiplied by an area.
Force-feed oiling
Lubrication system which uses a pump to force oil to surfaces of moving parts.
Forced air
An air conditioning or heating system in which airflow is caused by a fan.
Forced convection
Movement of fluid by mechanical force such as fans or pumps.
Forced-air heating
A heating system that uses a fan to circulate the heated air.
Forced-circulation evaporator
An evaporator that uses a fan to circulate air.
Frame
See Stator.
Free wheeling
Continued rotation of a magnetic clutch on an automotive compressor when the clutch is disengaged.
Freeze drying
Process of food preservation wherein food is frozen and ice content changed rapidly into a vapor, which is then absorbed on an evaporator.
Freeze-up
Formation of ice in the refrigerant control device, which may stop the flow of refrigerant into the evaporator. 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 solid¬ify upon removal of heat. The freezing temperature for water is 32°F (0°C) at atmospheric pressure.
Freezing point depression
Temperature at which ice will form in solution of water and salt.
Friction
Force of resistance produced when two surfaces rub together.
Frost back
Condition in which liquid refrigerant flows from the evaporator into the suction line; usually indicated by sweating or frosting of the suction line.
Frost control, automatic
Control that automatically cycles refrigerating system to remove frost on evaporator.
Frost control, manual
Manual control used to change operation of refrigerating system to produce defrosting conditions.
Frost control, semiautomatic
Control that starts defrost part of a cycle manually and then returns system to normal operation automatically.
Frosting evaporator
Refrigerating system that main¬tains the evaporator at frosting temperatures during all phases of cycle.
Frozen
1-Water in its solid state. 2-Preserved by freez¬ing. 3-Seized (as in machine parts) due to lack of lubrication.
Fuel oil
Kerosene or any hydrocarbon oil as specified by U.S. Department of Commerce Commercial Standard CS12 or ASTM D296, or the Canadian Government Specification Board, 3-GP-28, and having a flash point not less than 100°F (38°C).
Fuel oil distillate
Fuel oil produced through distillation.
Furnace
Self-contained appliance designed to supply heated air through ducts to spaces remote from the appliance location.
Fuse
Electrical safety device consisting of strip of fusible metal in circuit, which melts when the circuit is overloaded.
Fusible plug
Plug or fitting made with a metal of a known low-melting temperature. Used as safety device to release pressures in case of fire.