The Stovebolt Site Forums The Shop Area Paint and Body Shop Paint Booth Design

I am preparing to build a temporary paint booth inside my garage and have looked at a few of the U-Tube videos to get an idea what others have done.

I have a blower from a furnace I am planning to use to push filtered air into the booth with filters on the opposite end where air can exit the booth, but I do not know if that is enough or a good approach. I an hoping to have a slight positive pressure in the booth to avoid pulling in unfilter air from the surrounding area.

I want the ceiling of the booth to be high enough to be able to spray the top of the cab without feeling constrained by the booth.

I am not sure what other aspects of the booth design I need to consider and would appreciate input from those that have done their own version of a paint booth about size, air flow, and anything else that I may be failing to consider.

I used a furnace fan years ago but used it in reverse of what you are describing .i used it to suck the air out (overspray) and had the bottom of the garage door open a inch or so to allow air in with a wet floor .Blowing air in would it not stir up a lot of dust .Also used a filter on the furnace fan to catch the paint so no one would get overspray in the area.

I'd go with a fan pushing air into a plenum with a bank of filters going into the booth proper, and additional filters on the opposite end to catch the overspray. Getting the velocity of the incoming air down is key to keeping dust down. Of course you'd want to do a washdown of the floor.

Kevinski, my concern with using the fan to suck out the air (and fumes) is that the motor on the fan is nothing special and I don't want to risk volatile materials being exposed to the motor. I am hoping (maybe wishfully) that I can avoid blowing dust around by filtering the incoming air and having the booth pretty clean before I start.

Klhansen, did you mean that getting the veloicty of the incoming air DOWN is key? I assume that the low velocity would help minimize the potential to kick up dust. I was not anticipating a plenum but that is a good idea to avoid both high velocity and the potential for a lot of differences in air flow throughout the room. I will probably still use a filter on the intake side of the fan to minimize the amount of dust etc. that otherwie would be influencing the plenum exit filters.

I assume that the wet floor is also to keep dust down.

Commercial paint booths are built with what's called laminar flow down the length of the booth. Enough air volume pumped through so there's a nice gentle flow down the booth length. Your concern about the fan motor not being rated as explosion-proof is valid. If you had a fan with an explosion-proof rating, then I'd say use it to exhaust air from the booth with a wall of filters on the intake side, and good door seals to keep stray air from leaking in and potentially stirring up dust. Yes, dampening the floor is to keep dust down.

FWIW, I painted my truck inside a tent, with little dust protection other than wetting the floor underneath. I had very little issue with dust nibs on the finish.

I suspect I am going overboard on my paint booth design given that it is intended to be a temporary setup but I am having trouble finding a good balance between good and good enough.

Maybe I'm just lucky, but I've painted a couple of times with no air flow. I chose to paint with it in parts, not assembled, which may be part of it. I have a fresh air system to my mask though. Never had an issue with overspray or dust. I have only used single stage non-metallic which is easier matching parts painted at different times. The next time though, I'm considering an explosion proof exhaust fan. That would take care of the overspray seeping into everywhere. Oh, and I staple up plastic sheets top, sides, floor. The compressor was in another room so I didn't blow the place up. It worked for me.

Dennis

Never had a problem with the blower motor but I only painted about 6 cars in the past. Can’t remember if the furnace filters used to filter the over spray were on the inside or outside but remember it was a sheet metal box big enough for two or three 20/25 filters. I think the fan blowing in will stir up a lot but if you can block it off and make it so it doesn’t blow like a hair dryer then I guess it may work. I also did a few other things when I painted like putting a chain over the tailpipe. Don’t know if this did anything but grounded the vehicle from being on tires. The compressor I used got warm so I also would use copper pipe from the compressor to the tank curled up and around going into a five gallon bucket of water the water would be warm after painting and also wet the floor with a broom. This was my redneck way but it worked for me.

A little info to help with your decision, the vast majority of the residential furnace blower motors are induction ac, no brushes to create a spark, and no start capacitor to connect and disconnect that could create a spark. I'm not saying that they are enclosed, or drip-proof, just that there is an extremely slim chance of that type of motor causing an explosion. I would bet that static electricity from plastic sheeting, dry conditions, or a light switch arcing has a higher chance of causing trouble.

If the furnace blower motor operates on single phase power, it HAS to have a start capacitor and a start/run switch. Otherwise it will just sit and hum. If it's a 3-phase motor (not very likely,) then what 78buckshot said would be true.

I suppose we should describe the type of blower being used. My assumption is that WICruiser is using a salvaged blower assembly from a modern furnace. In this case the blower motor is most likely a direct drive, where the blower wheel is attached directly to the motor shaft. This type of motor is called a permanent split capacitor (PSC) motor, it does not use a separate start capacitor and therefore will not arc in order to drop out a start device. If by chance the blower is a belt drive from an older style of furnace, it could have a separate start capacitor and drop-out switch which would produce a spark upon opening. It is true also that if it is a 3 phase motor as klhansen noted, it will not have a start or run capacitor, if WICruiser has 3 phase in his garage, I want to rent a bay or two. If WICruiser could post a picture of his intended blower, we probably can advise.

I do not have 3 phase and the blower is from an older furnace with the belt drive setup. The motor is actually from something older that I had laying around so it definitely has a start capacitor, etc.

I think with the blower pushing air into a plenum that has a 90 degree turn to the exit and a lot more exit area than the intake side of the blower the exit velocity into the booth should be pretty low. I also plan to have filters on the plenum discharge to help even out the distribution. There is a fair amount of air moved by the blower but the disharge area is only about 18" x 6" sow if I have a plenum with 4 24x25 filters the veleocity should be pretty low in the room.

I considered just having a static room but I have the blower on hand it seemed like a good idea to use it.

It will take some time to build but I need warmer temperatures before I can paint so it may work out.

I am planning to paint parts, or at least areas of parts seperately then paint the whole truck once it is assembled. I choose a non-mettalic paint with hopes that it would work better for this approach.

I think your plan will be fine, you won't need or want a large air turn-over, just enough to gently keep the haze under control. Too much air movement will affect the appearance of the paint from panel to panel, it also makes it more difficult to control the temperature.

Thank you all for your input.

A used smoke ejector (for firefighting) is explosion proof, might be an option for you..


https://www.facebook.com/share/1XDPogthwf/

An intersting idea but I am hoping to avoid spending more on this project and already have an old furnace blower unit I am planning to incorporate.