9 - If the common vertical vent is offset, the maximum common vent capacity listed in the common venting tables should be reduced by 20%, the equivalent of two 90° elbows (0.80 x maximum common vent capacity). The horizontal length of the offset shall not exceed 1‐1/2 feet (.46 m) for each inch (25 mm) of common vent diameter.
10- The vent pipe should be as short as possible with the least number of elbows and angles required to com plete the job. Route the vent connector to the vent us ing the shortest possible route.
11- A vent connector shall be supported without any dips or sags and shall slope a minimum of 1/4 inch (6.4 mm) per linear foot (305 mm) of connector, back toward the appliance.
12- Vent connectors shall be firmly attached to the furnace flue collar by
13- When the vent connector used for Category I ap pliances must be located in or pass through a crawl space, attic or other areas which may be cold, that por tion of the vent connector shall be constructed of listed double‐wall type B vent material or material having equivalent insulation qualities.
14- All venting pipe passing through floors, walls, and ceil
ings must be installed with the listed clearance to com bustible materials and be fire stopped according to lo cal codes. In absence of local codes, refer to NFGC (Z223.1).
15 - No portion of the venting system can extend into, or pass through any circulation air duct or plenum.
16 - Vent connectors serving Category I appliances shall not be connected to any portion of mechanical draft systems operating under positive pressure such as Category III or IV venting systems.
17 - If vent connectors are combined prior to entering the common vent, the maximum common vent capacity listed in the common venting tables must be reduced by 10%, the equivalent of one 90° elbow (0.90 x maximum common vent capacity).
18 - The common vent diameter must always be at least as large as the largest vent connector diameter.
19 - In no case, shall the vent connector be sized more than two consecutive table size diameters over the size of the draft hood outlet or flue collar outlet.
20 - Do not install a manual damper, barometric draft regu lator or flue restrictor between the furnace and the chimney.
21 - When connecting this appliance to an existing dedi cated or common venting system, you must inspect the venting system's general condition and look for signs of corrosion. The existing vent pipe size must conform to these instructions and the provided venting tables. If the existing venting system does not meet these re quirements, it must be resized.
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