Electrical Contractor - September 2017

I L L U S T R AT I O N S B Y C H A R L E S R . M I L L E R

COD E IN F O C U S BY CHARLES R. MILLER

Part I, General, includes Articles 110. 1 through 110. 25. Topics covered include installation and use, listing of equipment, voltages, conductors, wiring methods, interrupting rating, selective coordination, mechanical execution of work, mounting and cooling of electrical equipment, electrical connections, arc flash hazard warning, markings, identification of disconnecting means, available fault current, and lockable disconnecting means.

Part II includes Articles 110. 26
through 110. 28. While Part II contains
only three sections, two of them contain
a number of subsections. Part II contains
provisions for electrical systems rated

1,000 volts (V), nominal, or less. Prior to the 2017 NEC, the voltage threshold for this part was 600V, nominal, or less.

Part III contains provisions for electrical systems rated more than 1,000V, nominal, includes 110. 30 through 110. 41.

Part IV covers tunnel installations
more than 1,000V, nominal. It also con-
tains provisions for the installation and
use of high-voltage power distribution
and utilization equipment that is portable,
mobile or both, such as substations, trail-
ers, cars, mobile shovels, draglines, hoists,
drills, dredges, compressors, pumps, con-
veyors, underground excavators, and the
like. Provisions in Part V—the last part
in Article 110—apply to installations in
manholes and other electrical enclosures
intended for personnel entry.

Enclosures for electrical installations are covered in 110. 31, which is divided into four subsections: (A) electrical vaults, (B) indoor installations, (C) outdoor installations, and (D) enclosed equipment accessible to unqualified people. The provision pertains to conductors and equipment rated over 1,000V, nominal. Section 110. 31(B) pertains to indoor installations and is divided into two subsections. In accordance with 110. 31(B) ( 1), indoor electrical installations that are accessible to unqualified people shall be made with metal-enclosed equipment. Switchgear, transformers, pull boxes, connection boxes and other similar associated equipment shall be marked with appropriate caution signs.

It may be necessary to refer to Article 490 when referencing requirements in Part III of Article 110. Article 490 covers the general requirements for equipment operating at more than 1,000V, nominal. In accordance with 490.30, Part III covers assemblies of switchgear and industrial control equipment including, but not limited to, switches and interrupting devices and their control, metering, protection and regulating equipment where they are an integral part of the assembly, with associated interconnections and supporting structures (see Figure 1).

The last sentence in 110. 31(B)( 1) states that openings in ventilated dry-type

Article 110

ARTICLE 110 IN THE NATIONAL ELECTRICAL CODE (NEC), covers general requirements for the examination and approval, installation and use, access to and spaces about electrical conductors and equipment; enclosures intended for personnel entry; and tunnel installations. It contains five parts.

General Installation Requirements, Part XXXII
FIGURE 1 INSTALLATIONS ACCESSIBLE
TO UNQUALIFIED PERSONS

Indoor electrical installations accessible to unqualified people shall be made with metal-enclosed equipment [ 110. 31(B)( 1)].

Switchgear, transformers, pull boxes, connection boxes and other similar associated equipment shall be marked with appropriate caution signs [ 110. 31(B)( 1)].

Enclosures for electrical installations are covered in Article 110. 31, and these provisions pertain to conductors and equipment rated over 1,000V, nominal.