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501.10(B)(1) Wiring Methods. Class I, Division 2.,

Code Change Summary: Changes were made to the allowable wiring methods used in a Class I Division 2 location.

Article 501 is all about Class I hazardous locations. The Class represents the type of flammable material, whereas the Division represents the conditions where the flammable materials are used or stored and the likelihood of the flammable material being present.

Examples of Class I locations include fuel dispensing, spray booths where volatile flammable solvents are used, gas generator rooms and other portions of gas manufacturing plants where flammable gas may escape.

Section 501.10(A) specifies all of the types of wiring methods permitted to be used in a Class I Division 1 hazardous location. Those methods are also permitted to be used in a Class I Division 2 location which is less restrictive than a Division 1 location. Two of the allowable wiring methods for a Class I Division 1 location are threaded rigid metal conduit (RMC) and threaded steel intermediate metal conduit (IMC).

In the 2017 NEC, revisions were made to 501.10(B), pertaining to Class I Division 2 locations, to allow RMC and IMC with listed threadless fittings. Requiring only threaded fittings as in 501.10(A) was too restrictive since many cable types permitted in Class I Division 2 locations were only required to use listed fittings. Many listed cable fittings are threadless and permitted in Class I Division 2 locations.

Another change was the addition of Cablebus to the permitted wiring methods in a Class I Division 2 location. Cablebus is similar to cable tray with spacers between the conductors. Since tray cable is allowed in a Class I, Division 2 location, there is no reason a cablebus with insulated cables shouldnt also be allowed.

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2014 Code Language: 501.10(B) Class I, Division 2.

(1) General. In Class I, Division 2 locations, the following wiring methods shall be permitted:

(1) All wiring methods permitted in 501.10(A).

(2) Enclosed gasketed busways and enclosed gasketed wireways.

(3) Type PLTC and Type PLTC-ER cable (see NEC® text for remainder).

(4) Type ITC and Type ITC-ER cable as permitted in 727.4 and terminated with listed fittings.

(5) Type MC, MV, TC, or TC-ER cable (see NEC® text for remainder).

(6) In industrial establishments with restricted public access (see NEC® text for remainder).

(7) Optical fiber cable Types OFNP, OFCP, OFNR, OFCR, OFNG, OFCG, OFN, and OFC (see NEC® text for remainder).


2017 Code Language:501.10(B) Class I, Division 2.

(1) General. In Class I, Division 2 locations, all wiring methods permitted in 501.10(A) and the following wiring methods shall be permitted:

(1) Rigid metal conduit (RMC) and intermediate metal conduit (IMC) with listed threadless fittings.

(2) Enclosed gasketed busways and enclosed gasketed wireways.

(3) Type PLTC and Type PLTC-ER cable in accordance with the provisions of Article 725, including installation in cable tray systems. The cable shall be terminated with listed fittings.

(4) Type ITC and Type ITC-ER cable as permitted in 727.4 and terminated with listed fittings.

(5) Type MC, MV, TC, or TC-ER cable, including installation in cable tray systems. The cable shall be terminated with listed fittings.

(6) In industrial establishments with restricted public access (see NEC® text for remainder).

(7) Optical fiber cable Types OFNP, OFCP, OFNR, OFCR, OFNG, OFCG, OFN, and OFC (see NEC® text for remainder).

( Cablebus.

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