Arkansas HVACR NewsMagazine November 2018

S tate, National, Chapter News Tech News

Gas Vent Sizing The proper sizing of gas vents and connectors for furnaces, boilers, and water heaters is very important. Carbon monoxide poisoning, collapsing chimneys, fire hazards, corrosion of vents, draft inducers, heat exchangers, and non-conformance with building codes are all problems associated with gas vent design. There are many terms associated with appliance venting such as flue pipe, flue collar, liners, Type B metal wall pipe, manifolds, vents, and connectors. Good definitions for all these terms and more can be found in this document by Hart & Cooley. From the perspective of the International Fuel Gas Code, which governs the design of venting Category I gas appliances, the two main terms to understand are vents and vent connectors. A vent is the final pathway of the combustion gases to atmosphere. The vent could be a tile lined Masonry chimney, flexible liner inside the chimney or a stand alone Type B metal wall vent. A vent connector is the first pipe leading from an appliance to the vent. A vent

connector can be a single wall metal pipe or a Type B metal pipe. When only a single appliance is being vented and circumstances allow for the vent to be placed directly over the appliance, then no vent connector is needed. The vent simply begins at the appliance flue collar or draft hood and goes straight up. A single appliance will need a vent connector if there is any lateral distance of the appliance from the outlet of the vent. In such a case the vent connector will use elbows to traverse and then connect to the vent. The whole arrangement will appear as a single pipe path, but the vent connector portion can be made of a thin, single wall, 28 gauge metal pipe while the vent portion of the path would have to be a double wall,