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how far is too far to exhaust a boiler?

Live/Learn Member Posts: 97
Hi Wallies! I'm a trustee of my local church and we had a puff back this past weekend. The inside of the boiler was completely plugged and full of black goop. We cleaned it very well in feb of '06 as I was involved with the cleaning. We soot sawed it and bushed it down after breaking down the whole unit. The chimney is on the outside and about 40' away from the boiler. Also the chimney is an old very large brick affair. The stove pipe runs from the boiler to the outside chimney through a crawl space. Due to this set up I believe that the exhaust gases never get a chance to really heat up enought to burn off the moisture in the system. There is condensation stains on the stove pipe. What's my sollution? Would it help to run a stainless steel directly from the boiler and up the old chimney with a cap on top? Thanks in advance for you help. Live/Learn


  • tim smith
    tim smith Member Posts: 2,738
    Regarding chimney flue

    I think you need to change your venting arrangement. Probably an all fuel insulated flue pipe to get to shortest route to outside wall and maybe a power venter. Exhausto prefferably. The venter fan and size of flue pipe can be calculated by the Exhausto rep for your size and type of boiler. I think your horizontal to vertical ratio are way out of whack for gravity venting. My .03 cents worth. Tim
  • J. Madden
    J. Madden Member Posts: 2
    distance to vent

    Oil Code is specific that if the horizontal is longer than 10' a "booster" is required. Gas Code states that the L dimension (horizontal offset) is directly related to the H dimension. Complete charts in NFPA 54 National Fuel Gas Code.
    It is NEVER a suitable situation to run single wall metal vent connector through a cold space. As a minimum Type L vent connector pipe with a booster would help, but no guarantees it will solve problem. Best to move boiler, move chimney, or sidewall vent keeping flue pipe connector in warm area.
  • Live/Learn
    Live/Learn Member Posts: 97
    boiler venting problem

    Thanks for the info on the proper specs for venting the boiler. It sure makes sense to me. I'll pass this along to the installer. Moving the boiler was already discussed as this would solve our problem. This has been giving us puff backs at least two other times. We are in the process of replacing the old WM boiler with a new Burnham anyway so now is the time to do it right. Thanks Live/learn
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