Condensing Furnace Flue and Vent question
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  1. #1
    Join Date
    Sep 2012
    Posts
    37

    Condensing Furnace Flue and Vent question

    A couple of questions on venting of condensing furnaces (Trane XV95 in particular):

    1) Where there is a PVC flue pipe brought through the roof, how far above the roof does it need to extend, and should it have a rain cap of some sort?

    2) In my new horizontal attic installation, there's a turbine ("whirllybird") roof vent literally right next to the end of the furnace with the air intake, so there's plenty of fresh combustion air without penetrating the roof. The installer, however, didn't extend the combustion air intake to/through the end (top if it were vertical) of the cabinet. Is this normal/acceptable practice, or should the intake be stubbed outside the cabinet?


    Thanks!

    D.

  2. #2
    Join Date
    Aug 2012
    Location
    North Dakota
    Posts
    518
    In my opinion (or should I say I allways) run both pipes to the outside its a true bennie as far as the exhaust I go one foot above and no rain cap though im not exact on that perticular furnace

  3. #3
    Join Date
    May 2012
    Location
    Upper Michigan
    Posts
    3,588
    It should be 18" above anticipated snow load up north here. The air in the whirly bird wasn't intended for combustion it actually expels heated air.


    Sent from my iPhone using Tapatalk

  4. #4
    Join Date
    Jan 2009
    Location
    Keokuk, IA
    Posts
    5,520
    I've never seen rain caps. No need since it already has drains to accomidate the condensate. Water inside the flue pipe is normal. Not on hte intake however. It need to have a elbow to keep rain out.

  5. #5
    Join Date
    Aug 2007
    Location
    Northern VA 38 degrees N by 76 degrees W
    Posts
    5,058
    Quote Originally Posted by dancaselr View Post
    A couple of questions on venting of condensing furnaces (Trane XV95 in particular):

    1) Where there is a PVC flue pipe brought through the roof, how far above the roof does it need to extend, and should it have a rain cap of some sort?

    2) In my new horizontal attic installation, there's a turbine ("whirllybird") roof vent literally right next to the end of the furnace with the air intake, so there's plenty of fresh combustion air without penetrating the roof. The installer, however, didn't extend the combustion air intake to/through the end (top if it were vertical) of the cabinet. Is this normal/acceptable practice, or should the intake be stubbed outside the cabinet?


    Thanks!

    D.
    Look at your installers guide under venting information highlited,

    NOTE: If only the flue gas pipe is to the outside of the structure a straight section of pipe long enough to exit furnace cabinet must be attached to the inlet air side with an elbow to prevent dust and debris from falling directly into the furnace.

    An object could be placed or fallen against the opening blocking the inlet.

    A concentric kit could be used to make one penetration through the side wall or roof to accomplish what is needed for both intake and exhaust.

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