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Exhaust Fan advice needed

#1
Hi, I've been doing epoxy and high build work in my home spray booth without any great issues, but now that I'm doing base/clear, I'm having trouble getting rid of the "fog" from the clear. I did the chassis yesterday, which takes a lot of spraying to get all sides of the chassis and crossmembers etc. The base exhausts ok. The fan I use is rated at 1990 CFM and pulls hard. I use three layers of pre-filters (about 1/2" thick, plus activated carbon filter to help remove fumes. The pre-filters get clogged with clear pretty quickly, so be the third coat of clear, they're pretty plugged up. It's still exhausting, but I get a pretty heavy fog in the booth. I'm using an Iwata 400 lpx HVLP gun. I could change the pre-filters between coats, but don't like to disturb things between coats. Is 2000 CFM way undersized? The booth is 10'x24'x10' ceiling. I'm an amateur obviously, but would like to improve conditions if I can. Thanks, Bill
 
#2
Your frame looks awesome. Can you provide a little more information regarding how you pull air into the booth and how you exhaust it out of the booth?
 
#3
I have three 20x20 supply filters on one end of the booth and this 1990 CFM negative air fan and filter at the other end, which exhaust through the outside wall. The incoming air is pulled from outside into the other side of the shop and from there through the filters into the booth.
 
#4
i use single layer dry filters on my exhaust.. they are easy to change while fan is going if need be but never had to change ..
 
#5
LxWxH =cubic feet that answer gives you the cfm of a fan to replace all the air in a given space in 1min. That is of course if you have free intake air (no resistance) if you have resistance it will cause your fan to strain and will create negitave pressure which you do not want in a booth. You have to figure the intake air flow to make sure it is adequate.and equally spread out for even flow.

For a Pro booth it can get involved but for home use I like to see the air exchange in the area of every 45-30sec. Having a fan that can be controlled by
a rheostat switch (like mine) makes it easy to control the draw exactly where I need it.

Having all those filters in front of your fan I'm sure is choking it (have a pic of the fan setup?). You should have a filter wall or column with multiple filters to spread the exhaust demand.
 
#6
You can also do what Shine suggested and change them with the fan going. I would have a garbage bag with me and place it in it as soon as I took them down so no specks of trash got on the project.
 
#9
I'm looking at a house that has a 30x50 building and a 14x24 RV storage. Neighbors are a little close and of unknown demeanor.
 
#10
Thanks for all the comments. I am using activated charcoal filters in my exhaust which removes the lion's share of the odor. None of my neighbors can see what I'm doing, but they all kind of know, we've all been neighbors for 20 years or more. I can't really vent into the building. although I could vent into a large attic area, but I'm not crazy about putting all those fumes up there. I think increasing the surface area of the exhaust filter would likely help. Right now the exhaust fan just has about 3 square feet of surface area. I'm thinking about adding another fan of the same capacity, and run them slower, which would double the surface area of the exhaust filters. Right now it pulls so hard I can get clear drips at the base of the filter from the build up.
 
#12
DATEC
"Having a fan that can be controlled by a rheostat switch (like mine) makes it easy to control the draw exactly where I need it."

What fan do you use that can be controlled by a rheostat switch and what switch are you using? I need to set something up in my garage and wanted to vary the speed of the fan accordingly and thought a simple rheostat would burn out the motor if not matched properly.
 
#13
I've been using a Jenny fan. I also found out that I didn't have enough air movement so I'm in the process of adding a second one next to the floor. The have both fixed and variable speeds along with different sizes.
 
#15
My fan (3 speed) & louvers came from McMaster Carr. They have a good selection. I also went to a reusable filter that just rinses out. It seems to allow better airflow than the disposable paper ones do.
 
#16
bill3337;n80419 said:
Thanks for all the comments. I am using activated charcoal filters in my exhaust which removes the lion's share of the odor. None of my neighbors can see what I'm doing, but they all kind of know, we've all been neighbors for 20 years or more. I can't really vent into the building. although I could vent into a large attic area, but I'm not crazy about putting all those fumes up there. I think increasing the surface area of the exhaust filter would likely help. Right now the exhaust fan just has about 3 square feet of surface area. I'm thinking about adding another fan of the same capacity, and run them slower, which would double the surface area of the exhaust filters. Right now it pulls so hard I can get clear drips at the base of the filter from the build up.
Don't even think of venting inside a building of any size. As far as you getting clear drips at the base of the fan, I have never had that happen you really need to get is straightened out before something bad happens. I have seen booth filters spontaneously combust because of build up after extended use and being caked but to have them that soaked with material not good.
 
#17
ksungela;n80427 said:
DATEC
"Having a fan that can be controlled by a rheostat switch (like mine) makes it easy to control the draw exactly where I need it."

What fan do you use that can be controlled by a rheostat switch and what switch are you using? I need to set something up in my garage and wanted to vary the speed of the fan accordingly and thought a simple rheostat would burn out the motor if not matched properly.
http://www.ebay.com/itm/New-Fantech-...item43c972a7bb

I got mine for 299.00 and bought a 5A speed control for a house ceiling fan (it was what the company tech said to get when I called) works great. The speed control is the one with the round knob. If you try and control a fan not designed for that it will get hot and shut down (thermal overload). This fan is alum. so it won't spark and can run full blast to create one hell of a breeze on those hot calm days or run at a creepy crawl and everything in between. I got the 24" to go into an existing window of my garage perfect size for me.

As for being explosion proof for home use it will be fine the total sealed motor IMO is good enough the explosion proof fans have their place mostly commercial due to everyday use and everyday painting but for at home this is just fine.
 
#18
DATEC;n80451 said:
http://www.ebay.com/itm/New-Fantech-...item43c972a7bb

I got mine for 299.00 and bought a 5A speed control for a house ceiling fan (it was what the company tech said to get when I called) works great. The speed control is the one with the round knob. If you try and control a fan not designed for that it will get hot and shut down (thermal overload). This fan is alum. so it won't spark and can run full blast to create one hell of a breeze on those hot calm days or run at a creepy crawl and everything in between. I got the 24" to go into an existing window of my garage perfect size for me.

As for being explosion proof for home use it will be fine the total sealed motor IMO is good enough the explosion proof fans have their place mostly commercial due to everyday use and everyday painting but for at home this is just fine.
Do you have any photos of your set up anywhere on the site?
 
#19
DATEC;n80450 said:
Don't even think of venting inside a building of any size. As far as you getting clear drips at the base of the fan, I have never had that happen you really need to get is straightened out before something bad happens. I have seen booth filters spontaneously combust because of build up after extended use and being caked but to have them that soaked with material not good.

Moving to much air if you are forming drips on the fan. 100 ft per minute is the baseline flow rate for a cross flow booth.


http://www.binks.com/resources/tip-of-the-week/how-do-you-calculate-spray-booth-airflow
 
#20
Senile Old Fart;n80626 said:
Moving to much air if you are forming drips on the fan. 100 ft per minute is the baseline flow rate for a cross flow booth.


http://www.binks.com/resources/tip-of-the-week/how-do-you-calculate-spray-booth-airflow
That's true but that is for pro booth set-ups and alot more math is required along with trained professionals (I can get you in touch with my buddy http://www.bciequipment.com/ that does that if you like) with the proper measuring equipment and will come in with smoke sticks to adjust air flow and flow cavatation etc. But for a home garage set-up using just the basics for fume extraction will be fine.
 
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