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Thread: Exhaust fans shuttered- for finish room exhaust

  1. #1
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    Exhaust fans shuttered- for finish room exhaust

    Looking to hook up a shuttered exhaust fan into my 9x11' finish room. No sheet rock or siding up yet, that's next week, so need to make a decision quick.
    2 questions-
    1. What fan do you guys like, don't like? I see Homers has a few, but no idea if they're any good. Some reviews said the shutters don't completely close. Was going to install it from inside, but I need to make a decision on whch on, or is there a good supplier that has quality ones? If so, please enlighten me.
    2. What size do I need for a 1 man finish room 9x11'? I'd sure like t stay as small as possible both for aesthetics, but also to minimize my exposure to the elements as much as possible. HD has a 10", that it says puts out 600cfm. Amazon has a 7" at 242 cfm. Is that sufficient for this? Sure sounds like it should be, but I have no idea on that. ?
    3. What else should I know or think about? will have a filtered inlet on other side of wall. Was going toput inlet down low, and exhaust up hgh on opposite wall. Ideas?

    Thanks so much!!

  2. #2
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    I'm working on the same thing for my shop too.

    I have a 20" x 20" explosion proof fan. Canarm is the brand.

    If you have any desire to spray lacquer or any other possibly explosive finishes, having an explosion proof fan is a must. If you'll be spraying water based finishes, not an issue.

    I'm getting electrically activated louvers. I agree you need something to prevent the elements from coming in.

    Mine is 3640cfm, so a whole different beast.
    Last edited by Alan Lightstone; 08-07-2019 at 9:11 AM.
    - After I ask a stranger if I can pet their dog and they say yes, I like to respond, "I'll keep that in mind" and walk off
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  3. #3
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    We worked on a spray room for a cabinet shop that had 4 spray booths and a drying conveyor. They had it engineered to change the air in the room once every 30 seconds. While in operation, you could definitely smell the lacquer, but it wasn't intense. I would use that as a target when designing the exhaust system. Assuming you have an 8' ceiling, the room volume would be 792 sq. ft. So to provide 2 air changes per minute, a 1600 CFM fan is needed. And of course, you need to have provision for make up air to suit.

    That 242 CFM fan would take so long to clear the fumes that there would be a real danger of developing an explosive atmosphere while spraying.

  4. #4
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    consider multiple fans, one for exhaust and one for makeup. Then a couple small ones inside to keep the air moving uniformly.
    Size the makeup a little larger than the exhaust to make the room positive pressured.

    My dad did auto body work and was a firm believer in a positive pressure environment to keep the dirt and dust at bay.

    Edit: I see you have a thread with that topic. Mods, feel free to move this if you see fit.
    Last edited by Charlie Velasquez; 08-07-2019 at 3:04 PM.
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  5. #5
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    Thanks so much for the input!!

    Alan, Frank & Charlie, thank you so much for the input, that's really helpful!!
    The sizing idea of the two fans is what I needed to hear Charlie, excellent! )

  6. #6
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    As others have mentioned if you spray flammable materials you’re going to need an explosion proof fan as well as all the electrical devices in the room.

    I also suggest you talk to the local building code authority and your insurance company......Regards, Rod.

  7. #7
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    Quote Originally Posted by Rod Sheridan View Post
    As others have mentioned if you spray flammable materials you’re going to need an explosion proof fan as well as all the electrical devices in the room.

    I also suggest you talk to the local building code authority and your insurance company......Regards, Rod.
    Ditto. You just can't be too careful about spraying flammable materials. Or putting out rags that spontaneously combust, for that matter, but I digress.
    - After I ask a stranger if I can pet their dog and they say yes, I like to respond, "I'll keep that in mind" and walk off
    - It's above my pay grade. Mongo only pawn in game of life.

  8. #8
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    I got my variable speed, explosion proof fan from Autobody Toolmart. It is a Jenny. IIRC, on high speed it pulls over 10,000 cfm but they have smaller models.

  9. #9
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    Ooooh!!!! Variable speed would have been nice. Mine is single speed, although, I guess, I could modify that electrically.
    - After I ask a stranger if I can pet their dog and they say yes, I like to respond, "I'll keep that in mind" and walk off
    - It's above my pay grade. Mongo only pawn in game of life.

  10. #10
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    return filtered air

    Quote Originally Posted by Alan Lightstone View Post
    Ooooh!!!! Variable speed would have been nice. Mine is single speed, although, I guess, I could modify that electrically.
    Alan et al,
    how did you setup the filtered air for return air? Whay size fan did youi get and from where if you remember?I assume attached thru some sort of plenum, but not being an AC guy, I have very little knowledge in that regard, so any help is much appreciated! Pictures would be awesome if possible! TIA!!
    Dave

  11. #11
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    A simple fan motor with no capacitors can be made variable speed very easily. A simple SCR speed control will do that. Unfortunately it reduces max speed to about 1/2 of full speed. But then it is variable below that.
    Bill D.

  12. #12
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    In my case, the only way I could get sufficient return air was by opening a window and making a filter box for the window. Making everything soundproof made it also very air tight.

    I made a 20x20 box, and use the same filters and use for the same filters that I use for the fan.

  13. #13
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    Quote Originally Posted by Bill Dufour View Post
    A simple fan motor with no capacitors can be made variable speed very easily. A simple SCR speed control will do that. Unfortunately it reduces max speed to about 1/2 of full speed. But then it is variable below that.
    Bill D.
    What is a SCR speed control?

  14. #14
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    Quote Originally Posted by Alan Lightstone View Post
    In my case, the only way I could get sufficient return air was by opening a window and making a filter box for the window. Making everything soundproof made it also very air tight.

    I made a 20x20 box, and use the same filters and use for the same filters that I use for the fan.

    OH, ok, TY. You must have two windows in finish room then, one for exhaust, and one for intake? Or do you use a louvered exhaust fan for outside?

  15. #15
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    A shutter on the outside that swings up may be the best way to keep the weather out. If it's twice as wide as the opening and only swings up about 45 it should be good. Insulate it. You could make it operable from the inside. Make it a little taller and hinge it a few inches above the opening.

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