Byrant 90 Plus i Furnaces Install?
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  1. #1
    Join Date
    Jun 2005
    Posts
    40
    Stop by my in-laws home where they are having their two furnaces replaced with Byrant 90 Plus i Furnaces. Because of space limitations, the furnace that serves their upstair is being installed with 2" pipes for the air intake and exhaust, while the furnace for the basement is being exhausted with 2" pipe out the side and drop down flexible ducting to the furnace room for fresh air intake (which will also serve their hot water heater). I was surprised to see the 2" pipe for the basement furance exhaust. I thought that with this setup a 3" inch exhaust pipe was required. Is 2 or 3" the correct size? Thanks

    [Edited by acam on 10-31-2005 at 06:39 PM]

  2. #2
    Join Date
    May 2004
    Location
    Rapid City, SD
    Posts
    7,414
    Depends on the size of the furnace, length of the run and number of elbows used.

    Many many furnaces use 2". Could always dust off the manual and look up the venting tables and get an exact answer. But I wouldn't worry too much about it unless it's a real long run.

  3. #3
    Join Date
    Jun 2005
    Posts
    178
    look in the paper work for the furnace it should tell you what ever the distance is and how many 90 degree angles you can have in that run if it exceeds it you have to go up to 3 inch. and i have never seen flex used for air intake on a 90 plus unit. i think it has to be hard piped to meet code.

  4. #4
    Join Date
    Jun 2005
    Posts
    40

    Run is close to 20 feet

    and goes through their storage room. Does 2" pipe seem appropriate for that length of run?

  5. #5
    Join Date
    Jun 2005
    Posts
    178
    look in the furnace install book it will give you a scale to go by it sounds ok if there is not more elbows than they allow for that run.

  6. #6
    Join Date
    Jun 2005
    Posts
    178
    also 2 45 elbows count as 1 90

  7. #7
    Join Date
    Jun 2005
    Posts
    40

    Code violation?

    Installer says that they have used the air intake method on other application without any problems. The only downside according to them is that you lose some efficiency (e.g. instead of 94%, you get 90-92% with the furnace room drop method). Are the inlaws being conned? Who would they check with to assure code compliance. They are in their late 70's so they don't need any problems, now or especially in January. Thanks

  8. #8
    Join Date
    Oct 2001
    Location
    Waterford Michigan
    Posts
    2,668
    I hope they chose a contractor that pulled a permit.

  9. #9
    Join Date
    Jun 2005
    Posts
    40

    The have a letter

    from the city saying a permit has been pulled. So they are covered there.

  10. #10
    Join Date
    Apr 2001
    Location
    san jose,ca.
    Posts
    5,285
    I`m reading the specs on the 355mav & no where in the specs. vent table is there a mention of drawing comb. area from the area around the furnace. All the vent tables call for 2 pipe system.

  11. #11
    Join Date
    May 2004
    Location
    Rapid City, SD
    Posts
    7,414
    I musta missed that the other furnace is just a 1 pipe system.

    While it'll work fine, it's far better to have a pipe for both intake and exhaust. But in the real world sometimes you just can't get 2 pipes run outside (but thats a very rare case).

    Reguardless whether you use 1 or 2 pipe system, the flex duct that's run for combustion air is a must for the water heater.

  12. #12
    Join Date
    Jun 2005
    Posts
    40

    Now what?

    If it is spec as 2 pipe system only, how should I proceed wtih their installer? Also, what is the downside of doing the install with their method. My father-in-law is not the calmest individual, so before I share what I learned here, I want to get a feel for the options. He one of those people who shots the messenger, so I had better know the options before I approach him.

  13. #13
    Join Date
    Nov 2004
    Posts
    2,927

    condensing furnace

    The code is what the the install book says it is...as far as I know that is true everywhere.

    Ask to talk to the inspectors superior.Explain what you have,and what you want done.

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