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Thread: Vent clearance

  1. #1
    mathew stouffer's Avatar
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    Default Vent clearance

    This appeared to be single wall vent or Z vent, although there was no information tag. The boiler is gas, 300 BTU. The Vent is 5 inches from the drop ceiling. Looks like 1in unenclosed, although wanted to get some input on type of vent. Thx

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  2. #2
    David Bell's Avatar
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    Default Re: Vent clearance

    Looks like PIC vent which is a pressurized industrial chimney system.

    Last edited by David Bell; 01-18-2011 at 09:02 AM.

  3. #3
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    Default Re: Vent clearance

    Quote Originally Posted by mathew stouffer View Post
    This appeared to be single wall vent or Z vent, although there was no information tag. The boiler is gas, 300 BTU. The Vent is 5 inches from the drop ceiling. Looks like 1in unenclosed, although wanted to get some input on type of vent. Thx
    I suspect you meant 300 Mbtu.

    Depends on the mfg. Distance for the run must meet both the boiler mfg instructions/limitations as well as the Special Gas Vent manufacturer's instructions/limitations.

    There is no proper elbow or horizontal run support shown. That miscellaneous wire or cable at the second elbow and connected to the non-structural ceiling tile grid is NOT correct support. Guy bands and 500 lb wire cable or metal straps (loose fitting and still permitting movement/expansion/contraction overall, at joints, changes in direction, etc.) yet still properly supported from structure, and preventing collision or rather maintaining operating clearances and required air space.

    Unknown if proper thimble at wall, not pictured.

    Unknown if proper support colar at base (boiler flue) is present, not pictured.

    Do not see condensate drain or T for same, appears downward slope after second elbow in 2nd pic.

    Does appear to be double wall z-vent. Above 4"+ clearance to non-heat sink/stopped combustible ceilings, structure and underside of roof decks is a common specification on horizontal runs.

    IIRC UL Standard is 1738 for Special Stainless Steel Venting System for Gas Burning Appliances. Boiler mfg instructions likely refer to NFPA 54 or its ANSI designation. Mfg instructions for both the boiler (appliance) and the special gas venting must be followed, as must local codes when more restrictive.

    Clearances and instructions may vary depending on output flue temperature.

    IIRC you are in a high altitude zone.

    Support lacking. See no provisions for condensate drainage. Too many unknowns and without scale to determine much else.

    Is this a residential, multi-family residential, commercial, mixed use, or industrial installation?

    What is in the background of pic 2 - is that gas piping and an enclosed regulator?


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    Default Re: Vent clearance

    P.S. The horizontal path also seems to go under a diffuser panel installed in the non-structural drop ceiling, likely representing installation above of a heat producing, etc. fluorescent ballast, lamp tubes, light(&heat) reflector, etc. accessibility for the lamp tube changeout, (presume hinged diffuser panel, but perhaps not) maintenance, etc. (dedicated equipment space) as well as proximity for heat on low-temp double wall is likewise compromised - protection from damage of the special venting system is likely compromised by the presence of this diffuser panel and luminaire.




  5. #5
    David Bell's Avatar
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    Default Re: Vent clearance

    If it is PIC vent a 4" clearance is required. IPIC can be as little as 1"


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    Cool Re: Vent clearance

    The rating plate on the appliance will state the venting Category and clearances to combustibles when using the pipe specified. Some will allow any brand of venting appropriate to that class while others may specify just one vent, such as their own pipe.

    Good points by HG. Some mfrs. require a condensate trap in the venting while others want it to drain back to the appliance. That drop ceiling grid does not provide adequate support for the vent.

    Shifting gears, I don't see the required upstream shutoff and sediment trap or downstream trap on that MP regulator. I see the vent is extended through the wall.

    Did you calculate the MUA requirements?
    HTH,

    Keep the fire in the fireplace.

  7. #7
    mathew stouffer's Avatar
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    Default Re: Vent clearance

    I meant 300,000 btu's. There are two boilers sitting on top of one another. There is a condensate trap below the vent at the junction of the two vents. No I did not cal the MUA. I'm assuming you mean make up air, which would involve adding up the BTU's of the three boilers ( two 300,000 btu and one 1.2million btu boiler) and measuring the square footage or the room and combustion air vents, to start

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  8. #8
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    Default Re: Vent clearance

    Thanks for quickly responding to the hail and posting Bob Harper!

    I thought I was seeing a MP (medium pressure) regulator and a relief or breather vent through the wall behind it (hopefully to outdoors), but I too did not see a shut off or trap.

    I was equally curious why the boiler exhaust vent didn't exit through the same wall - different location, if it (the wall) is an exterior one.


  9. #9
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    Default Re: Vent clearance

    Quote Originally Posted by mathew stouffer View Post
    I meant 300,000 btu's. There are two boilers sitting on top of one another. There is a condensate trap below the vent at the junction of the two vents. No I did not cal the MUA. I'm assuming you mean make up air, which would involve adding up the BTU's of the three boilers ( two 300,000 btu and one 1.2million btu boiler) and measuring the square footage or the room and combustion air vents, to start

    Whoa.

    Mat,

    Here's an article that I believe you will find isn't overwhelming, is well written and may help you address and identify, this is a direct clickagle link: Back to Basics: Venting for Gas-Fired Boilers - Feature Articles - PMEngineer

    It is from the Back to Basics Column from PMEngineer. It is specifically on-topic as your topic has developed.

    I hope you find it helpful/useful.

    Sincerely,

    H.G.


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