Stumped by the Code? NEC Requirements for Documentation of Hazardous Locations

All questions and answers are based on the 2020 NEC.

Q. What techniques does the Code require for the protection of electrical and electronic equipment in hazardous (classified) locations?

A. Electrical and electronic equipment in hazardous (classified) locations must be protected by one or more of the following techniques [Sec. 500.7]:

(A) Explosionproof Equipment. Explosionproof equipment is permitted in any Class I location for which it is identified (See Figure.)

Explosionproof equipment is designed to be capable of withstanding and containing the force of an internal explosion, and the hot gases within the enclosure cool as they escape [Art. 100].

(B) Dust-Ignitionproof Enclosures. Dust-ignitionproof enclosures are permitted in any Class II location.

Dust-ignitionproof enclosures are designed to exclude dusts and will not permit arcs, sparks, or heat within the enclosure to cause the ignition of exterior dust [Art. 100].

(D) Purged and Pressurized Systems. Purged and pressurized systems are permitted for equipment in any hazardous (classified) locations for which they are identified.

(E) Oil-Immersed Contacts. Oil-immersed make-and-break contacts can be installed in a Class I Division 2 location.

(F) Hermetically Sealed Contacts. Can be installed in Class I, Division 2; Class II Division 2; or Class III, Division 1 and 2 locations.

“Hermetically Sealed” is when equipment is sealed against the entrance of an external atmosphere, where the seal is made by methods such as soldering, brazing, welding, or the fusion of glass to metal [Art. 100].

Q. What is the Code requirement for documentation of hazardous (classified) locations?

A. All areas designated as hazardous (classified) locations must be properly documented. The documentation must be available to those who are authorized to design, install, inspect, maintain, or operate the electrical equipment [Sec. 500.4].

Proper documentation of hazardous areas assists the designer, installer, and authority having jurisdiction (AHJ) in ensuring adherence to the stringent requirements contained in Arts. 501 through 517.

To assist in compliance with the above requirements, some AHJs require drawings that indicate hazardous (classified) location areas and their classification(s).

The NEC does not classify specific hazardous (classified) locations in Arts. 511 through 517, unless identified as such in the Articles. Determining the classification of a specific hazardous area is the responsibility of those who understand the dangers of the products being used, such as the fire marshal, plant facility engineer, or insurance underwriter. It is not the responsibility of the electrical designer, electrical contractor, or electrical inspector. Before performing any wiring in or near a hazardous (classified) location, contact the plant facility and design engineer to ensure that proper installation methods and materials are used. Be sure to review Sec. 500.4(B) for additional standards that might need to be consulted.

These materials are provided to us by Mike Holt Enterprises in Leesburg, Fla. To view Code training materials offered by this company, visit www.mikeholt.com/code.