AHJ: Authority Having Jurisdiction.
AL29-4C: Stainless Steel formulated to resist corrosion from Category II & IV high efficiency (85% efficient & above) appliances.
ASME: The American Society of Mechanical Engineers.
Ambient Temperature: The temperature surrounding a duct. Example; ambient temperature of 60 degrees plus a temperature rise of 500 degrees allows a true duct temperature of 560 degrees.
Atmospheric Appliance: An appliance which depends on the natural draft created by the chimney or venting system to induce the air required for combustion into the burner.
Aluminized Steel: Steel on which an aluminum surface is electro statically deposited in a process similar to galvanizing.
Available Draft: The draft which may be utilized to cause the flow of air for combustion or the flow of products of combustion.
B Vent: A Metal-Fab venting product with an aluminum inner flue and a galvanized outer casing used on Category I appliances (Also “Big Vent”).
Baffle: A plate or wall for deflecting gases or liquids.
Barometric Damper: A balanced air valve placed so as to admit air to a flue pipe in order to maintain a constant draft through the appliance served by the flue.
Barometric Pressure: Atmospheric pressure as determined by a barometer usually expressed in inches of mercury.
Bell & Socket Connection (also called male/female connection): The diameter of one end of pipe is rolled slightly smaller than the opposite end allowing one piece to be slid into the next piece. This method is employed in Corr/Guard and B Vent.
Big Vent: A Metal-Fab product with the same construction as B Vent in diameters of 14 to 30 inch diameters.
Blower: A fan used to force air under pressure.
Boiler: A closed vessel in which water is heated, steam is generated, steam is superheated, or any combination thereof, under pressure or vacuum by the application of heat from combustible fuels, electricity or nuclear energy.
Boiler Efficiency: The term "boiler efficiency" is often substituted for combustion or thermal efficiency. True boiler efficiency is the measure of fuel-to-steam efficiency.
Boiler Horsepower (BHP, HP): The evaporation of 34-1/2 lbs of water per hour from a temperature of 212 °F into dry saturated steam at the same temperature. Equivalent to 33,475 Btu/hr.
Boiler Rating: The heating capacity of a boiler expressed in boiler horsepower, Btu/hour, or pounds of steam/hour.
Boiler Shell: The outer cylindrical portion of a pressure vessel.
Boiler Water: A term construed to mean a representative sample of the circulating boiler water, after the generated steam has been separated and before the incoming feed water or added chemical becomes mixed with it so that its composition is affected.
Booster Fan: A device for increasing the pressure or flow of a gas.
Breeching: A portion of the system that coveys product of combustion from the appliance(s) to the chimney.
British Thermal Unit (btu): The mean British Thermal Unit is 1/180 of the heat required to raise the temperature of 1 lb of water from 32 °F to 212 °F at a constant atmospheric pressure. A Btu is essentially 252 calories.
Burner: A device for the introduction of fuel and air into a furnace at the desired velocities, turbulence and concentration.
Category I Appliance: Operates with neutral/negative vent static pressure, flue gas temperature does not exceed 550 degrees, and conforms to NFPA 54 & UL 441 (B Vent).
Category II Appliance: Operates with neutral/negative vent static pressure, flue gas temperature is less than 140 degrees (F) above dew point temperature. May cause excessive condensation and conforms to NFPA 211 and UL 1738 (Corr/Guard).
Category III Appliance: Operates at a positive static vent pressure (at the appliance) at a temperature that does not permit condensation. Conforms to NFPA 211 and UL 103 (PIC, IPIC, PSW).
Category IV Appliance: Operates at a positive vent static pressure, flue gas temperature is less than 140 degrees (F) above dew point temperature. May cause excessive condensation and conforms to NFPA 211 and UL 1738 (Corr/Guard).
Centrifugal Fan: Consists of a fan rotor or wheel within a housing that discharges air at a right angle to the axis of the wheel.
Chimney: An enclosed structure containing one or more vertical passageways for conveying flue gases to the outside atmosphere where flue gas temperatures do not exceed 1400 degrees (F) continuous or 1800 degrees (F) intermittent.
Clearance to combustibles: Spacing required (by testing) between flue (when PSW applies) and outer casing to the closest combustible material. Clearances vary from 0 to 18 inches.
CO: Carbon monoxide.
CO2: Carbon dioxide.
Combustible Loss: The loss representing the unused thermal energy occurring through failure to oxidize completely the combustible matter in the fuel.
Combustion: The rapid chemical combination of oxygen with the combustible elements of a fuel resulting in the release of heat.
Combustion Air: Air used in the combustion process.
Combustion Efficiency: The effectiveness of the burner to completely burn the fuel. A well designed burner will operate with as little as 10 to 20% excess air, while converting all combustibles in the fuel to useful energy.
Complete Combustion: The complete oxidation of all the combustible constituents of a fuel.
Condensate: Condensed water resulting from the removal of latent heat from steam. In the case of a high efficiency category II or IV boiler, the condensate is corrosive to 304/316 stainless steel. Corr/Guard is specially designed for category II & IV boilers.
Continuous Enclosure (Aka, Fire Rated Shaft): A mechanical component of a building having a fire resistance rating as required for the structure and whose purpose is to enclose grease duct for its full length to termination.
Corrosion: The wasting away of metal due to chemical action. In a boiler, usually caused by the presence of O2, CO2, or an acid (as produced in high efficiency boilers-see Condensate above).
Corr/Guard: A Metal-Fab product used to vent category II & IV high efficiency appliances. Constructed of AL29-4C (see AL29-4C) stainless steel (aluminized or 430 stainless steel for double wall applications) which inhibits the corrosive effect of the exhaust on high efficiency appliances.
• Small Diameter Corr/Guard 3,4,5 inch
• Large Diameter Corr/Guard 6-24 inch
Dew Point: The temperature at which condensation starts.
Direct Vent: The supply air to the appliance is provided by the space between the inner and outer casing, and the inner flue is used to convey the exhaust gasses to the atmosphere.
Draft: The difference between atmospheric pressure and some lower pressure existing in the furnace stack. The greater the difference in pressure, the better the draft.
Draft Differential: The difference in static pressure between two points in a system.
Draft Hood: Located at the top of the appliance directly under the vent. The draft hood allows dilution air to be introduced into the vent and helps prevent overdraft.
Efficiency: The ratio of output to input.
Field Applied Grease Duct: A grease duct either welded and wrapped or welded and encased in a fire rated shaft.
Firetube: A type of boiler design in which combustion gases flow inside the tubes and water flows around the outsides of the tubes.
Flange Connection: The flat ½ inch surface rolled on the inner flue used to make connection with Metal-Fab PIC, IPIC, and G Series grease duct. A bead of sealant (P071, P077, P080) is applied to the flange and connected using a Vee Band.
Flash Point: The lowest temperature at which a fuel gives off enough vapor to flash into a momentary flame when ignited.
Flue: A passage for products of combustion.
Flue Gas: The product of combustion in the flue to the stack.
Forced-Draft Fan: A fan supplying air under pressure to the fuel burning equipment. Forced-draft is always under positive pressure (see induced draft).
Grease Duct: A sealed passageway carrying grease laden vapors from above a cooking surface to the atmosphere by way of an exhausting fan.
Heat Exchanger: A vessel in which heat is transferred from one medium to another.
Horse Power: 33,475 BTU input is the energy rate needed to evaporate 34.5 lbs of water at 212 degrees (F) in one hour.
IAPMO: International Association of Plumbing and Mechanical Officials.
ICC: International Code Council.
IPIC (Insulated Pressurized Industrial Chimney): A Metal-Fab product used to vent Category III appliances, Type II kitchen hoods and generator exhaust. The inner casing (comprised of 304 or 316 stainless steel) is wrapped with 1, 2 or 4 inches of high density ceramic insulation and enclosed with an aluminized or stainless steel outer casing.
Induced Draft Fan: A fan located within the system or at its termination used to exhaust hot gases from an appliance. Induced draft systems could operate under positive or negative pressure depending on the location of the fan.
K Factor: Resistance to flow.
Make-up Air: Air introduced over a cooking surface to dilute the air containing grease laden vapors and keep the exhaust fan from removing too much conditioned air from the interior space.
Mechanical Draft: The negative pressure created by mechanical means.
NFPA: National Fire Protection Association.
NFPA 37: Standard for the installation and use of stationary combustion engines and gas turbines.
NFPA 54: National Fuel Gas Code.
NFPA 211: Standard for chimneys, fireplaces, vents and solid fuel-burning appliances.
NFPA 96: Standard for ventilation control and fore protection of commercial cooking operations.
NOx: Abbreviation for all nitrogen oxides, a by-product of combustion. As an example, a low NOx appliance is more efficient and generates lower flue gas temperatures.
PIC (Pressurized Industrial Chimney): A Metal-Fab product used to vent Category III appliances, Type II kitchen hoods and generator exhaust. The inner casing (comprised of 304 or 316 stainless steel) incorporates 1 inch of air space covered by an aluminized or stainless steel outer casing.
P071: A Metal-Fab sealant used for applications where the temperatures exceed 600 degrees (F). Used mostly for generator applications.
P077: A Metal-Fab sealant used for applications where the temperatures do not exceed 600 degrees (F). Used mostly for boiler applications.
P080: A Metal-Fab sealant for grease duct applications.
Packaged Boiler: A boiler supplied with all of its components - burner, controls and venting flue, designed as a single engineered package, and ready for on-site installation.
pH: The concentration of a water to denote Acidity or Alkalinity. A pH of 7 is neutral, a pH above 7 denotes alkalinity one below 7 denotes acidity
Power Burner: Refers to a fan internal to the boiler which aids combustion and creates positive pressure at the appliance outlet. These type appliances are normally category III or IV.
Pressure Drop: The difference in pressure between two points in a system caused by resistance to flow.
PSW (Pressurized Single Wall): A Metal-Fab product used to vent Category III appliances, Type I kitchen hoods and generator exhaust, constructed of 304 or 316 stainless steel.
Process Steam: Steam used for industrial purposes other than for producing power.
Refractory Chimney: Masonry chimney used in high heat applications-those that exceed 1400 degrees continuous.
Stack: A vertical conduit, which due to the difference in density between internal and external gases creates a draft at its base. Used interchangeably with “vent & chimney”.
Stack Draft: The differential of the draft measured at the inlet to the stack.
Stack Effect: The difference in elevation of the points of measurement and how the differential effects draft.
Stack Effluent: Gas and solid products discharged from stacks.
• 304: Most common flue material used in Metal-Fab PIC, IPIC, and G Series because of its ease in shaping. Key elements include Chromium, Nickel.
• 316: More corrosion resistant than 304 due to added element molybdenum.
• 430: Highly corrosion and heat resistant. Used only in the outer casing of Corr/Guard.
Thermal Expansion: A change of temperature within a grease duct system that causes the metal surfaces to expand. When heated from ambient temperature to 500 degrees, a duct will expand 2.5 inches in 50 feet.
Thermal Shock: A cycle of temperature swings that result in failure of metal due to expansion and contraction.
Tooless Access Panel: UL listed component allowing access to a grease duct for cleaning. Placement of access panels is dictated by NFPA 96.
UL 103: Standard for safety, factory-built chimneys for residential and building heating appliances.
UL 1738: Standard for safety venting systems for gas-burning appliances, categories II, III, and IV. Requires Metal-Fab Corr/Guard vent.
UL 1978: Test standard for grease ducts; establishes a clearance to combustibles.
UL 2221: Tests fire resistive grease duct enclosure assemblies. A UL 2221 listing is a zero clearance to combustible standard.
UL Listed: Product certification that indicates the product meets safety standards determined by Underwriters Laboratories. (ULC and cUL indicate Canadian requirements.)
U.M.C.: Uniform Mechanical Code
Vee Band: A stainless steel band used to connect two sections of PIC, IPIC, or G Series flue together. A bead of sealant is to be applied on the inner side of the Vee Band, and in the case of generator exhaust, sealant is applied on the top and bottom surfaces between the band and flue.
Vent: A continuous passage from the flue collar to the draft hood. Flue gas temperatures at the outlet do not exceed 600 degrees (F).
Water Column: The amount of pressure necessary to displace a column of water “x” inches. 28 inches of water column equals 1 psi.
Water Tube Boiler: Medium (water, oil) is heated inside tubes surrounded by combustion products.