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Required distance between bathroom exhaust and furnace intake or exhaust

Jase
Jase Member Posts: 2
in Gas Heating
Is there a minimum distance that a bathroom fan exhaust vent on the outside of a house must be from a high efficiency furnace intake or exhaust?

Thanks

Comments

  • hot_rod
    hot_rod Member Posts: 23,400
    It should be in the installation manual. I’d use the installation directions from the brand and model you have, or have in mind. It could vary from brand to brand. They will show a bvertical and horizontal dimension

    If at all possible I would go up with flue and intake. Those intakes are basically vacuum cleaner
    Bob "hot rod" Rohr
    trainer for Caleffi NA
    Living the hydronic dream
  • EdTheHeaterMan
    EdTheHeaterMan Member Posts: 9,400
    The idea is to keep exhaust gasses from entering a building and recirculation of exhaust gasses in the combustion air. So the bathroom exhaust vent opening is not really a problem. If it were a fresh air intake, then there would be a cause for concern. Putting a furnace exhaust within a foot or two of a bath exhaust is not going to cause any operational problems for either device.

    The air intake of a furnace should not be close to an exhaust that contains byproducts of combustion. This will reduce the amount of oxygen available for combustion. A bathroom exhaust fan does no have byproducts of combustion, Just some humid air and the occasional unpleasant odor. No need for concern there either.

    All the venting diagrams will show windows, doors and fresh air intake openings. Never saw a minimum dimension from an exhaust opening.

    Edward Young Retired

    After you make that expensive repair and you still have the same problem, What will you check next?

  • pecmsg
    pecmsg Member Posts: 5,297
    EdTheHeaterMan said:
    The idea is to keep exhaust gasses from entering a building and recirculation of exhaust gasses in the combustion air. So the bathroom exhaust vent opening is not really a problem. If it were a fresh air intake, then there would be a cause for concern. Putting a furnace exhaust within a foot or two of a bath exhaust is not going to cause any operational problems for either device. The air intake of a furnace should not be close to an exhaust that contains byproducts of combustion. This will reduce the amount of oxygen available for combustion. A bathroom exhaust fan does no have byproducts of combustion, Just some humid air and the occasional unpleasant odor. No need for concern there either. All the venting diagrams will show windows, doors and fresh air intake openings. Never saw a minimum dimension from an exhaust opening.
    I don’t know. How good is that back flow damper?  I’d still consider it an opening ( window, door) and treat it as such 
  • pedmec
    pedmec Member Posts: 1,066
    think of it in reverse. not worrying about the exhaust air from the bathroom entering the intake air for the boiler but the flue gases entering the exhaust fan from the boiler when the exhaust fan is not being used. everybody know that the dampers on the exhaust hoods are terrible. they are not 100% sealed when functioning nor do they last. most dampers are stuck open or broke. if your house is in a negative from from say the dryer running, water heater is operating, etc. you could be in a slight negative in the house and any exhaust gases can enter due to the pressure.

    its most likely a crazy scenario but one that only needs to happen once. so the father the better.
    pecmsgDave CarpentierIn_New_England
  • Jase
    Jase Member Posts: 2
    Thanks everyone for your replies. The installation manual does not mention bathroom vents in the clearances section. I have not been able to find any minimum distances for bathroom vents from furnace intakes/exhausts in any codes or manuals. Unfortunately, it seems like there are no codes or manufacturer recommendations on this subject, but placing it too close does seem like a bad idea.
  • hot_rod
    hot_rod Member Posts: 23,400
    As pedmec mentioned, the potential for exhaust to enter into the vent would be my concern, especially if you get wind against the building. Why risk it if you have options?
    Bob "hot rod" Rohr
    trainer for Caleffi NA
    Living the hydronic dream
  • Alan (California Radiant) Forbes
    Alan (California Radiant) Forbes Member Posts: 4,214
    edited June 2022
    If you are considering that an exhaust outlet could become an inlet, follow the manufacturer's instructions for proximity to inlets.

    Lochinvar instructs the following for their Knight boilers:






    8.33 lbs./gal. x 60 min./hr. x 20°ΔT = 10,000 BTU's/hour

    Two btu per sq ft for degree difference for a slab
  • pecmsg
    pecmsg Member Posts: 5,297
    Jase said:

    Thanks everyone for your replies. The installation manual does not mention bathroom vents in the clearances section. I have not been able to find any minimum distances for bathroom vents from furnace intakes/exhausts in any codes or manuals. Unfortunately, it seems like there are no codes or manufacturer recommendations on this subject, but placing it too close does seem like a bad idea.

    Treat the vent as an opening!
    GGross

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