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  1. #1

    New furnace vent through wall

    I have an 18 year old Lennox gas furnace that vents through a b-vent.
    Also an 18 year old Bradford-White gas water heater that uses the same vent.

    If I replace the furnace with a high efficiency model that vents through the wall:

    The vent pvc pipe would be within 6 horizontal feet of the sliding glass door on the back (west) side of the house. Any chance that the exhaust gas would get into the house through the door? We use that door even in the winter.

    Can the water heater continue to use the b-vent alone? Or would it not produce enough exhaust heat?

    Thanks.

  2. #2
    Join Date
    Aug 2009
    Location
    Michigan
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    88
    The book that comes with the furnace tells the min. clearences. As for the water heater vent pipe (without seeing), I would only be guessing.

  3. #3
    Join Date
    Mar 2010
    Location
    Manassas, VA
    Posts
    61
    In some situations - once you remove the furnace venting that is tied in w/ the water heater venting, you will have an issue with the vent being too large to work with the water heater alone. Without knowing vent size and btu's, it is impossible to answer the question.

    As far as the new pvc venting - make sure there is a permit and it gets inspected. The inspector has the code book saying whether or not it's safe.

  4. #4
    Join Date
    Jul 2010
    Location
    georgia
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    562
    Quote Originally Posted by ziggyhere View Post
    As far as the new pvc venting - make sure there is a permit and it gets inspected. The inspector has the code book saying whether or not it's safe.
    Except the damage is already done and now you have a hole in your wall

  5. #5
    Join Date
    Jul 2010
    Location
    georgia
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    any reason you dont want to vent vertically, like through the roof? I know my furnace had that as the mfg's preferred venting method.

  6. #6
    Quote Originally Posted by b26440510 View Post
    any reason you dont want to vent vertically, like through the roof? I know my furnace had that as the mfg's preferred venting method.
    My understanding is that the new 95% efficiency furnace must vent through the wall, cannot vent vertically.

  7. #7
    Join Date
    Jul 2010
    Location
    georgia
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    562
    Quote Originally Posted by bw77 View Post
    My understanding is that the new 95% efficiency furnace must vent through the wall, cannot vent vertically.
    That would be news to me, but I'm just a homeowner.

  8. #8
    Join Date
    Dec 2010
    Location
    The Quad-Cities area (midwest).
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    2,699
    Quote Originally Posted by bw77 View Post
    My understanding is that the new 95% efficiency furnace must vent through the wall, cannot vent vertically.
    If you don't what the PVC to vent out the side, you can vent them vertically.
    If it can be done (without too much trouble) is a differant issue. That's why most contractors vent horizonally.

  9. #9
    Join Date
    Jul 2004
    Location
    Massachusetts
    Posts
    6,837
    Your installing company should be able to answer these questions for you. Can they not answer them?

  10. #10
    I called the local building office. There is a 4' minimum horizontal clearance required between the vent pipe and the edge of the door.

    I just like to know these things, because sometimes I get different answers from different contractors.

    One guy told me I could continue to vent the water heater up the b-vent, the other guy did not mention that as an option.

  11. #11
    Join Date
    Dec 2010
    Location
    The Quad-Cities area (midwest).
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    2,699
    Quote Originally Posted by bw77 View Post
    I called the local building office. There is a 4' minimum horizontal clearance required between the vent pipe and the edge of the door.

    I just like to know these things, because sometimes I get different answers from different contractors.

    One guy told me I could continue to vent the water heater up the b-vent, the other guy did not mention that as an option.
    If a permit is taken, then, theoretically, it should be installed correctly.
    However, even if they say they are getting a permit doesn't mean it'll be inspected. If I were you I would call for the inspection.
    Depending on the size of the 'B' vent, it should be okay with just the water heater. The rule of thumb (to pass code) for the 'B' vent is 2" larger than the W/H vent, i. e.; 3" W/H vent 5" class b vent.

  12. #12
    Join Date
    Jun 2011
    Location
    Glenrothes, Scotland
    Posts
    45
    High efficiency appliances produce a lot of condensate which can be a nuisance when it plumes outside. Try to make sure that your installer takes this into consideration. Also, if you are going to take the flue through the wall, try to make sure that your guy fits the flue (vent) with a drop back towards the boiler to allow condensate to run backwards to the appliance drain. If possible, I always prefer to fit vertical flues to HE boilers.

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