Booth Filter Consideration

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PostPosted: Mon Oct 01, 2018 3:52 pm
So doing a little planning on booth build. Initial thoughts are positive pressure booth, fans on one end, partial opened overhead garage door on the other. So building a bank of filters for fan side. Wondering a couple things. How to determine how many intake filters are needed. Planning to use 20x20 series 55 filters. Do we take into consideration how much cfm the filter kills when you put it in front of a fan? Maybe I'm being over critical. Say, two, 4000 cfm fans...if I put 4 filters in front of them, vs 8 filters in front of them, the results will for sure be diff. Also, call this a cross draft if you will, is better to mount the fans/intake filters higher up, or floor level. I found 68 Coronet R/T post about his booth, long ago, but now the pictures won't show for me. I'd probably be something similar to that. thx in advance.



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PostPosted: Mon Oct 01, 2018 6:01 pm
Thinking about it more now... I'd assume mounting intake filters higher, as to send flow across the room at an angle, picking up over spray from mid air and sending it down towards the exit at the garage door opening. Anyone confirm this theory?

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PostPosted: Mon Oct 01, 2018 9:42 pm
If you do not have exhaust side fans to pull the air out while the intake fans are pushing it in then you will have turbulence. This will be compounded by a smaller filter bank as the faster moving air will cause curl back along the walls of the booth.

Downdraft booths where the air flows from the ceiling to the floor or outside wall exhaust ducts create an area where there is no turbulence or chance of over spray circling back onto your paint job.

Crossflow booths follow basically the same principle by creating a channel of air moving through the booth.

Those of us just trying to get a clean environment to paint our hobbies in, generally construct positive flow booths that are not true crossflow booths because they only have filtered intake air and no exhaust filters or fans. We rely on the intake fans to push the air through the booth and out the other end.

My experience with this has taught me that a larger filter bank helps reduce turbulence my moving a larger "wall" of air through the booth. Getting the garage door set to the right sized opening is a bit of a challenge since you have openings at the top and bottom when you raise the door. The ideal amount is when you have positive pressure in the booth but not so much that the air is bouncing back from the garage door and swirling in the booth.

When adjusted right the cloud of over spray from the clear coat can be seen visibly exiting the booth.
1968 Coronet R/T


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PostPosted: Wed Oct 03, 2018 8:40 am
Thanks for the details Coronet. I'm thinking about an exhaust plenum, that will be 2 filters tall by 4 or 5 wide, as wide as the overhead door, that you can lower the door onto. Then do my best to build an insert that will cover the gap left at the top of the door from being partially opened. I can tape all the seams to seal it best I can, that's what I normally do now and it works pretty decent. Planning an exhaust fan, with same or slightly less cfm than the intake, and mounting the motor on the outside of the fan area to keep it separate from the fumes of course. Same or more cfm from the exhaust would be good, then I could adjust it with a damper of some sort. Perhaps a fan speed controller would work as well.
Right now, I have one wall, that is the shop wall, then the garage door, so that's another wall, so I'm just trying to nail down plans for a temp wall on the other side. I want to be able to break it down so when I'm not doing painting, I can use my shop normally.
One option is plastic, fastened very securely on top, and bottom, but plastic always seems to give me problems. Seems like it's always tearing or coming loose when you pressurize the booth. I'm also considering 4 or 5' wide framed sections, that I can line up and secure as temp walls. Making them only 4 or 5' wide so I can disassemble and lay against a wall when not being used. Also, try to keep them light, so they aren't too heavy to handle setting up and taking down.
Right now, I'm doing some design and layout in a CAD program, I'll post a couple pics of the models when I get it a little closer to being able to look like it's something.
If I had the room, I'd buy a booth, but I don't have that large of a shop, 30x40, and I don't paint often enough to justify the spend. What I'm doing will be better than spraying without any airflow or ventilation, and for sure be better than spraying outside. Main things are that I get the fumes out so it's better for me, and that I don't get junk in the paint while I'm spraying.



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PostPosted: Sun Nov 25, 2018 11:11 am
For all the hassle of trial and error and the expense of trying to build a Paint booth you can buy a decent used one cheap that includes the fan and lights.

This is Nicer than mine as its a true Down draft. You'd have to do some digging and cement work but this is a great booth for the money.
https://sandiego.craigslist.org/esd/hvo ... 11877.html

Here's A semi down draft similar to mine for $4500 Includes an attached mixing room and if you can get him to throw in that Devilbiss Air filter system, I bet he would. Then that would be a super Killer deal that's a $1000 bucks right there! Not to mention it includes A fire sprinkler system that's a Major bonus as well.
https://losangeles.craigslist.org/sfv/p ... 10078.html
Dennis B.
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