Exhaust fans shuttered- for finish room exhaust

[Dave Burson]

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!!

[Alan Lightstone]

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.

[Frank Pratt]

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.

[Charlie Velasquez]

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.

[Dave Burson]

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! :))

[Rod Sheridan]

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.

[Alan Lightstone]

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.

[Allan Dozier]

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.

[Alan Lightstone]

Ooooh!!!! Variable speed would have been nice. Mine is single speed, although, I guess, I could modify that electrically.

[Dave Burson]

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

[Bill Dufour]

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.

[Alan Lightstone]

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.

[Alan Lightstone]

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?

[Dave Burson]

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?

[Tom Bender]

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.

[Tom Bender]

One challenge when designing an automobile paint booth is airborne mist of sprayed finish settling on the fresh paint. Great effort and expense is lavished on this issue. Commonly the air is kept as still as possible and filtered air is pulled in thru the ceiling and contaminated air is pulled thru the floor.

In your case you will be pulling from a wall. Ideally you will make opposite walls out of filters for 72 square feet each. Beyond one wall will be a wall of fans, say 72 of them. They will pull air thru the intake filter wall, thru the booth at very low velocity and thru the exhaust filter wall.

Well obviously you will not build an ideal booth but it helps to understand the mist issue.

[Leo Graywacz]

I got my shutters from Grainger.com. I have a 36x36 shutter I believe. I have a 3HP 36" Tubeaxial fan for my exhaust. The shutter I picked has felt on the ends of each shutter so it closes softly and seals better than one without. But don't expect a tight seal. They operate by airflow and gravity. When the wind is whipping up you can hear them open and close because of the pressure differences created from inside and outside the booth For the most part they work well.

[Ole Anderson]

I just replaced a 16" kitchen exhaust fan at church with this shuttered fan from Northern Tool. Max 2300 cfm, Canarm brand, 3 speed, good shutters, reasonable price, not explosion proof.
https://www.northerntool.com/shop/tools/product_200631892_200631892
https://www.northerntool.com/images/product/65x65/447/44779_65x65.jpg

[Dan Coker]

I will add my .02 cents. I built a separate dedicated 8ft x 8ft x 10ft spray booth that I use to spray my finishes. I also have a 16ft x 20ft+ paint room that basically functions as a drying room to keep air born particulate and such from the main part of the shop from getting into the finish. This has worked very well for me. I use several 1,200cfm exhaust fans vented through the wall outside. I have never been too concerned with the make up air nor do I know how to optimally design the make up air system. My shop is huge and I never spray more than a couple hours at a time. I have never felt the effects of loosing my cooled or heated air. This setup has severed me well. My fans are explosion proof too. One day I will setup a real system done correctly.

If you are on a budget, Harbor Freight makes a common cloned model tube exhaust fan just like I use that is cheap as heck at like $75 and it moves over 1,000cfm.

[Alan Lightstone]

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?
No, actually one window, and the 20'x20' hole we cut in the cinder block and installed the fan and louver assembly in. Had electric louvers, but they failed almost instantly, and took out the motor and let them open manually.

I've spent all weekend making a filter holder for the fan, and now will be making a overhead Plexiglas plate for over the spray table, and completing the booth.

Should be able to spray soon.

I also had to build a filter holder for the window for incoming air. So, all-in-all, a tremendous amount of work, but I should have a working finishing room, hopefully by the end of the week if I can source large enough plexi/lexan.

[William Hodge]

It's worth reading the code for spray booths to catch some other stuff, before you do it.

I built a spray booth for the shop I was working in. The lights needed to be explosion proof, so that you would,'t be in the dark of something popped. All the conduit in the spray area needed to be threaded and sealed. There was a bunch of other stuff, too. Most of it was common sense, but it doesn't hurt to be reminded.