OSHA requirements are set by statute, standards and regulations. Our interpretation letters explain these requirements and how they apply to particular circumstances, but they cannot create additional employer obligations. This letter constitutes OSHA's interpretation of the requirements discussed. Note that our enforcement guidance may be affected by changes to OSHA rules. Also, from time to time we update our guidance in response to new information. To keep apprised of such developments, you can consult OSHA's website at https://www.osha.gov.

December 18, 1997

			Assistant Regional Administrator
			Technical Support - Region V

FROM:			JOHN B. MILES, JR., Director
			Directorate of Compliance Programs

SUBJECT:		Electrical Conductor Identification

This is in response to your September 12 memorandum to which you attached a telefaxed copy of an August 28 letter with enclosures from J. B. Faber of Sargent & Lundy, 55 E. Monroe Street, Chicago, IL 60603 to Sheila Hall, OSHA, 230 S. Dearborn Street, Chicago, IL 60604. In your memorandum, you requested replies to the following questions posed in consideration of the information provided in the enclosures to the aforementioned August 28 letter.

Question 1:

Are building services such as heating, ventilation, and air conditioning (HVAC), and lighting for a power plant included as part of the exception listed in paragraph 1910.302(a)(2)(v) for installations under the exclusive control of utilities? If yes, what standard, if any, would be applicable for the wiring at these facilities since sections 1910.302 - 1910.308 would not apply


No. The heating, ventilation, air conditioning (HVAC), and lighting circuits are almost never wired as an integral part of the electric power generation installation and would therefore almost always be covered by Subpart S.


With respect to 29 CFR 1910 Subpart S, the Occupational Safety and Health Administration (OSHA) considers the covered installation to begin where it becomes electrically independent of conductors and equipment used for the generation of electric power. This is further clarified on page 31991 of the preamble to the Electrical Safety-Related Work Practices Final Rule published in Volume 55, Number 151 of the Federal Register on Monday, August 6, 1990.

Question 2:

If the answer to Question 1 above would require that a conductor in these applications, use a grounded conductor or an equipment grounding conductor, be identified and distinguishable from all other conductors, would the use of a diagram meet this requirement? If it would not, can you provide any suggestions for identifying equipment already in use? Diagrams are included as part of the request to show the complexity of the application.


The use of a diagram would not be an acceptable form of identifying and distinguishing grounded circuit conductors and equipment grounding circuits. Under paragraph 1910.304(a), a conductor used as a grounded circuit conductor and a conductor used as an equipment grounding conductor must be identifiable and distinguishable from all other conductors. An employee must be able to distinguish an equipment grounding conductor from any other type of conductor in a plant. Likewise, an employee must be able to distinguish a grounded circuit conductor from any other type of conductor in a plant. Neither of these conductors may be of the same color as any other type of conductor.


If a wiring diagram were the only means of identifying these conductors, an employee (to perform work safely) would have to look up the color coding on the each time there is a need to distinguish or identify circuit or equipment conductors each time there is need to identify circuit or equipment conductors. For example, the wiring diagram attached to Mr. Faber's fax appears to indicate that a red conductor is used as a grounding conductor. (This is not entirely clear on the diagram.) The use of this color makes it much more likely that an employee would confuse a red ungrounded circuit conductor with an equipment grounding conductor in a similar panel. Such a mistake could lead to an employee being exposed to hazardous electrical energy. Of particular concern are employees of electrical contractors, who are familiar with standard color coding schemes, making this mistake.


The source national consensus standard for 29 CFR 1910 Subpart S-Electrical is National Fire Protection Association NFPA 70-88 National Electrical Code (NEC). As noted in Appendix A of Subpart S, the NEC is listed as a reference intended for use in understanding the requirements contained in Subpart S. The National Electrical Code (NFPA 70) contains requirements that employers can follow to comply with the OSHA requirements to identify conductors. It also provides acceptable guidelines for identifying conductors at their terminations (See section 200-6).


In your memorandum you disclosed that the clarification you requested is on electrical conductors and equipment involving Sargent & Lundy, an international company. Under paragraph 1910.303(a), workplace electrical conductors and equipment must be approved to be acceptable to OSHA. Under the paragraph 1910.399 definition of "acceptable," an electrical conductor or equipment is acceptable to OSHA and approved within the meaning of 29 CFR 1910 Subpart S-Electrical if it is accepted, or certified, or listed, or labeled, or otherwise determined to be safe by a nationally recognized testing laboratory (NRTL) or otherwise stipulated under the definition of "acceptable."

Question 3:

Would OSHA consider owners of a generating station to be classified as a utility even if they were not necessarily chartered as a utility?


As discussed in the preamble (on page 4039) to the Subpart S-Electrical Standard Final Rule (published in Volume 46, Number 11 on Friday, January 16, 1981), electric power generation installations that are similar to those of an electric utility are treated as electric utility installations whether or not they are actually under the control of utility.


This is clarified further in the preamble (on pages 4333 and 4334) to the Electric Power Generation Standard Final Rule, published in the Federal Register, Volume 59, Number 20, on Monday, January 31, 1994. A generating station may be covered by §1910.269 regardless of whether it is owned by a chartered utility company. By the Note following paragraph 1910.269(a)(1)(i)(A), §1910.269 covers generation, transmission, and distribution installations of electric utilities, as well as, equivalent installations of industrial establishments.