Page 1 of 2 12 LastLast
Results 1 to 13 of 18
  1. #1
    Hi all,

    This is my first post, I hope I can get some answers here.

    About a week ago, I had a 90% efficiency furnace installed in my attic. It vents horizontally through the sidewall of the house.

    I am very pleased with the contractor and his installation, but I saw one thing that confused me. The vent coming out of the furnace is 2", so the contractor installed a short 2" PVC pipe, then a 2" to 3" transition, and then a 3" PVC pipe which goes to the outside.

    The vent pipe is pitched towards the furnace, as the contractor explained to make any condensate drain towards the furnace and out the drain system. But looking at the horizontal vent pipe, it appears to me that the 2" to 3" transition essentially creates a "step" that the condensate cannot go over, so there will always be a small puddle remaining at the 2" to 3" transition.

    I know it's hard to explain this, but hopefully you can visualize this "step" at the transition.

    My contractor says it's nothing to worry about - would you agree?

    Thanks in advance.



  2. #2
    Join Date
    Apr 2004
    Posts
    7,680
    Yeah, if the pipes never go vertical that can be a problem making that little trap, but it should be somewhat insignificant unless there is no pitch.

    A picture might help.

  3. #3
    Join Date
    Mar 2004
    Location
    SE Michigan
    Posts
    17,598
    I see what your saying. Not sure if it will cause a problem. I have never put the reduceing couplers on the horizontal runs. Cant say that I have seen it done either.
    "The road to Hell is paved with progressive policies."

  4. #4
    Thanks guys!

    I'll try to post a picture straight from the manufacturer's instructions, which shows the setup. The contractor did it exactly this way. I put a red circle around the area where I can see condensate getting trapped. Then again, if the manufacturer shows it this way, it's probably OK?


  5. #5
    Join Date
    Oct 2005
    Location
    Des Moines, Iowa
    Posts
    50
    i dont think there will be a problem, when the furnace kicks on the exhast fan will blow the little bit of water out of the pipe as long as the pipe isn't extreamly sloped or doesnt turn vertical, everything should be fine.

  6. #6
    Join Date
    Feb 2005
    Location
    cincinnati ohio
    Posts
    2,020

    pvc

    When the pipes are horizonal I always wrap the one exhaust with insulation to keep the water from freezing in the off cycle . When they go straight up you can get away with leaving it unwrapped . Bh
    My avatar is a picture of a Goodman Silencer .....These were commonly used in Goodman country ....Photos by hvac tech ( PaysonHVAC )

  7. #7
    If he did it the way the diagram dipicts it, then the forced draft fan will easily ovecome the transition.

    If the 3" pvc is part of the tubing slopin back to the furnace you're still in the clear. If there were an elbow before the furnace than it would be a water trap.
    Yours is not.

    Hope you get alot of years out of it.

  8. #8
    Join Date
    Aug 2004
    Location
    Apex, North Carolina, United States
    Posts
    57
    I have vented several 90% furnaces, when I increase from 2" to 3" , the increaser I use has a flat side to it so the water will not get traped. The picture of the increaser is fine for a vertical install.

  9. #9
    Join Date
    May 2004
    Location
    Rapid City, SD
    Posts
    7,403
    I try to use the eccentric 2-3 increasers when I can, but they are a lil more costly than the standard type (and harder to find). When I do have to increase size (like show) for the bayvent wall term kits, I only use 6" or so of the 3" pipe, and I'm very certain that a tiny bit of water isn't going to hamper the air flow since the rest of the way it 2".

    Also I hardly ever insulate the PVC since its usually ran in conditioned spaces. I do my best to run it in conditioned spaces every chance I get, but if I can't then I insulate the heck of out it.

  10. #10
    OK, I am going to try to post another picture, showing the full vent path as installed, and the alternate one that the contractor proposed for my consideration.

  11. #11
    Here is a crude attempt to show the entire vent path as it is. Comes out of the furnace as a 2" pipe, then 2" to 3" coupling, then two 3" 90's to get it up to the outdoor vent. It is properly pitched back towards the furnace, but still leaves a possible "puddle" within the pipe.

    Also shown is what the contractor says he can do - it consists of 2" pipe, then a 2" 90, and then transitions to the 3" pipe for the rest of the way.

    I like the proposed solution, the only concern is that the furnace instructions say that a 3" vent is required, so the question is how much 2" pipe and how many 2" fittings are allowed before transitioning to the 3" pipe?

    What do you guys think of the proposed solution?


  12. #12
    Join Date
    Mar 2002
    Location
    Gaylord, Michigan
    Posts
    729
    Originally posted by mark johnson
    Here is a crude attempt to show the entire vent path as it is. Comes out of the furnace as a 2" pipe, then 2" to 3" coupling, then two 3" 90's to get it up to the outdoor vent. It is properly pitched back towards the furnace, but still leaves a possible "puddle" within the pipe.

    Also shown is what the contractor says he can do - it consists of 2" pipe, then a 2" 90, and then transitions to the 3" pipe for the rest of the way.

    I like the proposed solution, the only concern is that the furnace instructions say that a 3" vent is required, so the question is how much 2" pipe and how many 2" fittings are allowed before transitioning to the 3" pipe?

    What do you guys think of the proposed solution?


    The alternate is how I install horizontal venting. I think that is the solution. Best to have it fixed, to forgo any possibility of a pressure switch tripping and shutting the unit down.

  13. #13
    Join Date
    May 2001
    Location
    Kansas City
    Posts
    2,729
    I hope it doesn't get to cold where you live or that 90% condensing furnace shouldn't be in an attic if it gets below freezing. Its real hard to keep water from freezing below 32*.

Page 1 of 2 12 LastLast

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •  
Comfortech Show Promo Image

Related Forums

Plumbing Talks | Contractor Magazine
Forums | Electrical Construction & Maintenance (EC&M) Magazine
Comfortech365 Virtual Event