Building a paint booth - couple of questions

Hi, Rich.

Rich.Carpenter wrote:

I've read through a lot of the past threads on the subject and gotten some great ideas and info, but there are a couple of questions I have that didn't seem to be addressed to any extent: 1. If I utilize a plenum to even the air flow across the filter, does it make a big difference if the exhaust fan is not centered behind it? Could it even be *way* off-center? I'm tossing around different cabinet designs, and placement of the fan will have a direct bearing on size and shape.

If you have to mount your fan way off center, I would suggest not connecting the fan directly to the plenum, but possibly using a reducer and a small amount of ducting.  At least this way, pressure and airflow are equalized.

Rich.Carpenter wrote:

2. Do those of you with enclosed cabinets utilize an intake filter in addition to an exhaust filter? I would think clean air coming in would be definite plus, but 90% of the time the air is being circulated, I'd have a wide open face area, anyway.

I've never seen an intake filter except in walk-in booths, and the highest rated biological safety cabinets.  With an open face area, an intake filter is not going to help.

Rich.Carpenter wrote:

3. I've seen mention of various amenities that are useful if designed into the cabinet. Some of the booths I've seen show the walls lined with stuff like paints, brushes, tools, cleaning supplies, etc. Do a lot of people keep this much stuff in their paint booths? It looks convenient, and if it doesn't fly against conventional wisdom, I'll need to consider building in shelves and such.

Everything you put in a booth adds turbulence, and ultimately reduces airflow velocity.  There are a lot of folks that do what you indicate.  Personally, I would advise against it; spray booths are not designed for equipment storage.

Good luck with your build.

Gip

styrene wrote:

Hi, Rich.  Rich.Carpenter wrote: I've read through a lot of the past threads on the subject and gotten some great ideas and info, but there are a couple of questions I have that didn't seem to be addressed to any extent: 1. If I utilize a plenum to even the air flow across the filter, does it make a big difference if the exhaust fan is not centered behind it? Could it even be *way* off-center? I'm tossing around different cabinet designs, and placement of the fan will have a direct bearing on size and shape. If you have to mount your fan way off center, I would suggest not connecting the fan directly to the plenum, but possibly using a reducer and a small amount of ducting.  At least this way, pressure and airflow are equalized.

Thanks, Gip. This is actually the concept I was considering for incorporating the plenum. What I'm trying to do is avoid having a big fan stuck on the back of the cabinet, as that would move the booth away from the wall nearly an additional foot. Also, I'm considering the cross-draft design to allow for me to build in the drawer for storage.The filter may well not be as tall as depicted. I would likely use a shorter filter, thereby moving the exhaust area down for a bit of a cross/bottom-draft design.

Rich,

It's always good to see a picture! (I even colored it, but now there's crayon all over my monitor... )

I like your design.  My only question/concern would be that you might lose airflow further away from the fan, but would have tons of pull closer to your fan.  You might want to consider a small baffle (?) in the plenum near the fan that would even out the airflow.  On the other hand, given the location of your fan and the "box" part of the plenum where it's mounted, airflow may actually tend to equalize across the filter area.  My final advice? Build it the way you have designed it, try some smoke (incense, blown-out candle, etc.) to see where the air is going, and then make adjustments accordingly.

Sorry, but I envisioned a hood with all your modeling tools stored inside.  Your idea of incorporating a drawer system with your hood is quite ingenious, and immensely practical.

Please keep us informed of your progress, and post pictures!

Gip

styrene wrote:

I like your design.  My only question/concern would be that you might lose airflow further away from the fan, but would have tons of pull closer to your fan.  You might want to consider a small baffle (?) in the plenum near the fan that would even out the airflow.  On the other hand, given the location of your fan and the "box" part of the plenum where it's mounted, airflow may actually tend to equalize across the filter area.  My final advice? Build it the way you have designed it, try some smoke (incense, blown-out candle, etc.) to see where the air is going, and then make adjustments accordingly.

That was my concern as well. Knowing no more than I do about airflow principles, I was curious how it would behave with this design. What I *can* be reasonably confident of is that the airflow will either be even across the filter top to bottom, or, as you said, stronger at the bottom. The latter would actually be the desirable of the two for me. It would give me sort of a "gravity boosted" cross-draft design.

styrene wrote:

Sorry, but I envisioned a hood with all your modeling tools stored inside.  Your idea of incorporating a drawer system with your hood is quite ingenious, and immensely practical.

Your impression was correct, actually. I was curious about booths I've seen with the interior walls lined with various paints and other implements. It only makes sense that it would impede airflow. I was just curious as to whether or not folks often find the convenience more than worth what little adverse effect it may have on air movement.

styrene wrote:

Please keep us informed of your progress, and post pictures!

Count on it. I'm pretty OCD when it comes to this sort of thing (basically anything that requires more than a modicum of forethought and planning). I don't mind putting extra effort into a job like this, if it helps me "make it count" and end up with something that satisfies my needs as completely as possible. I'll post more pics - perhaps some WIP stuff as well - and, if it works as well as I'm hoping, I'll provide the plans as well.

Thanks again!

Got the preliminary design fleshed out. I still have a couple of things I need to settle on, though:

• What type of lighting to go with. The "puck" lights in the drawing work well from an aesthetics standpoint and would provide excellent quality lighting, but low voltage would be a bit more of a hassle to hook up. Even if I stick with the pucks, I'll probably cut back to just two of them.
• What sort of electrical service to install. I'll probably go with a simple 2- to 6-outlet power strip, mounted on the side.
• Where and how to route my air hose(s). I'd like to mount the regulator/moisture trap on the inside side wall. I'm thinking perhaps a gasketed port in the side wall.
  
• How to best provide a plenum vent for when I may want to reduce the air moving through the booth. I've got a couple of ideas that will work. It's just a matter of settling on the one that is most functional and unobtrusive.
• I've not completely settled on mounting the filter inside the booth. I'm still toying with the idea of building in an exterior accessible slot - possibly with a latched cover - that the filter would slide into.

Anyway, that's where I am with it so far. I'm purchased the wood and plexiglass door hardware at this point. The framework will be 3/4" pine, the cabinet 1/4" birch finished plywood and the bottom 1/2" birch finished plywood.

Any ideas are welcome. :)

Finally got started today. I altered the design to incorporate some electrical amenities such as a three-toggle switch (lights, fan, compressor) and a 2-plug outlet, switched for the compressor and possibly the fan.

I've gone through 40' of 1x1 stock pretty quickly. The framing is proving to be a bit more involved than I had expected, after adding the chamber for wiring and considering sealing off the exhaust plenum chamber.

Anyway, here are some pics so far:

Rich.Carpenter wrote:

Where and how to route my air hose(s). I'd like to mount the regulator/moisture trap on the inside side wall. I'm thinking perhaps a gasketed port in the side wall.

In the "for-what-it's-worth" category, the industrial booths I have had dealings with--all the compressed air quick-releases and components were mounted on the exterior wall of the booth, adjacent to, and pointing towards the face.  Hoses were simply brought into the booth from the outside.  The purpose of course, was to prevent the escalation of a booth fire due to the failure of compressed air components inside the booth. From a purely safety standpoint, I would suggest consideration of something similar.  You could also mount your hosing and water trap from your compressor on the outside, and pass your airbrush hose through a rubber grommeted hole in the booth wall.  The rubber grommet would keep your airbrush hose from being abraded, and give the added benefit of sealing around the hose to prevent air leaks (see additional info below).

Rich.Carpenter wrote:

How to best provide a plenum vent for when I may want to reduce the air moving through the booth. I've got a couple of ideas that will work. It's just a matter of settling on the one that is most functional and unobtrusive.

Just curious, Rich--what is your rationale for wanting to reduce air movement through the booth?  If that's indeed a necessity, would it be easier to install a simple rheostat controller in place of the on/off switch?

Rich.Carpenter wrote:

I've not completely settled on mounting the filter inside the booth. I'm still toying with the idea of building in an exterior accessible slot - possibly with a latched cover - that the filter would slide into.

Great idea.  Sure makes for quick and easy change-outs.

Rich. Carpenter wrote:

Any ideas are welcome. :)

Just one additional suggestion:  Make sure the attachment points for your fan, and your plenum box are completely sealed.  Nothing destroys airflow quicker than leaks.  Consider gluing your joints, and then caulking everything.

All the best!

Gip

styrene wrote:

In the "for-what-it's-worth" category, the industrial booths I have had dealings with--all the compressed air quick-releases and components were mounted on the exterior wall of the booth, adjacent to, and pointing towards the face.  Hoses were simply brought into the booth from the outside.

Good idea. That's probably the way I'll go. After all, there really shouldn't be any need to have my AB hanging in the rack much when the door is closed, provided I'm practicing good cleaning habits.

styrene wrote:

Just curious, Rich--what is your rationale for wanting to reduce air movement through the booth?  If that's indeed a necessity, would it be easier to install a simple rheostat controller in place of the on/off switch?

Honestly, I had considered a rheostat, but I wasn't sure how it might affect the blower motor. Do they typically hold up well when controlled with a rheostat? My reasoning for wanting that functionality is simply to cover my bases. If it happens that the fan I use pulls more than I'd like (I'm sure it's possible), it would be nice to reduce airflow as necessary. Also, when drying, it would be nice to back it off to reduce the amount of dust that might be drawn in.

styrene wrote:

Rich.Carpenter wrote: I've not completely settled on mounting the filter inside the booth. I'm still toying with the idea of building in an exterior accessible slot - possibly with a latched cover - that the filter would slide into. Great idea.  Sure makes for quick and easy change-outs.

Sure would. Only trouble is that design looks much easier on paper than in implementation. We'll see how the build goes. I've already started over this evening, as the more the project came along, the more "pieced together" it was getting. I saw several areas where a little more forethought would have provided a lot more structural integrity. Also, providing nailing surfaces around the edges of the plenum chamber ended up being a bit of a jury-rigged afterthought. I just wasn't happy with the way it was going together. The second time around is working out much better.

styrene wrote:

Just one additional suggestion:  Make sure the attachment points for your fan, and your plenum box are completely sealed.  Nothing destroys airflow quicker than leaks.  Consider gluing your joints, and then caulking everything.

I definitely considered that. All joints are getting glued and nailed. I'm also putting it together in a manner that will allow me to caulk the plenum chamber mid-construction, while I can still get into it.

Thanks loads for the suggestions!

Rich.Carpenter wrote:

Honestly, I had considered a rheostat, but I wasn't sure how it might affect the blower motor. Do they typically hold up well when controlled with a rheostat? My reasoning for wanting that functionality is simply to cover my bases. If it happens that the fan I use pulls more than I'd like (I'm sure it's possible), it would be nice to reduce airflow as necessary. Also, when drying, it would be nice to back it off to reduce the amount of dust that might be drawn in.

Rich, I've dealt with rheostat-controlled chemical laboratory hoods and both permanently mounted and portable dental workstation hoods (prosthetics labs) and haven't noted any problems with any of them from a controller/motor standpoint.  If you're still concerned, you could always call the fan manufacturer and ask them if there are potential problems with installing a rheostat.  As an alternative you might consider mounting a temporary filter that would cover the face of the hood, which would provide dust control during drying times.  Depending on the filter type, airflow fall-off should be minimal, so you would still benefit from maximum airflow, reduced dust, and faster drying times.

By the way, I really like your in-progress pics, and your basic plan pics.  Looks like you have a really nice project underway.

Gip

I found some 110v puck lights today. They use 20w xenon bulbs. Anyone ever used these? I've heard they get pretty hot. Anyone have any idea if three of them across a 28" (probably spread across the middle 12-14") space will provide good quality lighting at about 15" above the workspace?

Rich.Carpenter wrote:

I found some 110v puck lights today. They use 20w xenon bulbs.  I've heard they get pretty hot.

Anyone have any idea if three of them across a 28" (probably spread across the middle 12-14") space will provide good quality lighting at about 15" above the workspace?

That's exactly what I needed to know. Thanks, wimpy!

As far as mounting the fan, I ended up mouting my fan off-center because of the way you oil the motor. (The fan needed to mounted on its side.) I have no data other than the practical use of my booth, I can't see any problems with the fan mount. (photos of the final design found at this link...)   /forums/1161407/ShowPost.aspx  I believe (I can't quantify my statement) that the filter itself does a bulk of the distribution of the air in the plenum. Even if there is a slight more draw to one side or the other, then so be it. It draws off the fumes and doesn't seem to impact my spraying.

 Yea, I know that I could have mounted the fan on the back center but that made storing the booth impractial for me. 

Updated Link:  /forums/1161407/ShowPost.aspx
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That's good to hear, Wrinkledm. I hadn't seen a booth designed this way, and really wasn't sure what to expect.

By the way, the URL you provided doesn't appear to be correct.

Thanks!

Well, with spring well underway, and summer upon us, I'm finally getting back to working on my booth. I went to Grainger today and picked up a 1TDS2. It's a bit bigger than I was expecting, but I should be able to make it work just fine. The fact of the matter is that I walked in planning to buy a 1TDR7 (485 CFM), but they didn't have one in stock, so they showed me the 1TDS2 (549 CFM). After the wholesale discount, I was able to get it for about what I was expecting to pay for the 1TDR7, so I was happy.

The booth is all but ready for the exterior panels and lighting to be installed. I'll try to get some more pics posted soon.

Edit: One other thing. I've read that blowers will move air more effectively from the exhaust end of the duct (better pulling air than pushing it). Therefore, I plan to mount it to a window panel and run the 6" duct directly to the bottom of the cabinet. We'll see how that goes.