NEC 501-8 (b) allows "Open or Non-Explosion proof motors- - - - without brushes or switching mechanisms".
The motor should have an aluminium or plastic fan so that sparking can't occur if the fan accidentaly touches the housing.
Having said that we normally specify XP motors for that classification just to avoid any argument.
Regards
Roy
RoyDMatson nailed it in my opinion. Can use standard motor but non-sparkable, non-metal fan arranged to avoid static buildup / discharge. In the end, though, I recommend going with the XP motor and wiring methods too -- and the client has always agreed.
First, sorry about the delayed response. My week turned to sewage.
All my fans are roof top mounted. I have tube axials and back inclined fans. All are belt drive. All have non-sparking aluminum propellers/wheels. All have standard wiring methods. I was not involved with the inspection process at installation, but I believe the thinking was that it was not posiible to get an ignitable concentration of vapors at the motors. The vapors we are exhausting are heavier than air, so even if the fan fails, you would not get vapors at the motors.
Originally, the tube axials were mounted inside the building. At that time, they had XP motors and wiring methods.
As I read NEC 501.125, section (A) specifies that motors in Class I, Div 1, must be either Identified for the location, pressurized, purged, or special designed. Section (B) does allow open and non XP motors in Class I Div 2 locations. Motor temp should still be considered. The final word is usually with the AHJ. In cases like this, that will probably be both the Electrical Inspector and the Fire Marshal.
If I am understanding the policies properly, I should not provide Vendors and part numbers here. If you want to e-mail me, I can provide the details.
The Axials are number 4C660. The Back inclined fans are 3C494B which has been replaced by 1WBW8. Both have a variety of motor options.
One shortcoming to the tube axial is that the fan belt is in the air stream. Our vapors deteriorate the belts. We tried a number of different belts, but the max life is about 10 -12 weeks (24/7). My preference is the back inclined units.
