Setting up Paint Booth

[seanb02]

Finished up ordering the last couple bits to get everything on the way for this project. Ordered 12 of the 24x24" furnace filters for the intake, I'll have to experiment and see how many filters it takes to get good airflow going since I'm not planning on having a fan on the intake side of things, just the exhaust side on the other end of the booth. Plan on putting the intake filters up high on one end and the exhaust down low on the other side which should give it the best downdraft and cross flow.

Got hung up on the MERV ratings and whatnot of filters during the research process but ultimately decided the cheaper 3m MERV 5 rated ones would probably flow better without having air shoved through by a fan in front of it than a higher rated more expensive filter would. It's not like the plastic is going to perfectly sealed or anything, theres always going to be gaps here and there so the filters just have to remove the majority of the particles.

Also ordered some parachute cord and eye screws to rig up a system for raising and lowering the plastic quickly and easily. Will get some pictures posted as I start installing things.

 

[sberry]

You do NOT shove air in,, you draw it out. There are some commercial booths especially in more complicated buildings that do use a fan for intake but its a matched system to tailor the draw. You don't need or want it here.

 

[seanb02]

You do NOT shove air in,, you draw it out. There are some commercial booths especially in more complicated buildings that do use a fan for intake but its a matched system to tailor the draw. You don't need or want it here.

That's what I figured. What threw me was reading other threads discussing using positive pressure to push air in thus keeping other particles outside of the paint area. Seems to make much more sense to just pull air out since its the overspray and fumes that need removed anyway, without being a totally sealed room there isn't any way to keep every wayward particle out of a paint job, so provided the main intake source is filtered pulling air through the booth shouldn't be an issue.

 

[seanb02]

Decided to move the planned location of the booth area, rather than off to the side where the old chute is located I am going to put it clear in the back of the shop but square in the middle between the columns. Couple reasons for this change, not every tractor coming into the shop is able to drive in under its own power, thus screwing around trying to get it into place between the columns could prove difficult. One particular tractor won't fit under the support beam, it only fits down the main runway of the shop. Also being clear in the back of the shop will be less impact to the rest of the shop productivity when there is painting going on.

So I moved the pesticide storage locker off to the side where I was originally planning on putting the booth, and then put the old 50 Ford pickup off to the side in the back. Changed the configuration of the ladder storage rack and cleaned out everything towards the rear of the shop. Waiting on setting up another storage location for some large timbers that are stacked back there before I can go any further. For venting I'm going to put a 12" hole in the second story floor, run a duct down to floor level in the shop, then up and out the side up above with an inline fan pulling the air through the ducting.

I think this change in plans will work out much better long term, I'll try and get a few pictures up of exactly where this is going to give you folks an idea and perhaps you will have some more suggestions for me along the way!

 

[like2wheel]

That's what I figured. What threw me was reading other threads discussing using positive pressure to push air in thus keeping other particles outside of the paint area. Seems to make much more sense to just pull air out since its the overspray and fumes that need removed anyway, without being a totally sealed room there isn't any way to keep every wayward particle out of a paint job, so provided the main intake source is filtered pulling air through the booth shouldn't be an issue.

Having painted in makeshift booths for 47 years I have learned a lot & have to disagree with this. If your ONLY goal is to keep overspray off of things outside of the room this makes sense. But if you are building a room to keep help dirt off of the project you are spraying, you need to supply some filtered make-up air to the room. Ideally slightly more than you are exhausting.

Unless the room can be perfectly sealed, incoming air will take the path of least resistance to replace what is being drawn out. Since there is at least a slight resistance thru even a furnace filter, the bias will be to **** air in thru any gap in your booth first. Typically that is along the ceiling and floor where dirt/dust/cobwebs etc accumulates.
One of the biggest problems is at the door. With that much negative pressure, every time you open the door or curtain, any dirt & dust that you disturb will be sucked in & carried toward the fan. Often landing on your project. The slightest positive pressure would blow that dirt out of the room instead of sucking it in.

Also, rooms with a intake & exhaust fan clear MUCH faster, resulting in less overspray landing on the car.

Unless your only concern is overspray outside the booth, I would at least put a fan outside blowing at your intake filters to help force some make up air thru the filters into your room.

Been there done that.

Edit:
Here is a link to a great fourm for info on any paint project. One of many threads discussing situations like this.
http://autobodystore.com/forum/showthread.php?28482-Garage-Paint-Booth-Ventilation-Question



.

 

[seanb02]

Having painted in makeshift booths for 47 years I have learned a lot & have to disagree with this. If your ONLY goal is to keep overspray off of things outside of the room this makes sense. But if you are building a room to keep help dirt off of the project you are spraying, you need to supply some filtered make-up air to the room. Ideally slightly more than you are exhausting.

Unless the room can be perfectly sealed, incoming air will take the path of least resistance to replace what is being drawn out. Since there is at least a slight resistance thru even a furnace filter, the bias will be to **** air in thru any gap in your booth first. Typically that is along the ceiling and floor where dirt/dust/cobwebs etc accumulates.
One of the biggest problems is at the door. With that much negative pressure, every time you open the door or curtain, any dirt & dust that you disturb will be sucked in & carried toward the fan. Often landing on your project. The slightest positive pressure would blow that dirt out of the room instead of sucking it in.

Also, rooms with a intake & exhaust fan clear MUCH faster, resulting in less overspray landing on the car.

Unless your only concern is overspray outside the booth, I would at least put a fan outside blowing at your intake filters to help force some make up air thru the filters into your room.

Been there done that.

Edit:
Here is a link to a great fourm for info on any paint project. One of many threads discussing situations like this.
http://autobodystore.com/forum/showthread.php?28482-Garage-Paint-Booth-Ventilation-Question



.

Thanks, somehow missed this back when you posted it a few weeks ago! Suppose it will be somewhat of a learning experience, modify as I go and see what works best for my space and application. Not going for showroom quality finishes or anything like that, just a good safe way to spray with minimal mess and help keep the overspray down and junk out of the paint. I can always line up a few regular box fans and point them towards the intake filters to help with air flowing in, but I'll try it with just the exhaust first and see how it goes.

 

[seanb02]

Finally got around to doing some more work on this project yesterday and today, not sure if anybody is interested in seeing the progress, but I'll throw up some pictures anyway. Had to start by fixing the seepage of cow manure through the back wall since that wall is shared with the dairy. Redid the framing, and have it all formed in on the outside to pour a concrete cap to seal it permanently. The hole in the wall was part of the hop drying operation inside of this building, I'm not entirely sure what the purpose was since most of it is below grade. Not even considering using that as potential exhaust port, there wouldn't be any logical way to keep the manure out.

Got most of the OSB sheeting up today, that was quite a workout. Had to get creative and make my own panel lifter on the tractor bucket since I didn't have any assistance. Worked quite well to do it that way. The 12 sheets that are up there now just have 4 or 5 screws each in them to hold in place, will go back and screw them all in solid tomorrow. Also still have to cut a 13" strip for the one side. Overall it's coming along nicely, but the biggest hangup is those old timbers that are parked in the back corner. Can't make the dropdown curtain for that side until they are out of the way. Need to make a space in another section of the barn to put them before they can be skidded out of here.

 

[sberry]

You don't force air in to a booth, it's drawn thru. It's the only way to make it orderly. A ball on has air forced in, leaks anywhere. The dust is only an issue it it's in the mainstream over the paint, leaks between it and the fan don't matter.
There were a couple good tutorials on booth design but I think after reading there wasn't much point in taking the class they were selling. They had good drawings of pressure differentials.
It does take a little trial to tune a make shift booth.
Ideally I like the intake high at one end and the fan low at the other, it creates a contract and dirt kicked up flows along the floor. Mine isn't 100% sealed but where the leaks are don't matter. It's not drawing that air over the paint.

 

[sberry]

Negative pressure. If it's positive or none it blows paint everywhere, doesn't go towards the draw fan. Blows paint, dust, all of it everywhere. Of course the object is to draw overspray and fumes, if it wasn't a guy would simply paint.

 

[sberry]

In that old building will absolutely need to line the room, it would **** dirt everywhere. Having a big enough opening on the room the room is in will help some, won't draw on the cracks. Mine air comes thru orderly enough I don't even filter.

 

[Gerald O]

Negative pressure. If it's positive or none it blows paint everywhere, doesn't go towards the draw fan. Blows paint, dust, all of it everywhere. Of course the object is to draw overspray and fumes, if it wasn't a guy would simply paint.

Above regarding positive pressure is an often repeated total BS paintbooth myth, believed by those that don't understand airflow.

Air always flows from the inlets towards the outlets. Doesn't matter whether the fan goes in the inlet duct or the outlet duct. The only thing the air inside knows is that there's a pressure difference. When the inside is supplied with positive pressure, then the lower pressure of the outside atmosphere is the 'suction'.

As stated before, for the homebuilt booth, positive inside pressure keeps the outside dirt from getting sucked in through the cracks.