Hello all,
i have to agree and disagreee with a couple of things said about the fan used on the spray booth.
I agree that an explosion proof motor would be best but dont stop at the motor. The fan would also have to be made of something other than steel to keep from rubbing together and causing sparks. Typically the fan blade would be aluminum to keep from sparks. dont forget also that any light switch or other switches can cause sparks and ignite the solvent.
Also, from what i have read and have been told, dont some water based products have alcohol ?
You could put the fan outside the wall, pipe the vapors into the inlet of the fan and directly vent the output outside. This would isolate the motor more from the vapors, but still would not be explosion proof.
I disagree about the comment that the motor had brushes. If the fan and motor came out of a house hvac unit, the motor should be a Permanant split phase motor. you can tell if it is by looking for the Oil can capacitor, oval or round silver can. These motors have no brushes, or mechanical switches to cause sparkes.
You also have to be careful in using these types of fans because the need a certian amount of back pressure. If you dont load the fan enough, the motor and overheat and burn up. It would be a good idea to check the current draw after it is running , and compare it to the motor nameplate.
A standard single phase motor has a black round capacitor and an internal mechanical switch that kicks in and out at about 2/3 speed. (larger motors may have a black capacitor and an oil can capacitor) I would not recomend using these motors because of the big spark emitted during switching of the cap's.
Typically the only motors with brushes should be power tools, vacuums, routers drill and etc. (called universal motors because they can run on single phase ac or dc).
Thanks,
curt