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gas vent exits & re-enters the bldg

D

DWM

Member
Joined
Sep 10, 2012
Messages
13
very unusual inspection. an 80k btu gas fired furnace installed in a bsmnt tenant space in a small hallway betwn a small kitchen and very small bathroom. (no doors) the 6" gas vent exits the building horizontaly, travels 10+ ft and re-enters in the adjacent tenant space, ties into the dbl wall b-vent somewhere in the finished cieling

sorry no pics but i will be drilled for code sections (my books are in MY city vehicle in the shop) any off the top of your head code sections would be greatly appreciated

improper clearance, combustion air,
 
503.6.10 Gas vents serving appliances on more than one floor.

A common gas vent shall be permitted in multistory installations to vent Category I appliances located on more than one floor level, provided that the venting system is designed and installed in accordance with approved engineering methods. For the purpose of this section, crawl spaces, basements and attics shall be considered as floor levels.

503.6.10.1 Appliance separation.

All appliances connected to the common vent shall be located in rooms separated from occupiable space. Each of these rooms shall have provisions for an adequate supply of combustion, ventilation and dilution air that is not supplied from an occupiable space (see Figure 503.6.10.1).
 
I'm assuming it is a fan assisted 80% furnace with other appliances connected to the vent system as well?

504.3.5 Common vertical vent offset. Where the common vertical vent is offset, the maximum capacity of the common vent shall be reduced in accordance with Section

504.3.6. The horizontal length of the common vent offset (Lo) shall not exceed 1 1/2 feet for each inch (18 mm per mm) of common vent diameter (D). Where multiple offsets occur in a common vent, the total horizontal length of all offsets combined shall not exceed 1 1/2 feet for each inch (18 mm per mm) of common vent diameter (D).

This means with a 6" b vent you can have no more than 9' of offset total in the common vent.

504.3.20 Chimney and vent location. Tables 504.3(1), 504.3(2), 504.3(3), 504.3(4) and 504.3(5) shall be used only 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.

A Type B vent shall not be considered to be exposed to the outdoors where it passes through an unventilated enclosure or chase insulated to a value of not less than R8.

Also, if this is a multi story common vent (appliances on more than one level) this section on offsets would apply as well.

504.3.16 Multistory common vent offsets. Offsets in multistory common vent systems shall be limited to a single offset in each system, and systems with an offset shall

comply with all of the following:

1. The offset angle shall not exceed 45 degrees (0.79 rad) from vertical.

2. The horizontal length of the offset shall not exceed

11/2 feet for each inch (18 mm per mm) of common vent diameter of the segment in which the offset is located.

3. For the segment of the common vertical vent containing the offset, the common vent capacity listed in the common venting tables shall be reduced by 20 percent (0.80 × maximum common vent capacity).

4. A multistory common vent shall not be reduced in size above the offset.
 
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