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How not to vent a Gas condensing boiler

Comments

  • SuperTech
    SuperTech Member Posts: 1,579
    Lol. It just needs a little more RTV
  • Jean-David Beyer
    Jean-David Beyer Member Posts: 2,665
    Do not gas condensing boilers require two "vents," one for air supply and one for exhaust, so that the differential pressure between them is extremely low?
  • nibs
    nibs Member Posts: 462
    My Rinnai E50 allows for using room air.
  • Steamhead
    Steamhead Member Posts: 14,338
    Once again- you can't fix stupid!
    All Steamed Up, Inc.
    Steam, Vapor & Hot-Water Heating Specialists
    Oil & Gas Burner Service
    Consulting
    Ironman
  • Ironman
    Ironman Member Posts: 6,323
    Are you kidding? What idiot did this?
    Bob Boan
    You can choose to do what you want, but you cannot choose the consequences.
  • JUGHNE
    JUGHNE Member Posts: 8,175
    Any pictures of the rest of the install?
    Homeowner job?
  • EBEBRATT-Ed
    EBEBRATT-Ed Member Posts: 8,540
    edited January 2019
    Probably not a homeowner. Most of them have more sense.
    RTV coated flue. Must be a new design.

    I am surprised the off gassing from the curing RTV didn't take someone out.
  • Grallert
    Grallert Member Posts: 491
    I think that Viessmann allows for room air, I guess that's why the cover is off.
  • Leonard
    Leonard Member Posts: 903
    edited January 2019
    that RTV burns,

    not knowing any better I used it to line a rusted exhaust suction fan cavity on a Carrier nat gas flat roof HVAC unit we owned. When I tested it red hot burning bits of red "fire-proof" RTV blew out........ I replaced it.
  • Do not gas condensing boilers require two "vents," one for air supply and one for exhaust, so that the differential pressure between them is extremely low?

    Grallert said:

    I think that Viessmann allows for room air, I guess that's why the cover is off.

    They could also have removed one or two of the rubber flaps on top of the boiler to allow air in.
    Often wrong, never in doubt.
    rwhtg
  • mikeg2015
    mikeg2015 Member Posts: 1,181
    edited February 2019

    Do not gas condensing boilers require two "vents," one for air supply and one for exhaust, so that the differential pressure between them is extremely low?

    We use room air on most install of furnaces and boilers unless it’s a very tight home. Too many service calls for plugged intakes to make it worth the minimal impact or the cost of extra piping. Code requires it on some cases.

    But code book writers and inspectors don’t have to clear frozen intakes when it’s -15F outside in 2’ of snow.
  • NY_Rob
    NY_Rob Member Posts: 1,370
    edited February 2019
    If you're venting with PVC and are in an area where snow buildup/blockage is a concern, you could always install a Cleanout Tee with Cap in the intake piping and just remove the cap for as long as needed if it becomes necessary. No going outside to shovel.

    FWIW- I have read regarding mod-cons that it desirable to use outdoor air for combustion vs. indoor air whenever possible because the outdoor air is generally "cleaner".

    https://www.supplyhouse.com/Spears-P444X-030-3-PVC-DWV-Cleanout-Tee-w-Standard-Plug



    mikeg2015
  • mikeg2015
    mikeg2015 Member Posts: 1,181
    Outdoor air is cleaner so long as there’s no grass clippings. But lint and dust would be less and chemicals depending on location. Downside is bugs getting in. We’ve just found we have dramatically fewer issues using indoor air all around and of course you can offer a slightly lower installed price.

    The clean out is a good idea on longer runs.
  • Slimpickins
    Slimpickins Member Posts: 323
    When it says it allows room air you first have to do the math and determine if you have enough cubic feet to allow it. You're really doing your customer a dis-service by not bring intake air into the appliance unless it's absolutely impossible.
    Alan Muller
  • Leonard
    Leonard Member Posts: 903
    Seems a plus to using interior air in cellar is ventilation ..... if have radon, mustiness, etc......
  • ChrisJ
    ChrisJ Member Posts: 11,492
    edited February 2019
    Not that I'm defending this disaster but most red RTVs are rated to be used at 600 degrees F and the only "off gassing" would be acedic acid which smells like vinegar from the RTV curing. Once cured I wouldn't expect any smell.


    I wouldn't think you would be venting at 600+ into that vent.

    Like I said, not defending anything in that picture.
    Single pipe quasi-vapor system. Typical operating pressure 0.14 - 0.43 oz. EcoSteam ES-20 Advanced Control for Residential Steam boilers. Rectorseal Steamaster water treatment
    rick in Alaska
  • mikeg2015
    mikeg2015 Member Posts: 1,181

    When it says it allows room air you first have to do the math and determine if you have enough cubic feet to allow it. You're really doing your customer a dis-service by not bring intake air into the appliance unless it's absolutely impossible.

    It’s not a disservice if there are fewer call backs that way. These are not tight construction cookie cutter modern homes.

    That combustion air gets heated regardless of where its introduced, direct or indirectly. So there no change to net system efficiency.

    We use 2 pipe where it’s nessesary. Most of these installs were previously B vent or chimney vent furnaces at one time, and most were just gravity coal furnaces before that.
  • plumbbob
    plumbbob Member Posts: 16
    whats wrong with it it looks great :)
  • Timco
    Timco Member Posts: 3,025

    Can I play?
    Just a guy running some pipes.
    Intplm.Zman
  • Timco
    Timco Member Posts: 3,025

    I'll add this beauty....
    Just a guy running some pipes.
    rick in AlaskaZman
  • Jean-David Beyer
    Jean-David Beyer Member Posts: 2,665
    And the inspector passed this?
  • ChrisJ
    ChrisJ Member Posts: 11,492
    > @Jean-David Beyer said:
    > And the inspector passed this?

    That's a 50 50.

    Are you surprised if one did?
    Single pipe quasi-vapor system. Typical operating pressure 0.14 - 0.43 oz. EcoSteam ES-20 Advanced Control for Residential Steam boilers. Rectorseal Steamaster water treatment
  • Leon82
    Leon82 Member Posts: 684
    > @Timco said:
    > I'll add this beauty....

    Is the intake teed into the exhaust?
  • Leon82
    Leon82 Member Posts: 684
    It's like they saw a diagram of the concentric vent and moved it to there.

    That couldn't have run more than a few seconds before it started convulsing
  • mikeg2015
    mikeg2015 Member Posts: 1,181
    Leon82 said:

    It's like they saw a diagram of the concentric vent and moved it to there.



    That couldn't have run more than a few seconds before it started convulsing

    You think they opened the manual?


    Easy fix since it’s not newer tight construction. Just make it 1 pipe.... assuming HTP/Westinghouse allows that.
  • Jean-David Beyer
    Jean-David Beyer Member Posts: 2,665
    Are you surprised if one did?

    Not really. One inspector approved my new heating system when there was a 12 foot (or so) long piece of bright yellow CSST gas pipe going straight across the garage (where my heating system is) that was neither bonded nor grounded. A different inspector approved the condensate drain just dumping the condensate on the ground outside. Another inspector ... . The list never ends.
  • Timco
    Timco Member Posts: 3,025
    Leon82 said:

    It's like they saw a diagram of the concentric vent and moved it to there.



    That couldn't have run more than a few seconds before it started convulsing

    And it did not...We do allow for room air intake and there are provisions in our manuals for that, and tables showing required openings to rooms that do not provide enough free air or space. Clearly they saw a concentric and said I can do that! Same pipe is easy!
    Just a guy running some pipes.
  • Nutjob
    Nutjob Member Posts: 1
    ChrisJ said:
    In vehicle exhaust systems this would be scavenging - moving exhaust flow from a small diameter pipe to a larger diameter. But what do I know? I'm not a plumber.

  • CapnCurt
    CapnCurt Member Posts: 1
    Room air is often permitted with the appropriate room volume etc. But if the fundamental principle of a condensing boiler is to capture heat from flue gas condensate, it seems to me that the colder the intake air, the more efficient the condensate heat recovery would be... particularly if using a concentric flue arrangement. Thoughts?
  • Youngplumber
    Youngplumber Member Posts: 500
    It's more effeciant to use outside air. The air comes from somewhere, if your dragging more cold air into the house, from the windows and doors, passed the thermostat, just to heat the house, only to pull more outside air through the house, I don't see how the two can be the same. But what do I know I'm a plumber. 

    I'm not sure about it helping condensing heat recovery. 

    I do agree that there are a lot of call backs on plugged screens though. 
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