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Direct Vent distance between inlet and vent

cgw Member Posts: 42
A developer has had probelms with snow blocking inlets of direct vented furnaces. For a new building he wants to put the vents on the roof and the inlets on the wall. The furnace instuctions say in the "same pressure zone".  Can this be done?

The building has four floors so the lowest furnace inlet will be be a little more than 3 floors below the vent on the roof.


  • Tim McElwain
    Tim McElwain Member Posts: 4,506
    It is hard to say

    if it can be done or not. In many cases if the manufacturer states a distance that intake  air and exhaust must be then you must follow that. I would get a ruling from the equipment manufacturer, probably a good idea to get the answer in writing from them.
  • Big Ed_4
    Big Ed_4 Member Posts: 1,884
    I Agree

    They may tell you to install both on the roof where it will be in the same pressure zone .They may also tell you increase the vent size over a certain length .. just a good guess . To have the intake and vent in the same pressure zone both would have to be on the same wall or roof of the building ... But I agree if it's not printed one way or the other , call the manufacture for the green light ...
    I have enough experience to know , that I dont know it all
  • Jack
    Jack Member Posts: 1,046
    An alternative is...

    to suggest other side wall locations. such as an exterior wall closet and then box the piping in. As well, I've had guys run some of our DV equipment vents up behind the lazy susan in the kitchen. That is the deadest of dead space and gains quite a lot of height above grade. To paint PVC I've always wiped it with hite vinegar to strip it and then painted it out to match.
  • Henry
    Henry Member Posts: 995
    Direct vent instructions

    In Canada, you have no choice but to follow to the letter the manufacturer's certified instruction manual. That means in your case, both pipes must be in the same area! A phone call will not legaly permit you to do otherwise. An email from the manufacturer might be acceptable to Authority Having Jurisdiction. I beleive that NFPA 54 is similar.

  • Tim McElwain
    Tim McElwain Member Posts: 4,506
    In court cases I have

    been involved with as an expert witness it must be a formal letter from the manufacturer specifying the exact alteration that can be made. Nothing else is acceptable. It is a called a proper chain of evidence to support an action or behavior.
  • cgw
    cgw Member Posts: 42
    Furnace instructions

    A boiler installation instruction kind of addresses the distance between the intake and vent but a Furnace installations instruction does not mention it (Carrier). The gas code (NY State) does not address it as far as I can see.
  • Tim McElwain
    Tim McElwain Member Posts: 4,506
    Get a hold of the manufacturer

    they are the only ones who can answer your question or give you a ruling. Local codes do not normally address venting of high efficiency equipment as it is per manufacturers instructions and nothing else.
This discussion has been closed.