Fan Placement in Paint Booth

Hi, Rick.

The dimensions of your booth face (28" X 20" = 3.9 square feet), and a recommended capture velocity of 100 fpm suggest a fan rated at a minimum of 400 cfm.  I don't think 4" ducting over a 36" run is going to add significant resistance to that fan setup unless you are going to have right angle bends every foot; however, with the additional paint filter (get a good one), you may want to consider a 450cfm rating for a fan.

The fan should be mounted on the rear of the booth unless you intend to install an angular baffle inside the booth, in which case you can mount the fan on top of the booth at the back.  A rear-mounted fan will provide more laminar airflow throughout the booth.  The addition of a vertical baffle in front of the fan will distribute the airflow even better.  The recommended distance in front of the fan inlet to the baffle is 0.75 X duct diameter, or 3". 

Hope this helps some.  Good luck with your build and keep us posted on the outcome.

Gip Winecoff

Because fans do a better job of sucking air, placing the fan as close to the exhaust end of the system the better. Fans loose their effeciency pushing air down/through a long tube. Hence the reason dust collection systems have the fan and motor as close to the collection resevoirs.

Like this industrial application:

Or this workshop one:

The added benefit is you can locate the fan away from your work area which means its quieter. 

Maybe this will help you...

http://modelpaint.tripod.com/booth2.htm

Tony

Nice sized booth! Spraying on the patio should need nothing more than a particle mask for you.

4" is a bit small when you move inside, though. That will move less than 40 CFM.

For the size of your booth, I suggest a minimum of a six inch outlet.......(many, many fan options) which will move over 100CFM.

Many people are particular about particulates! Listen to advice and wear a mask if you are worried. But a six inch (round pipe) exhaust will move all of the air you need moved. Buy a fan that moves at least 500 CFM and you should be fine.

Unless you're painting a  full-sized A/C....MY opinion is that you will have no fumes.

I prefer venting from the top of the booth for ease of installation.....but down draft is great if you can do the work!

HTH 

Thanks - excellent follow-up questions.

Current plan:

- L x W x H:  28" wide (width of front opening) x 18" deep x 20" high

- I'm planning on using on my patio, so it would be probably vented through an 36" run with 4" diameter duct from the fan to the vent point (which in this case would be to simply a distal point on the patio just to direct away from booth); in the longer term, I will move to garage shop (project to completed), and then I would have about the same amount of run to the outside through a wall.

- I'd like to plan for a filter 

Hope this helps.

Cheers, Rick

Richard....this topic hits often......and we all have our own opinions and reasons

What will help with me and others that answer.....how  big is the booth Height, Width and Depth?

How do you plan to vent it.....out a window?....thru a wall?......thru a filter?

....And how far from the vent point is the booth?

Knowing this will get you great answers!