Page 2 of 2 FirstFirst 12
Results 14 to 21 of 21
  1. #14
    Join Date
    Sep 2012
    Location
    Framingham, MA
    Posts
    4
    Quote Originally Posted by kangaroogod View Post
    As stated before, hearthman is usually the go to guy for venting questions. I am unclear what he is referring to as a 'shroud' but my thought is that you vent the boiler in schedule 80 PVC which is rated for 200 degrees. This is what most manufacturers are going to in the future in my opinion. Venting under a deck can and likely will cause the deck to rot out. I have seen this firsthand several times. Using the vertical metal piping as a chase way seems the way to go in my opinion but I will reserve the ability to change my mind after hearthman returns
    Is the venting under the deck causing rot due to the vent not extending out from under the deck? Or is it simply because wind, etc can blow back the steam causing eventual rot against the house/deck?

    The hint about schedule 80 pvc is a good one - I was unaware of it. I'm meeting with one of the HVAC contractors hopefully today and I can ask about this.

    Given that there really seem to be two camps (sidewall versus vertical) I'm starting to lean towards sidewall because it's the only option that I can participate in mitigation (i.e., ice removal, etc) if problems develop. I have to imagine that 99.9% of the time there will be no problems with either approach as long as it is properly installed. So I'm trying to resist the urge to over think this issue lest I freeze up unable to make a decision. :-)

  2. #15
    Join Date
    Aug 2004
    Location
    S.E. Pa
    Posts
    6,180
    The combustion fumes must be able to exhaust in the free and clear outdoor air--not trapped up under a deck where it will rot the deck and cause people to slip and fall. You have to plan on drainage so across a wide deck you may not have adequate pitch from one end to the other. A pitch of 1/4" per lineal foot is usually desired but some mfr.s will allow half that. The bottom line is, it has to work and cannot freeze up. Also, you don't want joints where you cannot get to them. If your deck is 18' wide you could route a 20ft length of pipe from the basement-out with no joints under the deck then a discharge elbow or periscope once exposed. Of course, you would have to figure how you are going to support that pipe under the deck every 6 feet.

    A "shroud" in code speak is any covering not meant to be the primary rain cap of a combustion vent. If you ran a chimney liner on a masonry chimney that had a stone stab cap over the liner rain cap, that stone would be treated as an illegal shroud. Often, people put decorative fireplace-type terminations over the listed round termination on liners and vents in an effort to make them more architecturally pleasing but it is wrong.

  3. #16
    Join Date
    Sep 2012
    Location
    Framingham, MA
    Posts
    4
    Quote Originally Posted by hearthman View Post
    The combustion fumes must be able to exhaust in the free and clear outdoor air--not trapped up under a deck where it will rot the deck and cause people to slip and fall. You have to plan on drainage so across a wide deck you may not have adequate pitch from one end to the other. A pitch of 1/4" per lineal foot is usually desired but some mfr.s will allow half that. The bottom line is, it has to work and cannot freeze up. Also, you don't want joints where you cannot get to them. If your deck is 18' wide you could route a 20ft length of pipe from the basement-out with no joints under the deck then a discharge elbow or periscope once exposed. Of course, you would have to figure how you are going to support that pipe under the deck every 6 feet.

    A "shroud" in code speak is any covering not meant to be the primary rain cap of a combustion vent. If you ran a chimney liner on a masonry chimney that had a stone stab cap over the liner rain cap, that stone would be treated as an illegal shroud. Often, people put decorative fireplace-type terminations over the listed round termination on liners and vents in an effort to make them more architecturally pleasing but it is wrong.
    Hi Hearthman,

    Thanks for the reply. My deck is actually elevated about 10 feet off the ground. As such hanging the vent from the joists should not be a problem, nor will pitch and access. I estimate that we'll need about 15-20 feet to make it from the boiler to the edge of the deck where I would like it vented (the corner of the deck nearest the house - we use the deck extensively for plants so I want to minimize any damage to the plants caused by the vent).

    I think I've selected a vendor and he's coming over later today to walk me through the venting options and make a final decision. All of this feedback has been very valuable to help me ask the right questions.

    Thanks!

  4. #17
    Join Date
    Aug 2004
    Location
    S.E. Pa
    Posts
    6,180
    Start with the termination and factor your way back to the house and that will give you the point where it can penetrate the wall.
    HTH,

  5. #18
    Join Date
    Jun 2007
    Location
    Minneapolis, MN
    Posts
    731
    All manufacturers of condensing boilers must have their vent options approved by UL and others. Hence, they are quite specific (see installation manual for the appliance in question) about how the boiler must be vented.

    Most condensing boilers available in the US today may be vented with schedule 40 PVC pipe. As long as the appliance is properly installed and maintained, there is simply no issue with this. We use tile lined and unlined brick chimneys as well as 'B'vent as chases for the normally zero clearance boilers.

    Frosting or frozen exhaust vents are common in some areas under certain conditions, but as long as the vent does not extend through or too far out from an unconditioned space, this is not a typical concern.

    If the condensing boiler you choose if listed with a concentric, coaxial or snorkel (all the same thing) vent kit, then you can use one hole for both fresh air intake and exhaust. This is one of our favorite applications use frequently in our Viessmann Vitodens installations here in Minneapolis.

  6. #19
    Join Date
    Oct 2010
    Location
    Anderson, South Carolina, United States
    Posts
    6,840
    Hearthman, what are we supposed to use to vent condensing boilers/furnaces if not PVC?

  7. #20
    Join Date
    Nov 2011
    Location
    Long Island, NY
    Posts
    280
    I just wish I had a picture of one running.
    Attached Images Attached Images  

  8. #21
    Join Date
    Aug 2004
    Location
    S.E. Pa
    Posts
    6,180
    Right now you can use PVC but if something goes wrong, the pipe mfr will have a way out and blame you for not reading their warnings . Otherwise, you can use AL29-4c stainless or polypropylene both listed to UL 1738 for CAT III and IV venting per the listed instructions of the venting and appliance, going by whichever is more stringent.

Page 2 of 2 FirstFirst 12

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