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  1. #1

    Furnace intake and exhaust pvc

    My Carrier furnace has two pvc pipes that go through the basement wall and up the side of the house. At the top of the pvc pipe the intake has one 90 degree fitting so the opening is pointed straight out to the side of the vertical pipe. The exhaust pipe has two 90 degree fittings at the top of the pipe, which gives a 180 degree turn and the exhaust opening is pointed straight down. My neighbor says this is the opposite of his and the exhaust opening should point to the side while the intake opening should point down. Can someone tell me which is correct? The furnace was installed before I bought the house, so I don't have a manual and could not find the answer on the net. Thanks.

  2. #2
    Join Date
    Mar 2004
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    Grottoes VA
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    5,856
    Pics would be great.

    It seems from your description you have several problems.
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  3. #3
    Join Date
    Feb 2008
    Posts
    35
    is it the same furnace same spec? hit may differ from one brand to another
    usually the intake is pointing down ans exhaust strait out depending of the snow level anticipation... if you get any in the installation manual it may call for alternate installation or standard installation... need more input.

  4. #4
    Join Date
    Feb 2008
    Location
    harwinton, CT
    Posts
    58

    venting

    most times when venting high efficiency condensing gas furnaces intake will point down and exhaust straight out ... you go up in a gooseneck to be above possible snow line but the final result is still the same intake down and exhaust out... of couse manufacturers secifications will be followed... maybe you can download specs from manufacturer website???

  5. #5
    Join Date
    Nov 2000
    Location
    Eastern PA
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    68,852
    While different brands may have different particulars with venting/combustion air pipe configurations, the end result is always pretty much the same and is dictated by the laws of physics.

    • The flue gas vent termination should be higher then the combustion air inlet.
    • The termination points of the combustion air inlet and the flue gas outlet should be within 14"+- from one another.
    • The flue gas termination should be such that flue gases are not allowed to re-enter the combustion air inlet.
    Earlier Carrier furnaces used to have stainless steel brackets that held the combustion air inlet and flue gas exhaust in exactly the position that Carrier wanted them to be. I don't know if Carrier still uses this bracket, but it sure made it real clear as to how Carrier wanted the termination of the flue vent and combustion air inlet to be run.

    Again, the basics are the same for all brands because all brands must abide by the laws of physics. Some of the particulars are that;

    • Hot air rises, so the flue vent termination should be highest.
    • A pressure zone is created by the flue gas venting that aids in combustion air being allowed back to the furnace as long as the inlet of the combustion air is within the vent's pressure zone. This is why the 14"+- distance between the vent termination and the combustion air termination.
    • Recirculated vent gases are not suitable for combustion air.
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  6. #6
    Join Date
    Jul 2007
    Location
    O'Fallon MO
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    9
    [*]The termination points of the combustion air inlet and the flue gas outlet should be within 14"+- from one another.

    Fuel Gas Code says 18" in the same atmospheric zone, e.g. don't vent out of the roof and drawn from the eve.

  7. #7
    Join Date
    Nov 2000
    Location
    Eastern PA
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    68,852
    Quote Originally Posted by WET BULB View Post
    [*]The termination points of the combustion air inlet and the flue gas outlet should be within 14"+- from one another.

    Fuel Gas Code says 18" in the same atmospheric zone, e.g. don't vent out of the roof and drawn from the eve.
    Don't know what you are referring to as Fuel Gas Code but all manufacturer's specs I have seen state 12-14 inches. This is certainly not something to argue over such minor details, the fact is that the two termination points need to be in the same pressure zone. Hell, could be 24" and everyone is just being cautious.

    This I/O manual for a typical Goodman condensing furnace seems to be looking only at 24" to be the maximum but still gives the general idea of how these terminations should be done. Page 17; http://securenet.goodmanmfg.com/pdf/...it/IO-299B.PDF
    Last edited by RoBoTeq; 02-24-2008 at 04:55 PM.
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  8. #8
    Join Date
    Apr 2004
    Posts
    7,680
    How about a model number?

  9. #9
    My Tempstar 9MPV, 50,000 btu, 92% afu: distance between intake and vent min 8", max 20';on side wall vent and intake openings are 8" min from the wall and openings are min 12" above grade or snow level, vent is straight out and intake shows 90 degree elbow facing down.... on roof same separation distances with openings a min of 12" above the roof or snow level; but, vent is straight up and intake is two 90 elbows with opening facing down.

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