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  1. #1
    Join Date
    Jun 2019
    Posts
    2
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    Exhaust Pipe move - side porch addition

    Hi all,

    First time poster here looking for some advice. We are wanting to add a side porch to complete a wrap around patio at our house, but the exhaust pipe for our gas furnace is currently outputting into that space. So, I'm looking for some advice from the community. What I would like to do ideally is move the exhaust to the other side of the house. However, the furnace is much closer to the current output area and I fear that a longer exhaust pipe run (it would be 25') may not be ideal and would be cause for concern. I don't like the idea of more potential issues with gas exhaust under the house, but if it is safe to do so I would prefer that to extending the current pipe past the patio as we'd like to enjoy the space in the winter and I fear wind would blow it back into the patio, etc. Would a 25' run for a gas furnace exhaust be safe? I've been nervous with the contractor saying he would find someone to do it for him when the time came but not providing definitive advice and I'm quite concerned about the safety of the exhaust pipe.

    I can provide more info on the model and hopefully pics this evening as I'm sure it would help. It is a 10 year old Lennox gas furnace. I've found the homebuilder basically used bottom of the line for HVAC as we've already replaced both upstairs and downstairs units other than the furnace already last year. So I'm sure least efficient available 10 years ago, single stage, etc. In that regard, if I could solve some of this or minimize risk with a furnace replacement, I would consider options there too. I live in NC.

    Thanks in advance!

  2. #2
    Join Date
    Jun 2012
    Location
    Northern NV
    Posts
    1,701
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    The mfg install instructions will have a vent sizing table with maximum runs and slope to be maintained. If you can stay within those parameters and you insulate the exposed exhaust line, it should be ok. Do you also have a combustion air pipe as well? If so, it also will have to be extended into the same "pressure zone" as the exhaust. Your HVAC professional should be able to find a solution for you that will not compromise the function or safety of the modification.

  3. #3
    Join Date
    Jun 2019
    Posts
    2
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    Thread Starter
    Quote Originally Posted by Juan Madera View Post
    The mfg install instructions will have a vent sizing table with maximum runs and slope to be maintained. If you can stay within those parameters and you insulate the exposed exhaust line, it should be ok. Do you also have a combustion air pipe as well? If so, it also will have to be extended into the same "pressure zone" as the exhaust. Your HVAC professional should be able to find a solution for you that will not compromise the function or safety of the modification.
    Thank you. I will certainly check model this evening and revert back on guidelines and the combustion pipe as I'm not sure there. If I'm unable to go to the other side of the house, are there guidelines for how far past the patio it needs to go? That is more of an industry recommendation than pure by the book. Has anyone done an install this way and if so how did you proceed? Is there any efficiency lost or concerns that should make me consider keeping on this side of the house even if the manual allows for a longer run to the other side?

  4. #4
    Join Date
    Nov 2006
    Location
    Athens, Ohio
    Posts
    6,543
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    It should be vented according to the manufacturer's installation instructions. Then a combustion analysis should be performed to verify proper combustion adjustment and venting.
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