General electrical requirements

Electrical equipment must be approved, meaning it has been judged safe for its intended use by a nationally recognized testing laboratory or other accepted certification method. Employers must ensure equipment is suitable for the installation and use and that suitability may be shown by listing, labeling, or certification for the identified purpose (see 1926.403(a) and 1926.403(b)(1)(i).

• If equipment is listed or labeled for a specific use, install and use it according to the manufacturer's listing and instructions (1926.403(b)(2)).

The employer is responsible for ensuring electrical equipment is free from recognized hazards likely to cause death or serious physical harm to employees. The standard places the duty on the employer to examine equipment for suitability, mechanical strength, insulation, heating and arcing effects, and other factors that affect employee safety (1926.403(b)(1)).

• Document inspection and maintenance practices as part of your safety program to show compliance with this employer obligation.

Listed, labeled, or certified equipment must be installed and used in accordance with the instructions included in the listing, labeling, or certification. Do not change or substitute installation methods that contradict the listing or manufacturer's instructions (1926.403(b)(2)).

• Keep manufacturer's installation instructions available for reference during installation and inspections.

An interrupting rating is the maximum current that a device (like a circuit breaker) can safely interrupt at the system voltage, and equipment intended to break current must have an interrupting rating sufficient for the current that may need to be interrupted. Ensure overcurrent devices and switches are rated to handle possible fault currents at system voltage (1926.403(c)).

• If you cannot verify the interrupting rating from the equipment markings or documentation, consult the manufacturer or a qualified electrical engineer before placing the equipment in service.

No; wooden plugs driven into holes in masonry, concrete, plaster, or similar materials shall not be used to mount electrical equipment. Electrical equipment must be firmly secured to its mounting surface by suitable fasteners (1926.403(d)(1)).

• Use anchors and fasteners rated for the weight and vibration expected for the equipment and appropriate for the substrate.

Equipment that cools by natural air circulation must be installed so air flow over exposed surfaces is not blocked, and conductors must be spliced with devices designed for their use or by proper brazing/welding or soldering, with splices insulated equivalent to the conductor. Provide clearances above and around floor-mounted equipment to dissipate rising warm air and make sure all splices are mechanically secure and insulated (1926.403(d)(2) and 1926.403(e)).

• Soldered splices must be mechanically secure before soldering and then insulated with equivalent insulation or an insulating device.

Parts of electrical equipment that normally produce arcs, sparks, flames, or molten metal must be enclosed, separated, or isolated from all combustible material. Do not allow arcing parts to be adjacent to combustible dusts, paper, wood, or insulation that could ignite (1926.403(f)).

• Use barriers, noncombustible enclosures, or maintain sufficient separation distances when enclosing is not feasible.

Electrical equipment must bear the manufacturer's name, trademark, or other identifying marking and necessary ratings (voltage, current, wattage), and disconnecting means for motors and appliances must be legibly marked to indicate their purpose unless the purpose is obvious by location. Markings must be durable for the environment involved (1926.403(g) and 1926.403(h)).

• Regularly inspect markings and replace or re-mark equipment where identification has faded or been damaged.

The minimum working clearance in the direction of access for equipment operating 151–600 volts to ground is 3 feet for Condition (a), 3.5 feet for Condition (b), and 4 feet for Condition (c) as shown in Table K-1. Measure distances from exposed live parts or the enclosure front/opening (1926.403(i)(1)(i)).

• Determine which condition applies: (a) no grounded parts on the other side, (b) grounded parts on the other side, or (c) live parts on both sides with operator between.

Working space in front of electric equipment must be at least 30 inches (762 mm) wide. Distances are measured from the live parts if exposed or from the enclosure front or opening if live parts are enclosed (1926.403(i)(1)(ii)).

• Walls of concrete, brick, or tile are considered grounded and affect the condition used to determine clearance depth in Table K-1.

You must provide at least one entrance to the working space, a minimum front working space of 3 feet where live parts are normally exposed on the front, and a minimum headroom of 6 feet 3 inches (1.91 m) in the working space around service equipment, switchboards, panelboards, or motor control centers (1926.403(i)(1)(iii)–(v)).

• If live parts are exposed, guard the working space in passageways or open spaces during inspection or servicing.

No; working space required by this subpart shall not be used for storage. Keep the area clear so personnel can safely operate and maintain energized or de-energized equipment (1926.403(i)(1)).

• Post signs or enforce housekeeping procedures to prevent tools, materials, or debris from occupying required clearances.

Live parts operating at 50 volts or more must be guarded against accidental contact by cabinets or enclosures or by one of the permitted means such as location in a room accessible only to qualified persons, partitions or screens, location on an elevated balcony/platform, or by elevation of 8 feet or more to exclude unqualified persons (1926.403(i)(2) and 1926.403(i)(2)(i)).

• Where guards are used, openings in partitions or screens must be sized and placed so accidental contact or insertion of conducting objects is unlikely.

Where electric equipment would be exposed to physical damage, enclosures or guards must be strong enough to prevent such damage, and entrances to guarded locations with exposed live parts must display conspicuous warning signs forbidding unqualified persons to enter (1926.403(i)(2)(ii)–(iii)).

• Use lockable access control, barriers, or elevated platforms and post clear signage to prevent unqualified access.

For equipment over 600 volts, applicable provisions (a) through (g) still apply and are supplemented by additional requirements: enclosed installations for unqualified access, larger minimum clearances and headroom, and specific depth requirements in Table K-2 for working space based on voltage and conditions (1926.403(j)(1)–(3)).

• Refer to Table K-2 to determine minimum depth (for example, 3–5 feet or greater depending on voltage and condition) and ensure workspace allows a 90° door/panel opening (1926.403(j)(3)(i)).

If installations are accessible to unqualified persons, they must be made with metal-enclosed equipment or be enclosed in a vault or area with access controlled by a lock, and metal-enclosed equipment must be marked with appropriate caution signs; guards must be provided where equipment is exposed to vehicular traffic (1926.403(j)(2)(ii)).

• Keep doors locked or otherwise control access to rooms/enclosures containing exposed live parts over 600 volts as required by 1926.403(j)(2).

For nominal voltages 2,501 to 9,000 volts to ground, Table K-2 requires minimum clear depths of 4 feet for Condition (a), 5 feet for Condition (b), and 6 feet for Condition (c); select the condition based on whether grounded parts are opposite the live parts or live parts are on both sides (1926.403(j)(3)(i)).

• Measure from exposed live parts or the enclosure front and ensure depth allows a full 90° door/panel opening (1926.403(j)(3)).

Lighting outlets must be arranged so that persons changing lamps or making repairs will not be endangered by live parts or other equipment, and points of control must be located so operators are not likely to contact live or moving parts while operating equipment (1926.403(j)(3)(ii)–(iii)).

• Position lighting and control points to allow safe maintenance and operation without exposing workers to energized parts.

At least one entrance not less than 24 inches (610 mm) wide and 6 feet 6 inches (1.98 m) high must be provided to give access to working space around electric equipment, and on switchboards/control panels over 48 inches wide, provide an entrance at each end where practicable (1926.403(j)(4)).

• Ensure any bare energized parts or insulated energized parts above 600 volts near entrances are guarded to prevent accidental contact.

Ventilating or similar openings in metal-enclosed equipment must be designed so that foreign objects inserted through these openings will be deflected from energized parts, preventing accidental contact or shorts (1926.403(j)(3)).

• Use screens, baffles, or louvers sized and placed to prevent tools, debris, or fingers from reaching energized components.

Yes; live parts can be guarded by locating them in a room, vault, or similar enclosure that is accessible only to qualified persons, and entrances to such guarded locations must be marked with conspicuous warning signs forbidding unqualified persons to enter (1926.403(i)(2)(i)(A) and 1926.403(i)(2)(iii)).

• Use locks, access controls, and training to ensure only qualified persons enter these areas; post clear warning signage at entrances.

Soldered splices must first be made so they are mechanically and electrically secure without solder, and then soldered, with all splices and free conductor ends covered with insulation equivalent to the conductors or an insulating device designed for the purpose (1926.403(e)).

• Inspect splices for mechanical integrity before soldering and use heat-shrink tubing or equivalent insulating devices rated for the conductor.