Another bathroom redo question.It’s about exhaust fans!

Discussion in 'HVAC Heating & Cooling' started by NoviceLurker, Feb 27, 2021.

  1. NoviceLurker

    NoviceLurker Member

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    The joists for the bathroom run horizontal to where I can exit the duct to a window in an adjacent room where the clothes dryer vents. There are furring strips that run 90 degrees to the joists so Sheetrock can be hung below piping. I have about 2.5” from the cross beams to the bottom of the furring strips. I would have to pinch the flexible duct to get it under the joists. Is this something I can do? If not, what, if anything, can I do to vent the bathroom? It had a vent I in there. It was 3”. I should have taken a photo of how it was run. I’m assuming it was pinched under the joists as described above.
     
  2. jadnashua

    jadnashua Retired Defense Industry Engineer xxx

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    There are some that can go through the wall versus in the ceiling, if that might work for you.

    Flexible duct has a lot of resistance to air flow. You might be able to find some thin, flat solid duct and a conversion from round to that flat.

    Size wise, it’s good to have one that can exchange 8-10 x the volume of the room per hour.
     
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  4. NoviceLurker

    NoviceLurker Member

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    I just measured. It’s 2.5” under the joists. Wall installation is not an option as the walls are 2x3 studs, and the only possible walls it could go into are the shower wall and wall above the toilet that will have a hanging cabinet. Bathroom is small. It’s about 60sf.
     
  5. wwhitney

    wwhitney Well-Known Member

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    For normal HVAC, there are duct sizes available meant for walls (google wall duct), e.g. 3.25" x 10" or 2.25" x 12". There are also oval versions; not sure if they would be less likely to collect lint.

    So it seems like you could convert from 4" round to one of those sizes, to either put the duct in the wall, or in your 2.5" clear space below the joists. Tracking down a source for the correct parts may be a bit of work. And again I'm not sure about the lint issue, if using a narrow duct is problematic (certainly no screws for assembly, just tape). You might want to include provisions for access and cleaning.

    Cheers, Wayne
     
  6. NoviceLurker

    NoviceLurker Member

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    I’ll have clear access to it. Total run will be a max of 15ft, or 10ft, depending where I locate it in the ceiling, but it will be exposed once it leaves the bathroom for cleaning.
     
  7. fitter30

    fitter30 Well-Known Member

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    Side wall mounted exhaust?
     
  8. NoviceLurker

    NoviceLurker Member

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    Can’t. See a few posts above.
     
  9. NoviceLurker

    NoviceLurker Member

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    Still thinking about this. I can put it in the wall in the back left of the attached picture. Right above the toilet and where I was going to put a cabinet since there’s no storage in the bathroom except under the small vanity that is going in there. The concern with putting it there is that would be around the corner of the wall for the shower and wouldn’t that be pretty useless? If I didn’t build a wall and just built a short curb and used a 90degree shower curtain, which is how it was with the tub, I think it would work?
     

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  10. wwhitney

    wwhitney Well-Known Member

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    Slightly confused by your comments and picture: if you have a way to get the exhaust duct from just above the toilet to the exterior, then given the direction the joists run, it seems like you would be able to extend the duct through the joists to reach the shower area.

    Cheers, Wayne
     
  11. NoviceLurker

    NoviceLurker Member

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    Put the exhaust right in the ceiling in the shower? The vent was between right wall and tub prior and the 3" flexible pipe went right over the shower into the basement then right into other bathroom.
     

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    Last edited: Mar 5, 2021
  12. wwhitney

    wwhitney Well-Known Member

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    People do that, it certainly captures the moisture, not sure if it would make an unpleasant draft. Or right at the edge of the shower, maybe.

    If you read the instructions for a bath vent, they typically say they may be installed over a shower if they are GFCI protected.

    Cheers, Wayne
     
  13. NoviceLurker

    NoviceLurker Member

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    Draft wouldn't be an issue. My concern with that was I don't know if my breakers are GFCI protected. I will look later. Will it just say it on it? If I don't have one, how difficult is it to switch it out?
     
  14. wwhitney

    wwhitney Well-Known Member

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    Doesn't have to be a GFCI breaker, it could be the GFCI receptacle by the sink, with the fan wired on the load side so it's protected.

    [There's two rules for circuiting sink receptacles: one allows a single circuit to serve the receptacle and anything else in the bathroom, but nothing outside the bathroom; that would work for protecting the fan. The other allows a single circuit to serve GFCI sink receptacles in multiple bathrooms, but nothing else can be on the circuit; if that's how yours are wired, you couldn't put the fan on that circuit.]

    As to the breaker, if it's a GFCI breaker, it will have test and rest buttons. But so will AFCI breakers. Most likely you'd need to check the literature from the manufacturer of your panel to learn how to distinguish between the two types . (Often three types, as there are also dual function GFCI/AFCI breakers). Sometimes one of the parts is color coded.

    Cheers, Wayne
     
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