The National Electric Safety Code (NESC) is the primary standard that governs our work practices.

The standards are revised on a 5-year schedule, with the 2017 revision just released in August.

After reading through the revisions, I found the identification changes to be relatively minor; generally revised to add detail and clarity.

Yet there are some important distinctions to draw from certain word changes and additions.

Provided below, is the list of changes I have documented between the 2017 and previous 2012 revisions.

Because of the obvious nature of Electromark’s business being safety signs, labels, tags, and asset identification for the utility industry, I have focused solely on those paragraphs that relate to safety and identification marking requirements within the NESC.

The changes noted here are identified by general area of application followed by the relevant paragraph number within the standard.


No Specific Paragraph Ref – All references to ANSI Z535 have been updated to reference the most current (2011) revision of that standard.

Substation Sign Requirements – 110.A.1.c

Substation Entrance

 This paragraph is expanded in the 2017 rev. to provide greater detail and clarity.

The 2012 rev. simply states; “A safety sign shall be displayed at each entrance. For fenced electric supply stations, a safety sign shall be displayed on each side of the fenced enclosure.”

The 2017 rev. clarifies the placement location by stating “beside the door or gate at each entrance.”

Substations w. Fence Enclosures

The 2017 rev. also distinguishes between enclosures without roofs (i.e. a simple fenced enclosure), and those entirely enclosed by having a roof (i.e. a brick or metal sided building enclosure).

For simple fence enclosures, the requirement remains essentially the same as stated in the 2012 rev.; a safety sign on each exterior side of the enclosure.

Note, however, that the word “exterior” was absent from the 2012 revision.

This clarifies which side of the fence the signs are to be attached; presumably and logically to prevent the fence from obscuring or making the sign message less readable.

Fully Enclosed Substations

The 2017 rev. also includes the requirements, not in the 2012 rev. that where the station is entirely enclosed by a roof, a safety sign is only required at all ground level entrances.

Where entrance to roofed enclosures may be gained through sequential doors, the safety sign should be located on the inner door position.

Fire Extinguisher Equipment

114 –  In the previous 2012 NESC this paragraph required all fire extinguishing equipment located in and for use in electrical supply stations be conspicuously marked.

This rule further noted the exception that it did not apply to unmanned, outdoor substations that do not contain a control or similar building and that the rule was not intended to require fire extinguishers or systems in all supply stations or areas of larger more complex stations.

This rule is omitted from the 2017 edition.

Switchgear and Metal-Enclosed Bus in Electrical Supply Stations

180.B.11  – The 2017 rev. states: “For metal-enclosed power switchgear an ANSI safety sign shall be placed in each cubical containing more than one voltage source greater than 1000v.” The 2012 rev. was less specific, “more than one high-voltage source”.

Readily Climbable Structures

217.A.2.a – This rule requires readily climbable structures carrying supply conductors adjacent to roads of areas where people may regularly travel or gather to be equipped with barriers or posted with appropriate ANSI safety signs.

The 2012 rev. used the wording “barriers to inhibit climbing by unqualified persons”. This was replaced with “unauthorized persons” in the 2017 rev.

Overhead Lines

220.C.2.B.3 –  The 2012 rev. provided a conditional requirement option that required different circuits grouped together but owned by separate utilities to have ownership and voltage prominently displayed.

This was included as one of three option requirements.

This conditional option is not included in the 2017 rev., and the other two option requirements in the 2012 rev. are combined as a single requirement in the 2017 rev.

Padmount Transformers/ Above Ground Equipment

381.G.2 – Equipment/Design. In the 2017 rev. this requirement states that an ANSI safety sign should be visible when the first door/barrier of a padmount transformer or above-ground equipment is removed.

The 2012 rev. provided this specification as a recommendation.

While very close in meaning, under the paragraph 015. Intent on pg. 5 of the 2017 rev. these words have subtly different meanings in terms of specified practice that suggests ‘should’ as signifying a stronger directive than ‘recommendation’.

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