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Glossary
of Heating, Ventilation and Air Conditioning (HVAC) Terms
A
B C D E F G H
I J K L
M N O P
R S T U
V W Z
AFUE
Annual Fuel Utilization Efficiency. A measure of a furnace's heating efficiency.
The higher the AFUE percentage, the more efficient the product. The US
government's established minimum AFUE rating for furnaces is 78%.
Air Handler
The indoor part of a central air conditioning or heat pump system that
moves cooled or heated air throughout the ductwork of your home. An air
handler is usually a furnace or a blower coil.
Air Infiltration
Typically, the passing of air into the house through small cracks
or gaps inherent to the structure. Affected by temperature difference
between the inside and outside of the structure, and air pressure factors
(e.g. wind, the operation of solid fuel appliances or electrical appliances
such as fans).
Air Inlet
The designed port(s) of entry for combustion air in a controlled
combustion, solid fuel burning appliance.
Air Inlet Control
The means by which the amount of air entering the air inlet is
regulated. Also referred to as air control.
Air Supply
Broadly, the air that is supplied to the firebox of the solid
fuel burning appliance.
Air-To-Fuel-Ratio
The ratio of air and fuel, by weight, in a solid fuel appliance.
It should be noted that 1 pound of dry air occupies a volume of 13.315
cubic feet at 70 degrees F. Therefore, 35 pounds of air, the typical amount
of air necessary to burn 1 pound of wood in a fireplace, occupies 466
cubic feet.
Airtight Stove
A stove in which a large fire can be suffocated by shutting the
air inlets, resulting ultimately in a large mass of unburned fuel remaining
in the stove.
Aldehydes
Class of compounds with distinct pungent odor, produced during
incomplete combustion of a fuel gas.
Appliance
A solid fuel burning stove, fireplace, furnace, boiler, water heater,
or cookstove.
Appliance Regulator
The appliance component, usually part of the combination valve,
that maintains constant gas pressure.
Appliance to Flue
Means of venting a solid fuel appliance (including fireplace
inserts) into masonry fireplace chimneys; the stainless steel connector
passes from the appliance to the first fire clay flue liner. Also referred
to as direct connection.
Approved
Acceptable to the authority having jurisdiction
Arch
Curved structural support across the top of an opening.
Ash
Noncombustible solid by product of solid fuel combustion.
Ash Drawer
Receptacle beneath the combustion chamber that catches and contains ashes
until removal.
Ash Trap
Compartment or receptacle behind the combustion chamber that attaches
and contains fly ash removal
Auger
Screw-like or worm gear like device that delivers pellets from
the hopper (or from a cup device) through a tube to the burn pot.
Auger Motor
Electric motor that turns the auger.
Authority Having Jurisdiction
The organization, office, or individual responsible for approving
equipment, installation, or procedure.
B
Vent Gas
Listed, factory-built, double wall metal pipe for venting
appliances with draft hoods and other appliances listed for use with Type
B Gas Vent.
Baffle
An obstructing device or partition in a solid fuel appliance,
used to direct air and heat.
Baffle Plate
A partition inside an appliance to control the flow of direction
of combustion air, flames, or flue gases.
Barometric Draft Control/Regulator
A device designed to prevent excessive draft in a fuel burning
appliance by automatically admitting the appropriate amount of air to
the venting system. Draft regulators are usually installed in chimney
connectors.
Barometric Draft Regulator
Control device installed in chimney connectors to prevent excessive draft.
The installer or appliance operator sets the regulator for the desired
draft, after which the regulator automatically admits room air into the
venting system to maintain desired draft.
Bearing Wall
Wall that supports part of the building weight above it in addition
to its own weight. Opposed to a non bearing wall.
Bio Mass
Renewable organic source of fuel.
Boiler, Hot Water
Central heating appliance for heating water and circulating steam
or hot water to the house through pipes.
Boiler, Steam
A steam central heating appliance
Bottom Feed
Pellet appliance fuel feed design which delivers pellets from
beneath or behind the burnpot. Also known as underfeed and includes side
feed.
Breaching
Horizontal access into a chimney for a chimney connector. In
prefabricated chimneys, a T provides a breaching. In masonry chimneys,
breaching are holes that should have sleeves or liners of tile or heavy
steel.
Btu
British Thermal Unit. That's the amount of heat required to raise one
pound of water by one degree Fahrenheit. What that means is the higher
the Btu rating, the more heating capacity of the equipment.
Btuh
British Thermal Units per Hour - The amount of heat required
to raise the temperature of one pound of water one degree Fahrenheit.
Burn Back
The condition of smoke or of charred, smoldering, or burning
pellets in the hopper
Burn Pot
Metal or ceramic device in the combustion chamber where fuel and air are
mixed and primary combustion occurs.
Burn Rate
Combustion rate, usually expressed in pounds of fuel consumed
per hour.
By-pass Damper
Term specifically referring to the movable plate in catalytic
wood burning appliances which in one position channels the flue gases
through the catalytic combustor. On some non-catalytic appliances, a moveable
plate that redirects and increases residence time of gases.
CAE
Combined Annual Efficiency is a measure of the amount of heat produced
for every dollar of fuel consumed for both home heating and water heating.
Carbon Dioxide
CO2. Colorless, odorless noncombustible gas produced by the complete
combustion of carbonaceous fuel; is nontoxic.
Carbon Monoxide
CO. Colorless, odorless, combustible, and toxic gas produced
by the incomplete combustion of carbonaceous fuel, resulting in the combining
of 1 rather than 2 oxygen atoms with 1 carbon atoms. Deadly to humans.
Cast Iron Stove
A material used in many stoves. Iron is heated to a liquid form and poured
into molds, usually with decorative details.
Catalytic Combustor
Device designed to increase combustion efficiency by lowering
flue gas ignition temperatures. Consists of substrate, washcoat, catalysts
and canning system.
CFM
Cubic feet per minute. A standard measurement of airflow.
Chase
A structure built around, and enclosing portions of chimney exterior
to the house.
Chimney
A portion of the venting system, through which flue gases are
vented to the outdoors and by which penetrated combustible surfaces are
protected; a primarily vertical shaft enclosing at least one flue, the
design of which results in a natural draft.
Chimney Breaching
A means of venting a solid fuel appliance into masonry fireplace chimneys;
the chimney connector passes through the chimney wall to the inside of
the flue liner by means of a thimble or approved pass-through device.
Chimney Capacity
The maximum safe venting capability of a chimney, most often
expressed in terms of the fuel consumption rate of connected appliances
(in btu per hour), but more fundamentally related to the mass flow (e.g.
pounds per minute) of flue gas which will flow up the chimney under given
conditions of temperature and barometric pressure.
Chimney Connector
The portion of the venting system between the appliance and the
chimney. Commonly called stovepipe. Stovepipe is commonly used for chimney
connectors. Some appliances have no connectors because the chimney connects
directly to the appliance. (e.g., many prefabricated fireplaces).
Chimney Fire
The burning of soot/creosote deposits inside a chimney or stovepipe.
Chimney Liner
Usually a high temperature clay round or rectangular sleeve lining
the interior of masonry chimneys. Although not recognized by many building
codes, other materials such as stainless steel stovepipe and enameled
porcelain coated steel industrial chimneys can be used as liners.
Circulating Fireplace
A fireplace with multiple-wall construction around the fire chamber which
permits air to circulate between the walls, become heated, and enter the
house directly or via short ducts.
Circulating Stove
Also see circulating fireplace. A stove with an outer jacked (usually
sheet metal) beyond the main structure, with openings at or near the bottom
and top so that air can circulate between the stove body and its jacket.
For purposes of determining safe clearances, a circulating stove must
be fully jacketed on all four sides, including at the access doors and
on the top.
Clean-out
Opening at base of fireplace for cleaning out ashes.
Clean-out Door
Means for closing and sealing the opening provided for inspection
and removal of creosote and other chimney deposits; should be well sealed
against air infiltration.
Clearances
Minimum distance, composed only of an air space, which must be
maintained between a heat source such as an appliance or vent and combustible
surfaces.
Combination Valve
Gas valve which combines control functions; usually consists
of gas manual valve assembly; pilot safety shutoff system, diaphragm valve,
gas pressure regulator, and valve operator.
Combustible Material
Material made of or surfaced with wood, compressed paper, plant
fibers, or other material that will ignite and burn, as applied to materials
adjacent to or in contact with heat-producing appliances, chimney connectors,
steam and hot water pipes and warm air ducts. Such material shall be considered
as combustible even though flameproof, fire retardant treated, or plastered.
Combustibles
(as applied to walls, floors and ceilings in the context of wood
heater clearances for safety). Constructed of or surfaced with wood, paper,
natural- or synthetic fiber cloth, plastic or other material which will
ignite and burn, whether flame proofed or not and whether plastered or
unplastered. Combustibility is a relative concept. This definition is
adapted from the definition in NFPA booklet glossary of terms relating
to heat-producing appliances.
Combustion
The process of burning, or oxidation accompanied by heat. When
sufficiently rapid, also accompanied by light.
Combustion Air Fan
Electric motor and impellers which supply air to support combustion
of the fuel in the burn pot. May be located ahead (upstream) of the burn
pot and deliver the air under positive pressure, or after (downstream
of ) the burn pot and deliver the air under negative pressure. Usually
provides force to remove byproducts of combustion through the venting
system, but may only provide combustion air.
Combustion Chamber
Area where mixing of combustion air and fuel occurs. Includes
burn pot, refractory panels, and a door with glass.
Combustion Efficiency
The percentage of the total energy content of the fuel consumed that is
converted to heat in the fire.
Combustion Ratio
Required amount of air that must mix with 1 cubic foot of gas
to have complete combustion.
Compression Station
Place where pressure of natural gas is increased before it continues
farther along the pipeline.
Compressor
The part of the outdoor air conditioner or heat pump that compresses and
pumps refrigerant throughout the system.
Condenser
Coil
The outdoor portion of an air conditioning or heat pump system that serves
as a heat transfer point for dispelling heat to the outside air, as in
an air conditioner or heat pump in the summer; or for collecting heat
from the outside air, as in a heat pump in the winter.
Conduction
Direct transfer of heat from one material to another.
Control Board
Integrated, solid state circuit that controls and synchronizes
fuel, combustion air, and convection air delivery.
Control Panel
Contains switches, dials, indicator lights, and possibly adjustment
screws for operating the appliance.
Controlled Combustion
Complete burning of fuel with a steady flame when fuel and air
supplied at proper rate. Contrast with explosion.
Controlled Combustion Appliances
Solid fuel appliances with relatively tight seals. The amount of air entering
the air inlet, thus the combustion rate in the firebox, is operator controlled.
Convection
The transmission of heat by the circulation of a fluid (air or water)
caused by differences in temperature (and therefore density).
Corrosion
The natural process of metal decay. It is hastened by repeated
heating and cooling.
Creosote
Chimney and stove pipe deposits originating as condensed wood
smoke (including vapors, tar and soot). Creosote is often initially liquid,
but may dry or pyrolyze to a flaky or solid form. Smoldering wood (or
coal) is the main source of creosote.
Damper
A valve, usually a moveable or rotatable plate, for controlling
the flow of air or smoke and draft.
Decorative Gas Appliance in a Vented Fireplace
A self-contained, freestanding fuel gas burning appliance designed
for installation only in a vented fireplace and whose primary function
lies in the aesthetic effects of the flame. Gas hearth appliances which
are listed to ANSI Standard Z21.60 include gas log sets.
Diaphragm
Part of pressure regulator which responds to changes in gas pressure
to maintain constant outgoing pressure.
Direct Spark Ignition
A type of intermittent ignition system that ignites the gas directly
at the main burner by means of a spark.
Direct Vent
Method of venting appliance whereby all air for combustion is
derived directly from the outside atmosphere and all flue gases are discharged
directly to the outside atmosphere.
Direct Vent
Exhaust system for gas fireplaces that can be power or gravity
induced. No chimney is required.
Directional Hood
A part of the pilot burner that directs the flame against a control
device and then out across the main burner.
Distillation
Separation of solids and liquids from gases by application of
heat. Method of extracting LPG from wet natural gas.
Downdraft Safety Switch
A feature on gas stoves designed to automatically shut off the
stove if there is a downdraft in the chimney.
Draft
The difference in air pressure at the same elevation between
the inside and the outside of a chimney, chimney connector, or appliance.
The term draft is also sometimes used to denote the rate of combustion
air flow into a fuel-burning appliance, or the rate of flue gas flow.
Draft Hood
A device built into an appliance or made a part of the flue or
vent connector from the appliance designed to (1) provide for the ready
escape of flue gases in the event of no draft, back draft, or stoppage
beyond the draft hood; (2) prevent a back draft from entering the appliance;
and (3) neutralize the effect of stack action of the chimney or gas vent
upon the operation of the appliance. Also known as draft diverter.
Drip
In gas piping, a tee device used to collect condensate from gases.
Installed so that they can be serviced to remove condensate. Also known
as drip leg.
Ductwork
The method by which air is channeled from the furnace or the blower coil
throughout your home.
Efficiency
The percentage of heat that goes into the room instead of up
the chimney. 70-80% efficiency is optimal.
Elbow (Chimney Connector)
The portion of the chimney connector that turns or bends, up
to 90 degrees per elbow. Some types of elbows are adjustable from 90 degrees
to 0 degrees (no bend).
Emissions
Unburned gases and smoke left after combustion.
Energy Efficiency
The percentage of the total energy content of the fuel consumed
that becomes useful heat in the house.
EPA Regulations
Government regulation of woodburning appliances mandating that products
sold after July 1, 1992, emit no more than 4.1 grams of particulate matter
per hour for catalytic equipped units and no more than 7.5 grams for non-catalytic
equipped units.
Ethane
A hydrocarbon compound found in natural gas.
Evaporator
Coil
The part of a heat pump or air conditioning system that is located
inside the house in the air handler. It is here that the refrigerant evaporates
as it absorbs heat from the air that passes over the coil.
Excess Air
Air in the firebox or firechamber of a solid fuel appliance that
is not used in combustion reactions (and exhausts through the venting
system).
Factory-Built Fire Place
Prefabricated metal fire chamber and its chimney, commonly
called zero clearance. Consists of listed manufactured components that
are assembled in accordance with the terms of the listing to form the
completed fireplace.
Factory-Built Chimney
A chimney composed entirely of listed manufactured components,
designed to be assembled as an entire system in accordance with the terms
of the listing.
FAQ
Frequently Asked Question, also used to mean a list of frequently
asked questions.
Fire Resistance
Rating
The time a material will withstand, without igniting, flame and
heat as specified by code and specific test conditions.
Firebrick
Brick capable of withstanding high temperatures, such as in stoves,
furnaces and boilers. Different types of firebrick have different temperature
limits.
Fireclay
A kind of clay capable of withstanding high temperatures while maintaining
its original shape and size; fireclay products are resistant to corrosion,
softening, or cracking. NFPA recommends that fireclay chimney flue liners
resist corrosion, softening, or cracking from flue gases at temperatures
up to 1800 degrees F. Used for flue liners for masonry chimneys.
Fireplace
An enclosure, open in the front for burning fuel. Solid fuel
fireplaces may contain and vent gas log sets or fireplace inserts. Gas
fireplaces are metal appliances open in the front and containing artificial
log sets.
Fireplace Insert
Solid fuel appliance designed to be installed partially or fully in the
firebox of a masonry fireplace, and which vents into the fireplace chimney
by means of full relining or appliance to flue methods.
Fireplace Stove
A freestanding solid fuel burning room heating appliance operated either
with its fire chamber open or closed to the room. NFPA and most codes
use the term room heater-fireplace stove combination for a fireplace stove,
and use the term fireplace stove to designate a unit without doors, that
has its firechamber always open to the room.
Fireplace, Zero Clearance
A factory-built metal fireplace with multi-layer construction providing
enough insulation and/or air cooling so that the base, back, and in some
cases sides, can safely be placed in direct contact (zero clearance) with
combustible floors and walls.
Firestop
A noncombustible barrier, often metal, placed to span the air
space between the outer walls of chimneys and surrounding combustibles;
serves to resist the spread of fire between floors of a structure.
Flagstone
A natural flat stone used in walkways and fireplaces. One stone
is a flag.
Flame Impingement
The striking of flame against an object, such as flame impingement
on the catalytic combustor.
Flame Rectification
Means to ensure gas shutoff in the absence of flame in electronic
ignition systems. Alternating current applied to an electrode engulfed
in the pilot or burner flame is rectified, or changed to direct current,
to power a control module that maintains gas flow until the flame is extinguished.
Flammability Limits
Minimum and maximum amounts of fuel (expressed as a percentage) in an
air and fuel mixture within which combustion can take place.
Flashing
Sheet metal or plastic used at breaks in a a building where water
might leak in. Flashing is run under the building material to create a
barrier.
Floor Protection
Noncombustible material, of specified size, thickness, material
and conductivity placed under a solid fuel appliance; required to extend
beyond the four sides of the appliance. Serves to protect combustible
floor surfaces and framing. Differs from Hearth.
Flue
The passageway in a chimney for conveying flue gases to the outside
atmosphere
Flue Collar
The part of the solid fuel appliance which accepts the chimney
connector. The flue collar diameter or dimension is designed by the appliance
manufacturer to adequately accommodate the flow of gases out of the appliances.
Flue Gases
The gases in an operating venting system, consisting of combustion
products plus whatever air is mixed with them. Essentially synonymous
with smoke and stack gases.
Flue Liner
Usually a high temperature clay (fireclay) round or rectangular
sleeve lining the interior of masonry chimneys. Although not recognized
by many building codes, other materials such as
Fly Ash
Ash that goes up the chimney, as opposed to ash that remains in the fuel
burning appliance.
Freestanding Gas Appliance
An appliance with gas burning log set that has the appearance
of a solid fuel appliance that is placed away from walls in a dwelling.
Freestanding Stove
Heating appliance normally on legs or a pedestal that occupies
an area roughly equal to that of an easy chair.
Full Relining
A means of venting a solid fuel appliance (including fireplace
inserts) into fireplace chimneys; the listed liner extends from the appliance
out the top of the chimney and includes insulation and components in accordance
with the terms of the listing. Also referred to as positive connection.
Furnace
A central heating appliance that supplies hot air, through ducts,
to the house.
Fuse
A device containing an element that protects an electric circuit
by melting to open the circuit when overloaded.
Gas Cock Assembly
Part of the combination valve that is a multi-positioned and tapered
valve designed to allow or shut off gas supply to the appliance. Also
known as valve control.
Gas Fireplace Insert
A gas appliance designed to be installed within an existing fireplace.
Usually gas logs within a metal enclosure that surrounds the logs and
covers the space between itself and the fireplace opening.
Gas Logs
An open flame type appliance consisting of a burner and metal pan or base
supporting simulated logs. May include various ember media.
Gas Vent
A factory made, listed venting system designed to remove flue
gases to the outside atmosphere. See direct vent and Type B vent.
Glass Doors
Used with an open fireplace to reduce draft when fireplace is
not in use. Used with an open fireplace to reduce air flow.
Grate
A metal plate with engineered holes or a framework of metal bars used
to hold fuel in the burnpot and to allow ashes to drop through to the
ash drawer.
Gravity Vent
Type of venting that uses the natural draft of a column of warm gases
rising due to the pressure of surrounding cooler air.
Grounded
The metallic connection of an electric circuit to the earth by means of
a water main or special rod driven into the ground
Hearth
The floor of the firebox, most commonly used in reference to fireplaces.
More generally, the foundation upon which fires for aesthetic and heating
purposes are built. Differs from floor protection. The fire resistant
surface under your stove, often made of brick, or tile.
Heat Exchanger
Located in the furnace, the heat exchanger transfers heat to the surrounding
air, which is then pumped throughout the home.
Hearth
Extension
Noncombustible floor protection extension beyond the opening of a fireplace
or stove. The term is also sometimes used to denote the floor protector
under or around any residential solid fuel burning appliance.
Heat Life (Thermal Capacitance)
The length of time a stove stays hot after burning a load of fuel.
Heat Loss Calculation
Calculation to determine house btu loss; factors include conduction through
construction materials, air infiltration losses and the difference between
actual or projected outside temperatures and desired temperatures inside
the house. Used for determining necessary heat output from the heating
appliance.
Heat Output
The amount of useable heat produced by a heating appliance; expressed
in Btu (for solid fuel and most conventional fuel appliances) or watts
per hour.
Heat Pump
An HVAC unit that heats or cools by moving heat.
Heat Shield
Refers to a noncombustible protector used around appliances,
or smokepipe.
Heat Transfer Efficiency
The percentage of heat, which is released in the fire, that gets
through the appliance and chimney walls to become useful heat in the house.
Heat Value
Amount of heat potential of one cubic foot of gas when burned.
Also known as calorifi value.
High Limit Snap Switch
A control device, or normally closed switch, which shuts down
operation either of all motors or just the auger motor when excessively
high temperatures are reached by opening to interrupt the flow of electrical
current to the component(s).
Hopper
Container attached to an appliance in which fuel, either coal,
nuggets, or wood pellets, is stored and from which the fuel is fed to
the burner.
Hot Air Plenum
Sheet metal chamber mounted to the furnace, into which hot air
is directed, and to which ducts are attached for hot air distribution
into the house.
Hot Junction
Joined, heated end of thermocouple/thermopile.
Hot Surface Ignition
Type of electric (intermittent) ignition system in which a glow
bar is heated by electrical means to a temperature of about 2500 degrees
F. to provide the heat to ignite main burner gas.
HSPF
Heating Seasonal Performance Factor. A measure of heat pump heating efficiency.
The higher the rating, the more efficient the heat pump. The US government's
established minimum HSPF rating for furnaces is 6.8%.
Humidifier
Equipment that injects moisture into heated air as it passes
from the furnace into the ductwork to be distributed throughout the home.
HVAC
Heating, Ventilation, and Air Conditioning.
Ignition
Systems
Devices that ignite the pilot burner and or the main burner
assembly.
Ignition Temperature
The lowest temperature at which combustion occurs. Varies widely
with reference to the variety of flammable gases spontaneously combusting
in a solid fuel appliance.
Incomplete Combustion
Improper air/fuel mixture or inadequate temperatures resulting
in less than complete burning of fuel. May produce aldehydes and or carbon
monoxide.
Increaser
Chimney connector component which permits the transition from
smaller to larger connector, thimble, liner or chimney.
Infrared Radiation
The invisible and harmless radiation emitted by a hot object.
This radiation is converted into heat when it is absorbed.
ISO 9000
A family of international standards for quality management and
assurance.
Insulating
Brick
Low density (high porosity), low thermal conductivity firebrick
intended for use in kilns and furnaces to insulate them, reducing heat
losses. Its conductivity and its heat storage capacity are both 1/5 to
1/3 that of hard firebrick.
Insulation
Material that resists heat flow, used on masonry wall to help
prevent heat loss or heat gain.
Intermittent Ignition System
Means of lighting the pilot or main burner without the use of
a standing pilot, or main burner without the use of a standing pilot,
by electronic spark or hot surface ignition. Also known as electronic
ignition device.
Island Fireplace
Fireplace that has four sides of glass, for viewing from any
angle.
Joint Compounds
Non-hardening materials used on pipe threads to insure a
proper seal.
K Value
Indicates the amount of BTUs of heat that will flow in one hour through
one square foot of a uniform material one inch thick for each degree Fahrenheit
of temperature rise. Used in calculating floor protection materials and
thickness when one noncombustible material is used.
Kindling
Thin, dry wood used to start a fire.
Labeled
Equipment or material identified as having undergone approved
inspection and compliance manufacturing and performance procedures.
Leakage Testing
Procedure to ensure that there is no uncontrolled flow of fuel
gas in the gas piping system and or the appliance.
Lifting Flames
An unstable burner condition in which flames rise above or blow
off the burner port.
Limit Switch
Bimetallic device designed to react to excessive temperature
by causing gas flow to be cut off.
Liquefied Petroleum Gas (LPG)
Colorless, odorless, and nontoxic gas separated from wet natural
gas, light crude oil, and oil refinery gases. Composed predominantly of
following hydrocarbons or mixtures thereof: propane, propylene, normal
butane or isobutane and butylenes.
Liquid Propane
Liquefied petroleum gas, available in cylinders, for home use.
Listed
Included in a list published by a recognized testing laboratory or inspection
agency, indicating that the equipment meets nationally recognized safety
standards.
Low Limit Snap Switch
A control device or normally open switch, which shuts auger and
blower motors down if minimum operating temperatures are not reached or
sustained. Also known as safety disc.
Main Gas Burner
Device for the final conveyance of gas or a mixture of gas
and air to the combustion zone. Consists of burner orifice, air shutter,
mixer, and burner head.
Manifold
The conduit of an appliance which supplies gas to the individual
burners.
Manifold Pressure
Gas pressure between the combination valve and the burner orifice.
Manometer
Instrument used for measuring the pressure of gases.
Mantel
Shelf over and above the fireplace opening. Stone, brick or wood
may be used.
Manufacturers Installation Instructions
Instructions and recommendations for proper assembly, adjustment,
and installation of listed equipment.
Masonry Chimney
Chimney constructed on site of masonry and fire clay materials;
construction requirements specified by code. Also refers to existing masonry
chimneys of various constructions.
Mechanical Draft
duction of combustion air and removal of flue gases by means
of an electric blower
Mechanical Sidewall Venting
Totally horizontal through the wall venting of combustion by products
under positive pressure by means of an electric fan. Commonly referred
to as direct vent, but termination conditions differ. See Direct Vent.
Methane
Main constituent of natural gas. Chemical formula CH4.
Millivolt (MV)
Unit of electromotive force equal to one one-thousandth of a
volt.
Mixer
Component of a main burner where gas mixes with air. Consists
of mixer face, mixer head, and mixing tube (venturi).
Mobile Home Appliance
Solid fuel appliance specifically designed to meet HUD standards
for installation into mobile homes. Includes outside combustion air, floor
mountings, substantially reduced clearances, and designated venting systems.
Moisture Content
The percentage of the fuels weight that is water in comparison
to the total weight of the water and wood in the wet method; in comparison
to the weight of the oven dried fuel in the dry basis.
Multi-meter
A device consisting of one or more meters used to measure two
or more electrical quantities in an electrical circuit, such as voltage,
resistance, and current.
Muriatic Acid
Acid solution used for cleaning masonry work. A solution of hydrochloric
acid.
National Fuel Gas Code (ANSI Z23.1, NFPA 54)
A standard for the installation of gas appliances, piping and venting.
Natural Gas
Colorless, highly flammable gas found in porous geologic formations beneath
the earths surface. Consists mainly of methane.
Odorant
Material added to natural gas or LPG in small concentrations to impart
a delectably distinct odor. Usually mercaptans.
Opacity
Thickness of smoke. An indicator of combustion efficiency.
Orifice
The opening in a cap, spud, or other device whereby the flow of gas is
limited and or controlled and through which the gas is discharged to either
a pilot burner or main burner.
Orifice Spud
A removable plug or cap containing an orifice.
Parging
Process of applying a coat of mortar to masonry construction, especially
used for masonry walls. Also the cement mortar coat itself.
Particulate Matter
Tiny pieces of condensable hydrocarbons in solid or liquid form.
The basis of solid fuel emissions regulations of the Environmental Protection
Agency.
Partition
The masonry wall that must separate flue liners in a masonry chimney.
Also referred to as Wythe.
Penninsula Fireplace
A fireplace that has three sides of glass.
Piezo Ignitor
A device which delivers an igniting spark by means of pressure
on a crystal.
Pilot
A small flame used to ignite the gas at the main burner. May
be standing (constantly burning) or intermittent (on demand for heat).
Plinth
Base-Usually square in shape.
Pointing
Filling mortar into the joint with a trowel after the masonry
units are laid; filling of raked out joints.
Pressure Adjustment Screw
Part of a pressure regulator located directly under a cap screw on top
of the regulator. Means of adjusting gas pressure on some regulators.
Note: some pressure regulators are not subject to adjustment. Check manufacturers
instructions.
Pressure Regulator
A device for controlling and maintaining a uniform outlet gas pressure.
Service regulators reduce high street pressure of natural gas or reduce
LPG storage tank pressure. Appliance regulators, usually part of the combination
valve, reduce, adjust and maintain constant pressure to be used in an
appliance.
Pressure Test
Method of checking for leaks in the gas supply line prior to
installation of appliances
Primary Air
Combustion air directed to the firebox where the fuel is located;
supports all stages of combustion
Primary Combustion
The burning of solid wood and some of the combustible gases, which takes
place in that portion of the appliance where the wood is. The distinction
between primary and secondary combustion is somewhat artificial.
Propane
A colorless, odorless, nontoxic LPG containing more heat value than natural
gas.
PSI
Pounds of pressure per square inch.
Pyrolsis
Chemical alteration of wood, coal, or other combustible materials as a
result of the application of heat. Stage of wood combustion during which
wood molecules decompose into wood oil vapors and gases. The products
of pyrolysis are gases, tar fog and charcoal or coke.
R-Value (Resistance Value)
A measure of how resistant a substance is to transferring heat.
Radiant Stove
A stove whose heat output is mostly in the form of radiant energy. The
exterior of the stove is tremendously hot and room air circulates around
the body of the stove giving off heat.
Radiation
Heat that moves out in waves from a central point and heats objects in
its path. The closer you get to a source of radiant heat the more heat
you will feel.
Reducer
Chimney connector component which permits the transition from a larger
to smaller diameter chimney connector, thimble, liner or chimney. Not
normally recommended because of potential smoke spillage and poor appliance
performance.
Refractory
Any solid ceramic material suitable as a structural or protective material
at high temperatures in a corrosive environment.
Refractory Mortar
High temperature masonry mortar used primarily to join flue liners.
Required by NFPA as medium duty, non water-soluble calcium aluminate refractory
cement mixture, or its equivalent.
Refrigerant
Lines
Two cooper lines that connect the outdoor air conditioner or
heat pump to the indoor evaporator coil.
Reline
An inner chimney made of metal or refractory material, usually with added
insulation, that fits inside an existing chimney. Usually installed for
improved safety and efficiency when a chimney is inappropriate or oversized
for a heating stove.
Residence Time
The amount of time the subject matter remains in the zone of
reference, as in the residence time of gases in the fire chamber.
Safety Pilot Shutoff Valve
A component of the pilot or the combination gas valve that
allows or shuts off gas flow on the basis of the presence or absence of
flame. Consists of a u-shaped electromagnet (see solenoid), gas shutoff
disc, tension spring, keeper plate, thermocouple/thermopile connection,
and a reset button. Also known as millivolt system and electromagnetic
power unit (EPU).
Safety Shutoff
A device, usually powered by a thermocouple/thermopile, designed
to shut off the gas supply to the pilot and or main burner if the source
of ignition fails
Secondary Air
Combustion air directed downstream of the primary combustion
zone (but still in the appliance) to support the combustion of remaining
combustible gases; does not directly influence the rate of primary combustion.
Secondary Combustion
The burning of the combustible gases and smoke which are not
burned in primary combustion.
Secondary Combustion Chamber
The place where secondary combustion occurs.
Sediment Trap
In gas piping, a tee device to intercept or hold solid foreign
particles to prevent them from blocking valves or orifices. If not part
of an appliance, must be installed as close to appliance inlet as possible.
SEER
Seasonal Energy Efficiency Ratio. A measure of cooling efficiency for
air conditioners. The higher the SEER, the more energy efficient the unit.
The government's minimum SEER rating is 10.
Silicone Sealant
Process of sealing cracks with a high temperature silicone sealant.
Single Package
A heating and cooling system contained in one outdoor unit.
Smoke
The visible portion of flue gases composed of solid, liquid and gaseous
products of combustion. Commonly used to refer to all exhaust from solid
fuel burning.
Smoke Chamber
The transition zone between a fireplace throat and fireplace
chimney, extending from the damper or throat to the base of the first
flue.
Smoke Shelf
The ledge directly behind the throat of the fireplace, at the
base of the smoke chamber.
Smoke Test
A test to determine chimney leakage; a small smokey fire is built,
or an activated smoke candle is placed in the appliance after which the
chimney top is obstructed. The smoke is consequently forced through the
chimneys points of leakage. Required by NFPA 211 after construction and
before use of the masonry chimney.
Smoke Test
Checking a masonry fireplace and chimney by building a fire in
the fireplace and closing the flue top. Smoke will flow out of any cracks
or openings.
Soapstone
A metamorphic rock (steatite) known for its ability to withstand direct
flames and to retain heat.
Solenoid
Coil of wire which pulls an iron core within it magnetically when electricity
flows through it. In use, known as electromagnet.
Solid Fuel
Wood, coal, and other similar organic materials in various forms
(e.g. chunk wood, pressed logs, wood pellets, wood chips, paper, processed
coal, coke, peat, charcoal)
Soot
Soft, black or brown velvety deposit of carbon particles inside
appliances, chimneys, and connectors. Soot originates in oxygen-poor flames.
Sour Gas
Gas containing amounts of sulfur that prevent its use as a fuel
unless purified
Spark Arrester
A noncombustible screen installed between the top of the chimney
and the underside of the chimney cap; prevents the escape of sparks and
burning materials from the chimney.
Specific Gravity
The weight of one substance compared to the weight of another
substance, both of equal volume and measured at the same temperature and
pressure.
Spillage
Condition of flue gases failing to exit the venting system properly and
instead slowing out of the relief opening of the draft hood and into the
dwelling. Condition calls for immediate examination of appliance and venting
system and corrective action.
Spillage Test
Method of detecting spillage. Flame or smoke applied at draft hood being
blown out (away from draft hood) indicates spillage problem that should
be remedied with out delay.
Splay
Beveled or sloping surface which terminates a masonry chimney; seals the
flue; provides drainage slope for rain and snow. Also called wash. Recommended
that gap (with flexible sealer) be maintained between flue liner and splay
and that splay extend at least 2 1/2 inches beyond exterior chimney wall.
Split System
A combination heat pump or air conditioner with indoor components such
as a furnace or blower coil. Split systems should be matched for optimum
efficiency.
Stack Effect
The effects resulting from the warm air in buildings on a cold
day being relatively buoyant, just as are the flue gases in a chimney
or stack. Effects include pressure differences between inside and outside
the building, airflow into the building in the lower stories and airflow
out of the building in the upper portions.
Steel Lined Fireplace
Masonry fireplace with prefabricated metal firebox which has
all the components of traditional fireplaces; may have double walls to
provide circulating air passage behind the fire chamber.
Stove
Wood or coal stove. A freestanding solid fuel burning, room heating
appliance intended to be operated with its door(s) closed, i.e. with a
closed fire chamber. NFPA and most codes use the term solid fuel room
heater for stoves.
Stove Board
A prefabricated panel used as a floor or wall protector.
Stove Liner
A layer of metal or brick placed immediately adjacent to a side
or bottom of a stove, intended either to protect the main stove structure
from getting too hot, or to insulate the combustion chamber, making it
hotter and thus promoting more complete combustion. Liners are usually
designed for easy replacement.
Stove Pipe
or smokepipe. Single-walled light gauge (roughly .019 to .024
inches thick) metal pipe generally intended for use as chimney connectors.
Substrate
Catalytic combustor component which carries wash coat and catalyst.
Must be inert, stable, porous material providing large surface area. Almost
exclusively ceramic in solid fuel combustors.
Sweet Gas
Gas in its natural state containing such small amounts of sulfur
that it can be used without purification processes.
Tee
Chimney connector or factory-built chimney component which
provides a 90 degree turn in the venting system; has a removable plate
at the bottom for inspection and chimney cleaning convenience.
Temperature Differential
The difference in temperature between two areas, such as inside and outside
the chimney or house. (Example, if it is 90 degrees F. outside the house
and 70 degrees F. inside the house the temperature differential is 20
degrees F.)
Therm
100,000 British Thermal Units (BTUs)
Thermal Mass
The combination of an objects weight and its ability to absorb heat. Represents
an objects capacity to act as a heat battery.
Thermocouple
A device consisting of two pieces of dissimilar metals joined together
at one end (hot junction). When the hot junction is heated, the thermocouple
produces DC voltage across the other end. Used to power thermoelectric
gas valves.
Thermopile
A number of thermocouples connected in series to produce a higher voltage
than a single thermocouple.
Thermostat
An automatic device for regulating the temperature in a building by controlling
the heating or cooling source or its distribution.
Thimble
A device to be installed in combustible walls, through which stovepipe
passes, intended to help protect the walls from igniting due to stovepipe
heat. A thimble by itself is not usually adequate. The simplest thimbles
are simply metal or fire clay sleeves or cylinders.
Throat
The narrow passage above the fire chamber of a fireplace, forward of the
smoke shelf and below the smoke chamber, generally has a damper which
must be opened before the fireplace is used, and may be closed, when the
fireplace is not in use.
Ton
Unit of measurement for determining cooling capacity. One ton equals 12,000
Btuh.
Type B-W Gas Vent
A listed, factory built, oval shaped, double wall metal pipe for venting
(only) vented wall furnaces.
Unvented Room Heater
Category of unvented, self-contained, free standing, non recessed
(except as noted) fuel gas burning appliance for furnishing warm air by
gravity or fan without duct connection. Gas hearth appliances listed to
ANSI Standard Z21.11.2 include Gas Fireplaces and Fireplace Inserts.
Valve Operator
Part of automatic valve that activates the flow of gas to
the main burner, usually powered electrically. Also known as operator
head.
Vent Orifice
Part of a pressure regulator, located in the chamber above the
diaphragm. An opening which allows for the free flow of air in and out
in the area above the diaphragm. Also provides for the escape of fuel
gas in the event of a diaphragm rupture.
Vented Decorative Appliances
A vented appliance whose only function lies in the aesthetic effect of
the flames. Gas hearth appliances tested to ANSI Standard Z.21.50 include
gas fireplaces, fireplace inserts, and freestanding appliances.
Venting System
A continuous open passageway from the flue collar or draft hood
of the appliance to the outside atmosphere for the purpose of removing
flue gases.
Washcoat
Material applied to the substrate of catalytic combustor
to increase and maintain surface area. Chemically inert, usually a high
surface area alumina.
Water Column (WC)
Measurement in inches of pressure of gas. 28 inches wc equals one psi.
Water Heater
An appliance intended principally for heating domestic (or tap) water.
Wet Gas
Unprocessed natural gas containing more than 20% of impurities
and heavier hydro-carbons
Wythe
The masonry wall that must separate multiple flue liners in a masonry
chimney. Also referred to as Partition.
Zero Clearance Fireplace
A factory built fireplace that is constructed so that it can be placed
safely close to combustible materials.
Zoning
The ability of partitioning a home into various zones, thereby providing
the opportunity to control comfort levels in each zone.
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© Copyright
Lennox Industries Inc., 1999 - 2001
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