July 1, 2015

H.D. Roberts, Jr.
Corporate Safety Manager
Environmental Management Services, Inc.
12232 Industriplex Blvd., Suite 27
Baton Rouge, LA 70609

Dear Mr. Roberts,

Thank you for your October 29, 2014, correspondence to the Occupational Safety and Health Administration (OSHA), Directorate of Enforcement Programs. You requested information on OSHA requirements related to wiring in cable trays in power generating plants. Your question, and our reply, follow.

Scenario: Many power generating plants have extensive systems of cable trays. Some of the trays are accessible to unqualified workers. For example, sometimes the trays are lower than 8 feet above the work surface and in close proximity to where unqualified workers routinely travel and work. The cable trays carry insulated conductors that operate at a variety of voltages above 50 volts (ac or dc).

Question: What are the OSHA requirements for guarding cable trays that are mounted less than 8 feet above the working surface and accessible to unqualified workers?

Response: If the wiring is part of the utility’s power generating processes or equipment it is covered by 29 CFR 1910.269. Wiring that is not an integral part of, or comingled with, power generating processes or equipment is covered by 29 CFR 1910, Subpart S.^[1] The general rule for both standards is that unqualified employees must not have access to unguarded energized parts.

Under Subpart S, the applicable requirements are found at 29 CFR 1910.303(g)(2), which addresses the guarding of live parts. Paragraph (g)(2)(i) in 29 CFR 1910.303 provides:

Except as elsewhere required or permitted by this standard, live parts of electric equipment operating at 50 volts or more shall be guarded against accidental contact by use of approved cabinets or other forms of approved enclosures or by any of the following means: (A) By location in a room, vault, or similar enclosure that is accessible only to qualified persons; (B) By suitable permanent, substantial partitions or screens so arranged so that only qualified persons will have access to the space within reach of the live parts. . . ; (C) By placement on a suitable balcony, gallery, or platform so elevated and otherwise located as to prevent access by unqualified persons; or (D) By elevation of 2.44 m (8.0 ft) or more above the floor or other working surface.

The conductors in question are “live parts” for purposes of this provision. (“Live parts” are any “[e]nergized conductive components.” See 29 CFR 1910.399.)^[2] And, given that the live parts in the cable trays are not guarded by any of the means described in 29 CFR 1910.303(g)(2)(i)(A) through (g)(2)(i)(D), Subpart S requires them to be guarded against accidental contact by use of approved cabinets or other forms of approved enclosures, except as elsewhere required or permitted by the standard. An enclosure is defined as “[t]he case or housing of apparatus, or the fence or walls surrounding an installation to prevent personnel from accidentally contacting energized parts, or to protect the equipment from physical damage.” See 29 CFR 1910.399. Insulation on a cable is not an enclosure. 

Please note that OSHA will accept wiring methods that meet the National Electrical Code for purposes of compliance with 29 CFR 1910.303(g)(2)(i). Also note that 29 CFR 1910.303(h) contains additional requirements for conductors and equipment used on circuits exceeding 600 volts, nominal, including requirements for enclosures on indoor installations that are accessible to other than qualified persons (see 29 CFR 1910.303(h)(2)(iii)).

In 29 CFR 1910.269, the applicable requirements are found in paragraph (v)(4), which addresses the guarding of rooms and other spaces containing electric supply equipment.^[3] Paragraph (v)(4)(i) in 29 CFR 1910.269 provides:

Rooms and other spaces in which electric supply lines or equipment are installed shall meet the requirements of paragraphs (v)(4)(ii) through (v)(4)(v) . . . [for enclosing and accessing such rooms and spaces] under the following conditions: (A) If exposed live parts operating at 50 to 150 volts to ground are within 2.4 meters (8 feet) of the ground or other working surface inside the room or other space, (B) If live parts operating at 151 to 600 volts to ground and located within 2.4 meters (8 feet) of the ground or other working surface inside the room or other space are guarded only by location as permitted under paragraph (v)(5)(i) . . . [which requires sufficient clearance (horizontal, vertical, or both) to minimize the possibility of accidental employee contact], or (C) If live parts operating at more than 600 volts to ground are within the room or other space, unless (1) The live parts are enclosed within grounded, metal-enclosed equipment whose only openings are designed so that foreign objects inserted in these openings will be deflected from energized parts, or (2) The live parts are installed at a height, above ground and any other working surface, that provides protection at the voltage on the live parts corresponding to the protection provided by a 2.4-meter (8-foot) height at 50 volts.

The conductors in question are “exposed” for purposes of 29 CFR 1910.269, as “exposed” means “[n]ot isolated or guarded.” See 29 CFR 1910.269(x). They are not isolated because they do not require special means for access. “Isolated” means “[n]ot readily accessible to persons unless special means for access are used.” See 29 CFR 1910.269(x).) And they are not “guarded” because they are not “[c]overed, fenced, enclosed, or otherwise protected, by means of suitable covers or casings, barrier rails or screens, mats, or platforms, designed to minimize the possibility, under normal conditions, of dangerous approach or inadvertent contact by persons or objects.” See 29 CFR 1910.269(x). The standard explains that “[w]ires that are insulated, but not otherwise protected, are not guarded.” See 29 CFR 1910.269(x), Note to the definition of “guarded.”

The conductors and cable trays described in your letter are not located in rooms and other spaces that meet the requirements of 29 CFR 1910.269(v)(4)(ii) through (v)(4)(v). Thus, according to the terms of 29 CFR 1910.269(v)(4)(i): if the cables are operating at 50 to 150 volts and installed within 8 feet of the ground or other working surface, they must be isolated or guarded; if the cables are operating at 151 to 600 volts and located within 8 feet of the ground or other working surface, they must be guarded other than by location; and if the cables are operating at more than 600 volts, they must be enclosed within grounded, metal-enclosed equipment whose only openings are designed so that foreign objects inserted in these openings will be deflected from energized parts or installed at an appropriate height more than 8 feet above the working surface. Please note, however, that OSHA will deem wiring methods that meet the requirements of Subpart S (described above) to meet the requirements in 29 CFR 1910.269(v)(4). (See Appendices A-1 and A-2 to 29 CFR 1910.269.)

Thank you for your interest in occupational safety and health. We hope you find this information helpful. 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. If you have any further questions, please feel free to contact the Directorate of Enforcement Programs at (202) 693-2100.

Sincerely,

Thomas Galassi, Director
Directorate of Enforcement Programs

^[1] See Note 3 to 29 CFR 1910.331(c)(1) for information about the extent to which the wiring must be commingled.

^[2] Your letter correctly states that Note 2 in Table S-1 in Subpart S provides that “[i]nsulated wire or insulated busbars operating at not over 300 volts are not considered live parts.” However, OSHA has previously clarified that that note applies only to the working clearance provisions contained in 29 CFR 1910.303(g)(1); it does not apply generally to the use of that term elsewhere in the standard, including the provisions for guarding live parts in 29 CFR 1910.303(g)(2). See https://www.osha.gov/laws-regs/standardinterpretations/2005-07-01.

^[3] Paragraph (v)(5) of 29 CFR 1910.269 generally requires employers to provide guards around live parts operating at more than 150 volts to ground without an insulating covering.  This provision does not apply to the insulated cables described in your letter.