Test Standard: UL1738

Scope: These requirements cover venting systems intended for venting Category II, III, or IV gas-burning appliances as defined by the Standard for Gas-Fired Central Furnaces (except Direct-Vent Central Furnaces), ANSI Z21.47 and the National Fuel Gas Code, NFPA 54. Venting systems covered by these requirements are intended to be used with Category II, III, and IV appliances that have been installed in accordance with NFPA 54, and with codes such as the BOCA National Mechanical Code, the Standard Mechanical Code, the Uniform Mechanical Code, and local codes.

Application: ANSI Z21.13/Z21.10 appliances, CONDENSING (85% or more efficiency), OR NON-CONDENSING (84% or less efficiency) appliances, and Listed gas appliances specified for use with Categories II, III, and IV or per appliances installation instructions.
Maximum Gross Stack/Vent temperature: Steel 550° F (boilers or water heater), Polypropylene 230° F (water heater only)

Stack/Vent system pressure: Positive (3” W.C. and Up), Neutral, and Negative

General Constructions: Steel – Inner (AL294C/Duplex stainless), Insulation (1” air), Jacket (stainless steel outer), note some come with aluminized or galvanized jackets, not a good idea. Polypropylene – Polypropylene, single wall only

Sizing: Per appliance’s installation instructions (equivalent feet or NFPA 211 or NFPA 54)