Chapter 8 - Electrical equipment for NEC Class II, Group F locations

Abstract

The chapter focuses on Class II divison 1 and division 2 Locations. Electrical equipment must be installed in dust-ignition proof or dust-tight enclosures or in enclosures that minimize the entrance of dust. Dust-ignition proof enclosures will exclude the entrance of dust and also prevent arcs or sparks from igniting combustible dust in the air surrounding the enclosure. Arcing devices— such as, switches, circuit breakers, fuses, push-button stations, relays, etc., must be enclosed in dust-ignition proof enclosures when the electrical equipment is located in a hazardous area. The wiring method for hazardous locations should consist of: fittings and boxes that are designed to minimize the entrance of dust, and are provided with threaded bosses for connections to threaded rigid metal conduits, or Type MI cable with approved terminal fittings, or dust-tight flexible connections approved for the location. The fittings and boxes should have no openings through which dust might enter, or through which sparks or burning material might escape. The wiring method for NEC Class II, Division -2 locations including: wire ways, fittings and boxes with terminals, splices, and taps also require a design that minimizes the entrance of dust. If dust accumulation is heavy, any type of electrical motor may be used in separate dust-free rooms.