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  1. #1
    Join Date
    Aug 2007
    Posts
    273

    Use of existing flue to exhaust an infinity condensing gas furnace

    Installer planning to run exhaust up an existing flue which which is not in use. Can a condensing furnace's, infinity 58mvb-100,, exhaust be exited in this manner or must it be exhausted through a wall to work properly . Will it cause a decline in effiency or any other problems thanks ron
    Last edited by ron3637; 11-06-2007 at 01:52 PM. Reason: spelling

  2. #2
    Join Date
    Aug 2007
    Location
    Northern VA 38 degrees N by 76 degrees W
    Posts
    5,062
    Quote Originally Posted by ron3637 View Post
    Installer planning to run exhaust up an existing flue which which is not in use. Can a condensing furnace's, infinity 58mvb-100,, exhaust be exited in this manner or must it be exhausted through a wall to work properly . Will it cause a decline in effiency or any other problems thanks ron
    Answered in your previous post. Yes

  3. #3
    Join Date
    Aug 2007
    Posts
    273

    yes?

    I am a little confused. can you clarify what you mean by yes--It's ok to run the exhaust in the flu's chase or there may be problems thanks ron

  4. #4
    Join Date
    Dec 2006
    Posts
    82
    yes, its ok but your roof might look a little funny with a PVC candy-cane coming out of the chimney...

  5. #5
    Join Date
    Aug 2007
    Posts
    273
    How much will the PVC stick out above the chimmney ? thanks

  6. #6
    Join Date
    Oct 2007
    Location
    Midwest
    Posts
    194
    If they're only running the vent, I thought no elbows were necessary. The inlet would require 180 degrees. Pipe has to be sized properly and possibly insulated depending on length and outdoor temps. Roof venting is recommended by Carrier. Is it going to be a non direct vent 1 pipe? I would be more concerned that they are not getting combustion air from inside the house. See fig. 43 & 44, 24" max height, 12" min. height required above roof,maybe only a few inches above chimney? http://www.docs.hvacpartners.com/idc.../58mvb-1si.pdf

    Don't quote me, I'm not that familar with these.
    Last edited by ZZZRSC; 11-06-2007 at 11:21 PM. Reason: left something out again

  7. #7
    Join Date
    Aug 2007
    Posts
    273
    Is it beter to draw combustion air from inside the house?

  8. #8
    Join Date
    Oct 2007
    Location
    Midwest
    Posts
    194
    I'm sorry I wasn't very clear on that. No, it is better to use outside air. Air in the house has contaminants that might cause problems with these furnaces.

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