Brushed Motors in Class 1 Div 2 Area

[aanvari3]

Sorry, I probably asked this in the wrong thread yesterday:

We are installing a 20 HP 115 VDC motor in a Class 1, Div 2, Group D building. Because of the voltage, we are only able to refurbish an existing TEFC motor, so we don't have an explosion proof one. This motor has brushes, if they are in the enclosure thats fan cooled does this allow the motor to go in the hazardous area? Or since the brushes create sparks, we would need an explosion proof enclosure?

Reading NEC 501.125(B)'s paragraph "In Class 1, Div 2 locations, the installation of nonexplosion proof enclosed motors such as squirrel-cage induction motors WITHOUT BRUSHES or other arc producing devices are permitted" leaves me to believe i'm gonna have to get an explosion proof one. The terminal housing, however, is explosion proof with epoxy sealing for the motor leads into the enclosure.

 

[rbalex]

Sorry, I probably asked this in the wrong thread yesterday:

We are installing a 20 HP 115 VDC motor in a Class 1, Div 2, Group D building. Because of the voltage, we are only able to refurbish an existing TEFC motor, so we don't have an explosion proof one. This motor has brushes, if they are in the enclosure thats fan cooled does this allow the motor to go in the hazardous area? Or since the brushes create sparks, we would need an explosion proof enclosure?

Reading NEC 501.125(B)'s paragraph "In Class 1, Div 2 locations, the installation of nonexplosion proof enclosed motors such as squirrel-cage induction motors WITHOUT BRUSHES or other arc producing devices are permitted" leaves me to believe i'm gonna have to get an explosion proof one. The terminal housing, however, is explosion proof with epoxy sealing for the motor leads into the enclosure.

You have cited the correct reference clause.

Technically, the motor only needs to be identified for Class I, Division 2 but effectively that means a Division 1 motor or, if you're up to something more exotic, a purged one. In this case though, purging can be "painful" when complying with all of the requirements of NFPA 496, even for a Type Z design especially if the motor starts frequently - but it does work. I've only done it once (well over 30 years ago) for a 2000hp, brush-type synchronous motor, but there the economics were worth it - once it started, it ran until the next plant shutdown, usually around 4 years. To my knowledge, it's still working.

You should be aware that most explosionproof motors, but certainly not all, are basically standard TEFC or TENV motors with modified enclosures, possibly with an integral thermal switch in the windings. On the positive side the frame size is usually the same or one size larger per a given manufacturer's horsepower.

The reason the motor only needs to be identified is that very few manufacturers have their motors listed for Division 2 since most standard three-phase induction motors are suitable.When used in Division 2, most single-phase and dc motors are listed for Division 1.