Face Area: The total plane area of the portion of a grille, coil, or other items bounded by a line tangent
Fahrenheit: A thermometric scale in which 32 (¡F) denotes freezing and 212 (¡F) the boiling point of water under normal pressure at sea level (14.696 psi).
FAIL SAFE - In load management, returning all loads to conventional control during a power failure. Accomplished by a relay whose contacts are normally closed.
FAILURE - A rupture, break, or disintegration of a metal or part of an HVAC system.
FALSE BRINELING - Damage to a solid bearing surface characterized by indentations not caused by plastic deformation resulting from overload, but thought to be due to other causes such as fretting corrosion.
FAN PERFORMANCE CURVE - Fan performance curve refers to the constant speed performance curve. This is a graphical presentation of static or total pressure and power input over a range of air volume flow rate at a stated inlet density and fan speed. It may include static and mechanical efficiency curves. The range of air volume flow rate which is covered generally ex tends from shutoff (zero air volume flow rate) to free delivery (zero fan static pressure). The pressure curves are generally referred to as the pressure-volume curves.
FAN TUBE AXIAL - A propeller or disc type wheel within a cylinder and including driving mechanism supports for either belt drive or direct connection.
FAN, CENTRIFUGAL - A fan rotor or wheel within a scroll type housing and including driving mechanism sup ports for either belt drive or direct connection.
FAN, PROPELLER - A propeller or disc type wheel within a mounting ring or plate and including driving mechanism supports for either belt drive or direct connection.
FAN, VANE AXIAL - A disc type wheel within a cylinder, a set of air guide vanes located either before or after the wheel and including driving mechanism supports for either belt drive or direct connection.
FARAD - A unit of electric capacity, designated by F.
FATIGUE - The phenomenon leading to fracture under repeated or fluctuating stresses having maximum value less than the ultimate strength of the material.
FAULT - A short circuit either line to line, or line to ground.
FEED WATER - Water which is fed to a system such as a boiler or cooling tower.
FEED WATER LINE - The piping leading to a system through which the feed water flows.
FEED WATER HEATER - A device used to heat feed water with steam.
FERRIC COAGULANT - Ferric sulfate Fe2(SO4)3 act to precipitate ferric hydroxide, coagulate at 4.0 - 11.0 pH range.
FERRIC HYDROXIDE - The complete reaction product of iron, water, and oxygen, which forms a red precipitate in water [Fe(OH)3]
FERRIC ION - An iron atom that has a positive electric charge of +3. (Fe2+)
FERROUS - Metallic materials in which the principle component is iron.
FERROUS HYDROXIDE - The reaction product of iron and water in the absence of oxygen; it remains soluble in the water [Fe(OH)2].
FERROUS ION - An iron atom that has a positive electric charge of + 2(Fe2+).
FILMING AMINES - Amines that form a impervious non-wettable film, which acts as a barrier between the metal and the condensate and provide protection against carbon dioxide and oxygen. These amines do not neutralize carbon dioxide.
FILTER - A device to remove solid material from a fluid.
FILTER-DRIER - A combination device used as a strainer and moisture remover.
FILTRATION - Is the process of passing a liquid containing suspended matter through a suitable porous material in such a manner as to effectively remove the suspended matter from the liquid.
FIN - An extended surface to increase the heat transfer area, as metal sheets attached to tubes.
FIRE POINT - The temperature at which a material will continue to burn for at least 5 seconds without the benefit of an outside flame.
FIRE TUBE - A tube, in a boiler, through which the hot gases flow and transfer heat to the water on the outside of the tube.
FIRE WALL - The back end of a boiler, opposite the burner, at which the hot gases change direction of flow.
FIREBRICK - A refractory brick, often made from fire clay, that is able to withstand temperature in the range of 1500 to 1600°C, and is used to line furnaces.
FIXED DISPLACEMENT PUMP - A pump in which the displacement per cycle cannot be varied.
FLASH - The portion of a superheated fluid converted to vapor when its pressure is reduced.
FLASH CHAMBER - A separating tank placed between the expansion valve and the evaporator to separate and bypass any gas formed in the expansion valve.
FLASH GAS - The gas resulting from the instantaneous evaporation of refrigerant in a pressure-reducing device to cool the refrigerant to the evaporating temperature obtaining at the reduced pressure.
FLASH POINT - The temperature at which a material to give off sufficient vapor to form a flammable mixture.
FLASH TANK - A vessel used for separating the liquid phase from the gaseous phase formed from a rise in temperature and/or a reduction of pressure on the flowing stream.
FLASHING - Evaporation of a liquid into a vapor.
FLOCCULANTS - An electrolyte added to a colloidal suspension to cause the particles to aggregate and settle out as the result of reduction in repulsion between particles.
FLOCCULATION - The process of agglomerating coagulated particles into settable flocs, usually of a gelatinous nature.
FLOOD BACK - The condition of liquid refrigerant returning, usually from an overfed evaporator, to the compressor through the suction line.
FLOTATION - A process of separating solids from water by developing a froth.
FLOW RATE - The volume of solution which passes through a given quantity of resin within a given time. Flow rate is usually expressed in terms of feet per minute per cubic foot of resin or as milliliters per minute per milliliter of resin.
FLOW, LAMINAR OR STREAMLINE - Fluid flow in which each fluid particle moves in a smooth path substantially parallel to the paths followed by all other particles.
FLOW, TURBULENT - Fluid flow in which the fluid moves transversely as well as in the direction of the tube or pipe axis, as opposed to streamline or viscous flow.
FLUID - The general term that includes gas, vapor or liquid
FLUID HEAD - The static pressure of fluid expressed in terms of the height of a column of the fluid, or of some manometric fluid, which it would support.
FLUIDIZED BED - A contained mass of finely divided solid that behaves like a fluid when brought into suspension in a moving gas.
FLY ASH - A finely divided siliceous material formed during the combustion of coal, coke, or other solid fuels.
FOAM CARRYOVER - Is the development of excessive moisture in the steam from carryover of foam from the drum. Usually common in low pressure boilers due to high concentration of dissolved solids.
FOAMING - Formation of steam bubbles on the surface of the boiler water due to high surface tension of the water.
FORCE - The action on a body which tends to change its relative condition as to rest or motion.
FORCE PUMP - A device used to inject a solution into a closed system through an opening such as a drain valve.
FORCED CONVECTION - Movement of fluid by mechanical force such as fans or pumps.
FORCED DRAFT COOLING TOWER - Cools water by mechanically forcing air through the tower.
FORCE-FEED OILING - Lubrication system which uses a pump to force oil to surfaces of moving parts.
FOULING - Deposits of impurities, dirt or foreign matter that clog systems or restrict flow and interfere with heat transfer.
FOULING FACTOR - The degree of interference with heat transfer.
FREEBOARD - The space provided above the resin bed in an ion-exchange column to allow for expansion of the bed during backwashing.
FREEZER - A refrigerating device designed to lower the temperature below 0°C.
FREEZER BURN - Condition applied to food which has not been properly wrapped and that has become hard, dry and discolored.
FREEZE-UP - (1) Formation of ice in the refrigerant control device which may stop the flow of refrigerant into the evaporator. (2) Frost formation on an evaporator which may stop the airflow through the evaporator.
FREEZING - Change of state from liquid to solid.
FREEZING POINT - The temperature at which a liquid becomes solid.
FREON - Trade name for a family of synthetic chemical refrigerants.
FRESH WATER - Water that has little or no salt dissolved in it.
FRICTION - Friction is the resistance found at the duct and piping walls. Resistance creates a static pressure loss in systems. The primary purpose of a fan or pump is to produce a design volume of fluid at a pressure equal to the frictional resistance of the system and the other dynamic pressure losses of the components.
FRICTION HEAD - The pressure in psi or feet of the liquid pumped which represents system resistance that must be overcome.
FRIGORIFIC MIXTURE - Are substances used in laboratory methods of producing a drop in temperature. A common example is a mixture of snow and salt.
FROST - Frozen condensation.
FROST BACK - Condition in which liquid refrigerant flows from evaporator into suction line; usually indicated by sweating or frosting of the suction line.
FROST CONTROL - Semiautomatic - Control which starts defrost part of a cycle manually and then returns system to normal operation automatically.
FROST FREE REFRIGERATOR - Refrigerated cabinet which operates with an automatic defrost during each cycle.
FROSTING TYPE EVAPORATOR - Refrigerating system which maintains the evaporator at frosting temperatures during all phases of cycle.
FREQUENCY - The number of vibrations, waves, or cycles of any periodic phenomenon per second. In architectural acoustics, the interest lies in the audible frequency range of 20 to 20000 cps Hertz (cycles per second).
FUEL KNOCK - A hammer like noise produced when fuel is not burned properly in a cylinder.
FULL LOAD CURRENT - See Running Current.
FUMES - Solid particles commonly formed by the condensation of vapors from normally solid materials such as molten metals. Fumes may also be formed by sublimation, distillation, calcinations, or chemical reaction wherever such processes create airborne particles predominantly below one micron in size. Such solid particles sometimes serve as condensation nuclei for water vapor to form smog.
FUNGUS - A lower form of plant life which does not contain chlorophyll, for example, a mold.
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.