VENTING GUIDELINES FOR CAT E G O RY I GAS APPLIANCES
Venting Guidelines for Category I Gas Appliances Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .2 Definitions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .3 I. Single Appliances . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .3 Notes for Single-Appliance Vent - Tables 1 and 2 . . . . . . . . . . . . . . . . . . .
Venting Guidelines for Category I Gas Appliances Introduction The vent sizing tables in this brochure are part of the National Fuel Gas Code. These tables cover vent sizing for both fan-assisted combustion and draft hood-equipped appliances. Vents for most draft hood-equipped appliances can still be sized based on the draft hood outlet size, or they can be sized using the tables or other engineered methods.
Venting Guidelines for Category I Gas Appliances Definitions 1. Appliance Categorized Vent Diameter/Area — The minimum vent area/diameter permissible for Category I appliances to maintain a nonpositive vent static pressure when tested in accordance with nationally recognized standards. 2. Fan-Assisted Combustion System — An appliance equipped with an integral mechanical means to either draw or force products of combustion through the combustion chamber or heat exchanger. 3.
Venting Guidelines for Category I Gas Appliances Single-Appliance Vent - Tables 1 and 2 (continued) 3. Single-appliance venting configurations with zero (0) lateral lengths in Tables 1 and 2 shall have no elbows in the venting system. For vent configurations with lateral lengths, the venting tables include allowance for two 90-degree turns. For each additional 90-degree turn, or equivalent, the maximum capacity listed in the venting tables shall be reduced by 10 percent (0.90 x maximum table capacity).
Venting Guidelines for Category I Gas Appliances Single-Appliance Vent - Tables 1 and 2 (continued) 10. Vent connectors shall not be upsized more than two sizes greater than the listed appliance categorized vent diameter, flue collar diameter, or draft hood outlet diameter. 11. In a single run of vent or vent connector, more than one diameter and type shall be permitted to be used, provided that all the sizes and types are permitted by the tables. 12.
Venting Guidelines for Category I Gas Appliances Table 1 - Single Appliance Capacity of Type B Double-Wall Vents when connected directly to a Single Category I Appliance Vent Diameter - D Height Lateral H L (ft.) (ft.) 6 8 10 15 20 30 50 100 0 2 4 6 0 2 5 8 0 2 5 10 0 2 5 10 15 0 2 5 10 15 20 0 2 5 10 15 20 30 0 2 5 10 15 20 30 0 2 5 10 15 20 30 50 3 in. 4 in.
Venting Guidelines for Category I Gas Appliances Table 1 - Single Appliance (continued) Capacity of Type B Double-Wall Vents when connected directly to a Single Category I Appliance Vent Diameter - D Height Lateral H L (ft.) (ft.) 6 8 10 15 20 30 50 100 7 0 2 4 6 0 2 5 8 0 2 5 10 0 2 5 10 15 0 2 5 10 15 20 0 2 5 10 15 20 30 0 2 5 10 15 20 30 0 2 5 10 15 20 30 50 10 in.
Venting Guidelines for Category I Gas Appliances Table 2 - Single Appliance Capacity of Type B Double-Wall Vents with Single-Wall Metal Connectors (including AmeriVent listed flexible connector) serving a Single Category I Appliance Vent Diameter - D Height Lateral H L (ft.) (ft.) 6 8 10 15 20 30 50 100 0 2 4 6 0 2 5 8 0 2 5 10 0 2 5 10 15 0 2 5 10 15 20 0 2 5 10 15 20 30 0 2 5 10 15 20 30 0 2 5 10 15 20 30 50 3 in.
Venting Guidelines for Category I Gas Appliances Table 2 - Single Appliance (continued) Capacity of Type B Double-Wall Vents with Single-Wall Metal Connectors (including AmeriVent listed flexible connector) serving a Single Category I Appliance Vent Diameter - D Height Lateral H L (ft.) (ft.) 6 8 10 15 20 30 50 100 9 0 2 4 6 0 2 5 8 0 2 5 10 0 2 5 10 15 0 2 5 10 15 20 0 2 5 10 15 20 30 0 2 5 10 15 20 30 0 2 5 10 15 20 30 50 8 in.
Venting Guidelines for Category I Gas Appliances Examples using Single-Appliance Venting Tables Example 1: Single Draft Hood-Equipped Appliance An installer has a 120,000-Btu/hour input appliance with a 5-inch diameter draft hood outlet that needs to be vented into a 10-foot high Type B vent system.
Venting Guidelines for Category I Gas Appliances Examples using Single-Appliance Venting Tables (continued) Example 3: Interpolating Between Table Values An installer has an 80,000-Btu/hour input appliance with a 4-inch diameter draft hood outlet that needs to be vented into a 12-foot high Type B vent. The vent connector has a 5-foot lateral length and is also Type B. Can this appliance be vented using a 4-inch diameter vent? Solution Table 1 is used in the case of an all Type B vent system.
Venting Guidelines for Category I Gas Appliances Two or More Appliances - Tables 3 and 4 Notes for Multiple-Appliance Vent 1. These venting tables shall not be used where heat reclaimers, draft regulators and vent dampers are installed in the venting system. 2. The maximum vent connector horizontal length shall be 18 inches/inch (180 mm/mm) of connector diameter as follows.
Venting Guidelines for Category I Gas Appliances Two or More Appliances - Tables 3 and 4 (continued) 4. If the vent connectors are combined prior to entering the common vent, the maximum common vent capacity listed in the common venting tables shall be reduced by 10 percent (0.90 x maximum common vent capacity). The length of the common vent connector manifold (LM) shall not exceed 18 inches/inch (180 mm/mm) of common vent connector manifold diameter (D). (See Figure 7.) 5.
Venting Guidelines for Category I Gas Appliances Two or More Appliances - Tables 3 and 4 (continued) 10. The connector rise (R) for each appliance connector shall be measured from the draft hood outlet or flue collar to the centerline where the vent gas streams come together. 11. For multiple units of gas utilization equipment all located on one floor, available total height (H) shall be measured from the highest draft hood outlet or flue collar up to the level of the outlet of the common vent.
Venting Guidelines for Category I Gas Appliances Two or More Appliances - Tables 3 and 4 (continued) 15. Tables 3 and 4 shall be used for chimneys and vents not exposed to the outdoors below the roof line. A Type B vent or listed chimney lining system passing through an unused masonry chimney flue shall not be considered to be exposed to the outdoors. 16.
Venting Guidelines for Category I Gas Appliances Table 3 - Two or More Appliances Capacity of Type B Double-Wall Vents with Type B Double-Wall Connectors serving Two or More Category I Appliances Vent Connector Capacity Vent Height H (ft.) 6 8 10 15 20 30 50 100 Connector Rise R (ft.) 1 2 3 1 2 3 1 2 3 1 2 3 1 2 3 1 2 3 1 2 3 1 2 3 Type B Double-Wall Vent and Connector Diameter - D 3 in. 4 in.
Venting Guidelines for Category I Gas Appliances Table 3 - Two or More Appliances (continued) Capacity of Type B Double-Wall Vents with Type B Double-Wall Connectors serving Two or More Category I Appliances Vent Connector Capacity Vent Height H (ft.) 6 8 10 15 20 30 50 100 Connector Rise R (ft.) 2 4 6 2 4 6 2 4 6 2 4 6 2 4 6 2 4 6 2 4 6 2 4 6 Type B Double-Wall Vent and Connector Diameter - D 12 in. 14 in.
Venting Guidelines for Category I Gas Appliances Table 4 - Two or More Appliances Capacity of Type B Double-Wall Vents with Single-Wall Metal Connectors (including AmeriVent listed flexible connector) serving Two or More Category I Appliances Vent Connector Capacity Vent Height H (ft.) 6 8 10 15 20 30 50 100 Connector Rise R (ft.) 1 2 3 1 2 3 1 2 3 1 2 3 1 2 3 1 2 3 1 2 3 1 2 3 Single-Wall Metal Vent Connector Diameter - D 3 in. 4 in.
Venting Guidelines for Category I Gas Appliances Examples Using Common Venting Tables Example 4: Common-Venting Two Draft Hood-Equipped Appliances A 35,000-Btu/hour water heater is to be common-vented with a 150,000-Btu/hour furnace, using a common vent with a total height of 30 feet. The connector rise is 2 feet for the water heater, with a horizontal length of 4 feet. The connector rise for the furnace is 3 feet, with a horizontal length of 8 feet.
Venting Guidelines for Category I Gas Appliances Examples Using Common Venting Tables (continued) Example 5: Common-Venting a Draft Hood-Equipped Water Heater with a Fan-Assisted Furnace into a Type B Vent In this case, a 35,000-Btu/hour input draft hood-equipped water heater with a 4-inch diameter draft hood outlet, 2 feet of connector rise, and 4 feet of horizontal length are to be common-vented with a 100,000 Btu/hour fan-assisted furnace with a 4-inch diameter flue collar, 3 feet of connector rise, a
Venting Guidelines for Category I Gas Appliances Examples Using Common Venting Tables Summary: 21 (continued) In this example, the installer can use a 4-inch diameter, single-wall metal vent connector for the water heater and a 4-inch diameter, single-wall metal vent connector for the furnace. The common vent should be a 5-inch diameter Type B vent.
Venting Guidelines for Category I Gas Appliances Notes 22
AmeriVent Type B Gas Vent AmeriVent is a complete gas venting system of double-wall pipe and coordinated fittings. With its unique construction and snap-lock connecting method, it is the most efficient, economical and easily installed gas vent system in America. AmeriVent Type B Gas Vent provides a continuous passageway from an approved gas appliance to the termination of the vent above the roof, and requires only 1" clearance to combustible materials.
