The size of the connectors and common segments of multistory venting systems for appliances listed for use with a Type B double-wall gas vent shall be in accordance with Table 803.2(1), provided the following apply:
- The total height (H) for each segment of a multistory venting system is the vertical distance between the level of the highest draft hood outlet or flue collar on that floor and the centerline of the next highest interconnection tee. (See Figure 802.6.4.2)
- The size of the connector for a segment is determined from the appliance's gas input rate and connector rise, and shall not be smaller than the draft hood outlet or flue collar size.
- The size of the common vertical vent segment, and of the interconnection tee at the base of that segment, shall be based on the total appliance's gas input rate entering that segment and its total height. [NFPA 54:18.104.22.168]