General Installation Requirements, Part XXXVI: Article 110

In the 2014 National Electrical Code (NEC), the voltage threshold was raised from 600 volts (V) to 1,000V in a number of places. Article 490, called “Equipment Over 600 Volts” in 2011, became “Equipment Over 1,000 Volts” in 2014, covering the general requirements for equipment operating at more than 1,000V, nominal. In 2017, the voltage threshold was raised from 600V to 1,000V in more locations throughout the NEC.

Part III in Article 110, now “Over 1,000 Volts, Nominal,” contains sections 110.30 through 110.41. Work space and guarding requirements for conductors and equipment used on circuits over 1,000V, nominal, are in 110.34. In accordance with 110.34(C), the entrance to all buildings, vaults, rooms or enclosures containing exposed live parts or exposed conductors operating at over 1,000V, nominal, shall be kept locked unless such entrances are under the observation of a qualified person at all times. This section continues by stating permanent and conspicuous danger signs shall be provided. The danger sign shall meet the requirements in 110.21(B) and shall read as follows: “DANGER—HIGH ­VOLTAGE—KEEP OUT.”

This requirement is similar to the guarding of live parts requirement for equipment operating at 50 to 1,000V, nominal, in 110.27(A) through (C). Except as elsewhere required or permitted by the NEC, live parts of electrical equipment operating at 50 to 1,000V, nominal, shall be guarded against accidental contact by approved enclosures or by any of the means in 110.27(A)(1) through (4). Both sections require a means to restrict unqualified people from gaining access to energized electrical conductors and circuit parts. Both sections also require conspicuous warning signs forbidding unqualified people to enter. The requirement in 110.34(C) shows exactly what wording shall be on the warning sign: DANGER—HIGH VOLTAGE—KEEP OUT. Although the same wording would be permitted on a door guarding live parts of electrical equipment operating at 50 to 1,000V, nominal, it is not required (see Figure 1).

The locking requirements in 110.34(C) not only pertain to the entrance to all buildings, vaults and rooms containing exposed live parts or exposed conductors operating at over 1,000V, nominal, but they also pertain to the entrance to enclosures. It may be necessary to install the danger sign on the front of the enclosure.

For example, danger signs are on all three doors leading into an electrical room in an industrial facility, but the wording on the signs is AUTHORIZED PERSONNEL ONLY. This electrical room contains a 4,160V switchgear; therefore, a permanent and conspicuous danger sign in accordance with 110.34(C) is required. A sign reading DANGER—HIGH VOLTAGE—KEEP OUT has been permanently attached to the front of the switchgear. Because there are removable access panels on the back of the switchgear, the same danger signs have been installed on each of the removable access panels. All of these danger signs meet the requirement for wording, and they meet the requirements in 110.21(B) for field-applied hazard markings (see Figure 2).

Sections 110.34(C) and 110.27(C) also state the marking on the conspicuous warning signs shall meet the requirements in 110.21(B). In the 2014 edition of the NEC, a new subsection covering field-applied hazard markings was added to 110.21. Besides being in 110.34(C) and 110.27(C), required hazard signs and labels are in numerous places throughout the Code. In accordance with 110.21(B), where the NEC requires caution, warning or danger signs or labels, the labels shall meet all of the requirements in 110.21(B)(1) through (3). Section 110.21(B) only applies to caution, warning and danger signs, not all field or factory labeling.

The first requirement for field-applied hazard markings states the marking shall use effective words, colors or symbols to adequately warn people of the hazard. An informational note under 110.21(B)(1) provides help in determining the physical appearance of the sign or label.

As stated in the informational note, guidelines for suitable font sizes, words, colors, symbols and location requirements for labels are in ANSI Z535.4 2011, Product Safety Signs and Labels. A danger sign indicates a hazardous situation, which, if not avoided, will result in death or serious injury if an accident occurs. This signal word is to be limited to the most extreme situations. A warning sign indicates a hazardous situation, which, if not avoided, could result in death or serious injury if an accident occurs. A caution indicates a hazardous situation, which, if not avoided, could result in minor or moderate injury if an accident occurs (see Figure 3).

The second requirement for field-applied hazard markings states the label shall be permanently affixed to the equipment or wiring method and shall not be hand written. Even if a permanent marker is used, hand writing the words “DANGER,” “WARNING,” or “CAUTION” shall not be permitted.

While using a marker to construct the sign is not permitted, there is certain information that can be written on the sign or label. In accordance with the exception to 110.21(B)(2), portions of labels or markings that are variable, or that could be subject to changes, shall be permitted to be hand written and shall be legible. In accordance with 110.21(B)(3), the label shall be of sufficient durability to withstand the environment involved.

The informational note under this section references an ANSI Standard that provides guidelines for the design and durability of safety signs and labels for application to electrical equipment. The document referenced in this informational note is the same document referenced in the informational note to 110.21(B)(1). While there are a number of locations throughout the Code that require some type of field or factory marking, not every marking has to meet the requirements in 110.21(B).

For example, 110.24(A) pertains to field marking certain equipment with the maximum available fault current. It does say the field markings shall be of sufficient durability to withstand the environment involved but is does not say the marking shall meet the requirements in 110.21(B). Section 110.21(B) only applies to caution, warning and danger signs, such as the danger sign requirement in 110.34(C).
Next month’s column continues the discussion of electrical installation requirements.

About the Author

Charles R. Miller

Code Contributor

Charles R. Miller, owner of Lighthouse Educational Services, teaches classes and seminars on the electrical industry. He is the author of “Illustrated Guide to the National Electrical Code” and NFPA’s “Electrical Reference.” He can be reached at 615...

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