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  1. #1
    Join Date
    Mar 2016
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    will using existing 6" B vent cause problems

    has anyone ever had a problem increasing to the next size common B vent example Table says 5" common vent will satisfy, will the existing 6" B vent also satisfy? or cause condensation ?

    80K Furnace with 32K water heater type B connectors 18 feet tall Height 3' rise

  2. #2
    Join Date
    Jul 2007
    Location
    Virginia
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    11,844
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    Quote Originally Posted by uncle matt View Post
    has anyone ever had a problem increasing to the next size common B vent example Table says 5" common vent will satisfy, will the existing 6" B vent also satisfy? or cause condensation ?

    80K Furnace with 32K water heater type B connectors 18 feet tall Height 3' rise
    Going strictly by the tables it shouldn’t be an issue, but please note, the venting tables do not guarantee the appliances will vent properly. The tables are simply computer calculations, and not empirical data, from actual tests in a lab under varying conditions.

    The disclaimer on the venting tables states:
    Neither the Gas Research Institute (GRI), members of GRI, nor any person acting on behalf of either, makes any warranty or representation, express or implied, with respect to the accuracy, completeness, or usefulness of this information…………….

    Only measuring draft, draft interference and seeing STABLE CO and O2 numbers from a combustion test will confirm proper venting.
    Instead of learning the tricks of the trade, learn the trade.

  3. #3
    Join Date
    Aug 2002
    Location
    Cincinnati, Ohio
    Posts
    3,048
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    In reality you are less likely to condense in 6" B-vent than in 5".
    captain CO

  4. #4
    Join Date
    Jan 2010
    Location
    CT
    Posts
    35
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    Check the code.

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