Manufacturers' Digest

DOE-HDBK-1092-98

5.5 MANUFACTURERS' DIGEST

Manufacturers produce NEC code digests for selection of seals and drains and provide, by class and

division, catalog data and installation diagrams for their use in electrical power and lighting systems

in hazardous areas. The manufacturers' NEC code digests should be in compliance with current

NFPA/NEC requirements. The two that are most used are as follows:

1. Crouse-Hinds ECM Code Digest

2. Appleton's NEC Code Review.

5.6 DESCRIPTIONS, FEATURES, AND TEST CRITERIA OF

ENCLOSURES FOR HAZARDOUS (CLASSIFIED) LOCATIONS

(PER NEMA 250)

Type 7 and 10 enclosures, when properly installed and maintained, are designed to contain an internal

explosion without causing an external hazard. Type 8 enclosures are designed to prevent combustion

through the use of oil-immersed equipment. Type 9 enclosures are designed to prevent the ignition

of combustible dust.

As mentioned earlier, hazardous locations (other than in mines) are classified according to the

flammability or combustibility of the materials that may be present and also according to the

likelihood that a flammable or combustible concentration is present. For definitions and classifications,

see the NEC, Article 500, and NFPA 497M, "Classification of Gases, Vapors and Dust for Electrical

Equipment in Hazardous Classified Locations." Descriptions and tests in this standards publication

cover equipment that is suitable for installation in locations classified as Division 1 or 2. In Division 2

locations, other types of protections and enclosures for nonhazardous locations may be installed if

the equipment does not constitute a source of ignition under normal operating conditions. See the

specific sections of Articles 501 through 503 of the NEC.

Intrinsically safe equipment (not capable of releasing sufficient electrical or thermal energy under

normal or abnormal conditions to cause ignition of specific hazardous atmospheres) may be installed

in any type of enclosure otherwise suitable for the environmental conditions expected. See ANSI/

UL 913, "Intrinsically Safe Apparatus and Associated Apparatus for Use in Class I, II, III, Division

I, Hazardous (Classified) Locations" for detailed requirements.

Purged and pressurized equipment should be installed in enclosures suitable for nonhazardous

locations. Hazards may be reduced or eliminated by adequate positive pressure ventilation from a

source of clean air in conjunction with effective safeguards against ventilation failure. See NFPA

496, "Purged and Pressurized Enclosures for Electrical Equipment in Hazardous Locations" for

detailed requirements.

5.7 TYPE 7 ENCLOSURES

Type 7 enclosures are designed for indoor use in locations classified as Class I Groups A, B, C, or

D as defined in the NEC.

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