Electrical Safety: General Requirements and Wiring Methods

Shocks, burns, and electrical fires can start with ordinary things: a missing box cover, a blocked panel, a misused extension cord. These two sections require you to use approved equipment, keep it intact and marked, keep the space around it clear, guard live parts, and limit temporary wiring and flexible cords to the uses the rules allow.

Who it applies to

Sections 1910.302 through 1910.308 cover electrical installations and utilization equipment installed or used within or on buildings, structures, and other premises, including yards and industrial substations (1910.302(a)(1)).

They do not cover installations in ships, watercraft, railway rolling stock, aircraft, or automotive vehicles other than mobile homes and recreational vehicles, installations underground in mines, or certain railway and utility installations (1910.302(a)(2)).

The age of the installation matters:

• Of the paragraphs in this guide, these apply regardless of when the installation was designed or installed: 1910.303(b), (e), (f) except (f)(4) and (f)(5), and (g)(2), plus 1910.305(g)(1), (g)(2)(ii), and (g)(2)(iii) (1910.302(b)(1)).
• Installations and equipment installed or overhauled after March 15, 1972, must comply with all of 1910.302 through 1910.308, except as noted in 1910.302(b)(3) and (b)(4) (1910.302(b)(2)). The approval, working space, temporary wiring, and box cover rules below fall here, not on the all-installations list.

What the standard requires

Use approved equipment as listed

• Conductors and equipment are acceptable only if approved, as defined in 1910.399 (1910.303(a)). Approved means acceptable to OSHA, and one route to acceptable is equipment accepted, certified, listed, labeled, or otherwise determined to be safe by a nationally recognized testing laboratory (1910.399).
• Electric equipment must be free from recognized hazards that are likely to cause death or serious physical harm to employees (1910.303(b)(1)).
• Listed or labeled equipment must be installed and used in accordance with any instructions included in the listing or labeling (1910.303(b)(2)).

Keep equipment intact and closed up

• Unused openings in boxes, raceways, auxiliary gutters, cabinets, equipment cases, or housings must be effectively closed to give protection substantially equivalent to the wall of the equipment (1910.303(b)(7)(i)). Unused openings in cabinets, boxes, and fittings must be effectively closed (1910.305(b)(1)(ii)).
• There must be no damaged parts that may adversely affect safe operation or mechanical strength of the equipment (1910.303(b)(7)(iv)).
• All pull boxes, junction boxes, and fittings must have covers identified for the purpose. Metal covers must be grounded. In completed installations, each outlet box must have a cover, faceplate, or fixture canopy (1910.305(b)(2)(i)).

Mark equipment, disconnects, and circuits

• Equipment may not be used unless it is marked with the manufacturer's name, trademark, or other descriptive marking, and with voltage, current, wattage, or other ratings as necessary (1910.303(e)(1)).
• Each required disconnecting means for motors and appliances, and each service, feeder, and branch circuit at its disconnecting means or overcurrent device, must be legibly marked to indicate its purpose, unless located and arranged so the purpose is evident (1910.303(f)(1), (f)(2)).
• Required disconnecting means must be capable of being locked in the open position (1910.303(f)(4)). This applies only to installations and equipment installed after August 13, 2007 (1910.302(b)(4)).

Keep working space clear (600 volts or less)

Sufficient access and working space must be provided and maintained about all electric equipment (1910.303(g)(1)). For equipment likely to require examination, adjustment, servicing, or maintenance while energized, except as required or permitted elsewhere in the subpart (1910.303(g)(1)(i)):

• Depth may not be less than Table S-1 (1910.303(g)(1)(i)(A)). At 0 to 150 volts to ground, that is 0.9 m (3.0 ft). At 151 to 600 volts to ground, it is 0.9 m (3.0 ft), 1.0 m (3.5 ft), or 1.2 m (4.0 ft) under Conditions A, B, and C, defined in Note 2 to the table. Note 1 allows 0.7 m (2.5 ft) for installations built before April 16, 1981.
• Width must be the width of the equipment or 762 mm (30 in.), whichever is greater, and doors or hinged panels must be able to open at least 90 degrees (1910.303(g)(1)(i)(B)).

Working space required by the standard may not be used for storage (1910.303(g)(1)(ii)).

Guard live parts

Except as elsewhere required or permitted by the standard, live parts of electric equipment operating at 50 volts or more must be guarded against accidental contact by approved cabinets or other approved enclosures, or by one of these means (1910.303(g)(2)(i)):

• Location in a room, vault, or similar enclosure accessible only to qualified persons
• Suitable permanent, substantial partitions or screens arranged so that only qualified persons have access to the space within reach of the live parts
• Placement on a suitable balcony, gallery, or platform elevated and located to prevent access by unqualified persons
• Elevation of 2.44 m (8.0 ft) or more above the floor or other working surface

Entrances to rooms and other guarded locations containing exposed live parts must be marked with conspicuous warning signs forbidding unqualified persons to enter (1910.303(g)(2)(iii)).

Limit temporary wiring

Temporary power and lighting installations of 600 volts, nominal, or less may be used only (1910.305(a)(2)(i)):

• During and for remodeling, maintenance, or repair of buildings, structures, or equipment, and similar activities
• For a period not to exceed 90 days for Christmas decorative lighting, carnivals, and similar purposes
• For experimental or development work, and during emergencies

Temporary wiring must be removed immediately upon completion of the project or purpose for which it was installed (1910.305(a)(2)(ii)).

Use flexible cords only where allowed

Flexible cords and cables must be approved for conditions of use and location (1910.305(g)(1)(i)). They may be used only for (1910.305(g)(1)(ii)):

• Pendants, wiring of fixtures, and connection of portable lamps or appliances
• Portable and mobile signs, elevator cables, and wiring of cranes and hoists
• Connection of stationary equipment to facilitate frequent interchange
• Prevention of the transmission of noise or vibration
• Appliances where the fastening means and mechanical connections are designed to permit removal for maintenance and repair
• Data processing cables approved as part of the data processing system
• Connection of moving parts
• Temporary wiring as permitted in 1910.305(a)(2)

Unless specifically permitted otherwise in that list, they may not be used (1910.305(g)(1)(iv)):

• As a substitute for the fixed wiring of a structure
• Where run through holes in walls, ceilings, or floors
• Where run through doorways, windows, or similar openings
• Where attached to building surfaces
• Where concealed behind building walls, ceilings, or floors
• Where installed in raceways, except as otherwise permitted in the subpart

Flexible cords may be used only in continuous lengths without splice or tap. The exception: hard-service and junior hard-service cord No. 14 and larger may be repaired if the splice retains the insulation, outer sheath properties, and usage characteristics of the cord (1910.305(g)(2)(ii)). Cords must be connected so that strain relief prevents pull from being directly transmitted to joints or terminal screws (1910.305(g)(2)(iii)). A conductor used as a grounded or equipment grounding conductor must be distinguishable from other conductors (1910.305(g)(2)(i)).

Training

Training is in a separate section, 1910.332. It applies to employees who face a risk of electric shock that is not reduced to a safe level by the installation requirements of 1910.303 through 1910.308 (1910.332(a)). They must be trained in the safety-related work practices required by 1910.331 through 1910.335 that pertain to their job assignments (1910.332(b)(1)). Section 1910.332 does not set a retraining interval.

Written programs and records

The paragraphs covered here do not call for a written program or set a retention period. They require markings instead, on equipment, disconnects, and circuits. Those markings must be durable enough to withstand the environment involved (1910.303(e)(2), (f)(3)).

Easy-to-miss requirements

• Internal parts of electrical equipment, including busbars, wiring terminals, and insulators, may not be damaged or contaminated by foreign materials such as paint, plaster, cleaners, abrasives, or corrosive residues (1910.303(b)(7)(iii)).
• When normally enclosed live parts are exposed for inspection or servicing, the working space, if in a passageway or general open space, must be suitably guarded (1910.303(g)(1)(ii)).
• A flexible cord used for the portable lamp or appliance, stationary equipment, or removable appliance uses listed above must have an attachment plug and be energized from an approved receptacle outlet (1910.305(g)(1)(iii)).

Related guides

• Lockout/tagout
• PPE hazard assessment

Source

This guide is based on the text of 29 CFR 1910.303 and 29 CFR 1910.305, with 1910.302 (scope), 1910.332 (training), and 1910.399 (definitions), as published on osha.gov. The regulation itself always controls. States that run their own OSHA-approved State Plans may have additional or stricter rules.