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combi venting through floor

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maxsoda
maxsoda Member Posts: 4
I'm installing a combi boiler in a 7' crawl space. I want to vent the the combi vertical through the above plywood (osb) floor, into the above main floor stairs closet, and then 90 to the outside. I can not find anything concerning venting though a floor and then outside (everything is through the floor and through the roof). What is the code concerns when venting through the floor. The combi 3" pvc exhaust temp will be below 144 fahrenheit.

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  • mikeg2015
    mikeg2015 Member Posts: 1,194
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    Crawlspace will need ot be sealed and insulated. You can’t install condensing appliances where it could freeze.

    No sure on code. Should only matter the total equialvanent lenght of pipe. But again, if the crawlspace is cold, you can invite issues as the exhaust temps get too cold and invite freezing at the exhaust.

    Also a damp crawlspace will destroy these units fast. Condensation inside the cabinet.


    I strongly recommend you find a closet near an outside wall for it if possible. Easier ot run longer header than vent pipe. Keep the unit in conditioned space.
  • SuperTech
    SuperTech Member Posts: 2,188
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    Keep the unit in a clean, conditioned space that an adult can easily fit in and still be able to access every component of the boiler.
    The boiler shouldn't be kept hidden and out of sight. It should be proudly kept on display, unlike a stove or refrigerator this appliance keeps you and your family warm and alive when the cold outside is life threatening!
    Treat your boiler like you would a sports car. Don't buy the least expensive option, keep it clean and serviced. Take pride in your heating equipment, it's not cheap to operate!
    kcoppAdolfo2Solid_Fuel_Man
  • bob eck
    bob eck Member Posts: 930
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    Why can’t you put the boiler in the closet on the first floor?
    Bring in fresh air from outside the house.
    Most condensing combi boilers are very quiet and it would be very easy to work on.
    kcoppSuperTech
  • Ironman
    Ironman Member Posts: 7,379
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    I agree with the previous comments that you'd be much better off putting the boiler in the closet and not the crawl space.

    As far as the vent pipe goes: it can penetrate the floor as long as it's properly fire stopped and protected from physical damage.
    Bob Boan
    You can choose to do what you want, but you cannot choose the consequences.
  • gennady
    gennady Member Posts: 839
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    You can vent category 4 through house, but it must be enclosed into fire rated enclosure (2 layers if 3/8 sheetrock), with fire rated access panels for routine inspections, also, i would install CO detectors at each floor, interlocked with boiler, so, in case of CO presence they would shut down boiler. It must be filed by architect with dob.
  • maxsoda
    maxsoda Member Posts: 4
    edited February 2019
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    Thank you for the response. The crawls space is basically a basement (cement floor, ICF walls, insulated, will be heated). The main floor does not have room for all the radiant plumbing equip. The house is in the mtns at about 10,200 ft. Snow is a big issue. That is why i want to run the vent through the floor and out.
  • SuperTech
    SuperTech Member Posts: 2,188
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    Plumbing and can go in the crawl space, the boiler should be above, ideally.
  • DZoro
    DZoro Member Posts: 1,048
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    You mentioned 7' crawl space, does that mean it's 7' tall?
  • maxsoda
    maxsoda Member Posts: 4
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    Crawl space is 7' tall.
  • DZoro
    DZoro Member Posts: 1,048
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    That should be fine, insulate the pipes if going into a cold area. Size and slope per O/M.
    D
  • Solid_Fuel_Man
    Solid_Fuel_Man Member Posts: 2,646
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    Why do you call it a crawl space? Sounds like a basement to me. Lots of basements are less than 7' around here.
    Serving Northern Maine HVAC & Controls. I burn wood, it smells good!