Wiring methods and requirements

No — the wiring method rules in 1926.405(a) do not apply to conductors that form an integral part of equipment such as motors, controllers, motor control centers, and similar equipment. Employers should treat those conductors as part of the equipment rather than as separate wiring under 1926.405(a).

Metal raceways, cable armor, and other metal enclosures must be metallically joined into a continuous conductor and be connected to boxes, fittings, and cabinets to provide effective electrical continuity. This means all metal parts that serve as raceway or enclosure must be bonded so they form a continuous grounding/return path as required by 1926.405(a)(1)(i).

No — no wiring systems of any type may be installed in ducts used to transport dust, loose stock, flammable vapors, or in ducts used for vapor removal or in shafts containing only such ducts. Installing wiring in those ducts is prohibited by 1926.405(a)(1)(ii).

Temporary wiring must comply with the temporary-wiring provisions and be removed immediately when construction or the purpose for which it was installed is complete. Paragraph 1926.405(a)(2)(i) states that temporary power and lighting may be of a class less than permanent installations but otherwise must meet the subpart's permanent-wiring requirements unless specifically modified, and temporary wiring shall be removed immediately upon completion.

Temporary feeders must originate in a distribution center and may be run as multiconductor cord or cable assemblies, within raceways, or as open conductors on insulators (not more than 10 feet apart) where they are not subject to physical damage. These routing and origin requirements are in 1926.405(a)(2)(ii)(A).

Temporary branch circuits must originate in a power outlet or panelboard and may be run as multiconductor cord/cable assemblies, open conductors, or in raceways, and all conductors must be protected by overcurrent devices sized to their ampacity. See 1926.405(a)(2)(ii)(B).

Runs of open conductors must be located where they will not be subject to physical damage and must be fastened at intervals not exceeding 10 feet (3.05 m). Also, branch-circuit conductors must not be laid on the floor. These rules are in 1926.405(a)(2)(ii).

Temporary branch circuits that supply receptacles or fixed equipment must contain a separate equipment grounding conductor if run as open conductors, and all receptacles must be of the grounding type and electrically connected to the grounding conductor unless the branch circuit is installed in a complete metallic raceway. Also, receptacles for non-lighting uses shall not be on branch circuits supplying temporary lighting. See 1926.405(a)(2)(ii)(C).

Temporary circuits must have disconnecting switches or plug connectors installed so that all ungrounded conductors of each temporary circuit can be disconnected. This requirement is stated in 1926.405(a)(2)(ii)(D).

All lamps used for general illumination must be protected from accidental contact or breakage, and metal-case sockets must be grounded. These protections are required by 1926.405(a)(2)(ii)(E).

No — temporary lights must not be suspended by their electric cords unless both the cords and lights are specifically designed for suspension by the cord. This prohibition is found in 1926.405(a)(2)(ii)(F).

Portable electric lighting used in wet or other conductive locations must operate at 12 volts or less, but 120-volt lights may be used only if protected by a ground-fault circuit interrupter (GFCI). See 1926.405(a)(2)(ii)(G).

A box must be used wherever a change is made to a raceway system or a cable system that is metal-clad or metal-sheathed. This requirement is in 1926.405(a)(2)(ii)(H).

Flexible cords and cables must be protected from damage; sharp corners and projections must be avoided, and cords may pass through doorways or similar openings only if protection is provided to prevent damage. See 1926.405(a)(2)(ii)(I).

Extension cord sets used with portable electric tools and appliances must be three‑wire type and designed for hard or extra‑hard usage; flexible cords for temporary and portable lights must also be designed for hard or extra‑hard usage. See 1926.405(a)(2)(ii)(J).

For temporary wiring over 600 volts nominal, employers must provide fencing, barriers, or other effective means to prevent access by anyone other than authorized and qualified personnel. See 1926.405(a)(2)(iii).

Conductors entering boxes, cabinets, or fittings must be protected from abrasion, and openings through which conductors enter must be effectively closed; unused openings must also be effectively closed. This protection requirement is in 1926.405(b)(1).

All pull boxes, junction boxes, and fittings must have covers; if metal covers are used they must be grounded. In energized installations each outlet box must have a cover, faceplate, or fixture canopy, and covers with holes for flexible cord pendants must have bushings or smooth, well-rounded surfaces for the cords. See 1926.405(b)(2).

Pull and junction boxes for systems over 600 volts must provide a complete enclosure for the conductors and be closed by securely fastened covers; covers must be permanently marked "HIGH VOLTAGE" on the outside and be readily visible and legible. See 1926.405(b)(3)(i) and 1926.405(b)(3)(ii).

Knife switches must be connected so blades are dead when the switch is open and be located so gravity will not tend to close them; switchboards with exposed live parts must be in permanently dry locations and accessible only to qualified persons, and panelboards must be mounted in cabinets, cutout boxes, or enclosures and be dead front unless accessible only to qualified persons. See 1926.405(c) and 1926.405(d).

Enclosures (cabinets, boxes, fittings, panelboard enclosures) in damp or wet locations must be installed to prevent moisture or water from entering and accumulating; in wet locations enclosures must be weatherproof, and switches and circuit breakers in wet locations must be enclosed in weatherproof enclosures. See 1926.405(e)(1) and 1926.405(e)(2).

All conductors for general wiring must be insulated (unless otherwise permitted) with insulation suitable for the voltage, operating temperature, and location, and insulated conductors must be distinguishable by color or other means to identify grounded, ungrounded, or equipment grounding conductors. See 1926.405(f).

Flexible cords and cables are permitted only for specific uses such as pendants, wiring of fixtures, connection of portable lamps or appliances, elevator cables, wiring of cranes and hoists, connection of stationary equipment to permit frequent interchange, preventing transmission of noise or vibration, and appliances designed for removal for maintenance and repair. These permitted uses are listed in 1926.405(g)(1)(i).

If flexible cords are used for connection of portable lamps/appliances, connecting stationary equipment for interchange, or appliances designed for removal, they must be equipped with attachment plugs and energized from receptacle outlets per 1926.405(g)(1)(ii). Flexible cords are prohibited as a substitute for fixed wiring; where run through holes in walls, ceilings, or floors; where run through doorways/windows except as allowed by 1926.405(a)(2)(ii)(I); where attached to building surfaces; or where concealed behind building walls, ceilings, or floors, per 1926.405(g)(1)(iii).

Cords of type SJ, SJO, SJT, SJTO, S, SO, ST, and STO must be durably marked with the type designation, size, and number of conductors; flexible cords generally must be used in continuous lengths without splice or tap, though hard service flexible cords No. 12 or larger may be repaired with a splice that preserves the cord's insulation and outer-sheath properties. See 1926.405(g)(2)(ii) and 1926.405(g)(2)(iii).

Flexible cords must be connected to devices and fittings with strain relief to prevent pull from being transmitted to joints or terminal screws, and flexible cords passing through holes in covers, outlet boxes, or similar enclosures must be protected by bushings or fittings. See 1926.405(g)(2)(iv) and 1926.405(g)(2)(v).

Multiconductor portable cable supplying power to portable or mobile equipment over 600 volts nominal must use No. 8 or larger conductors with flexible stranding, and cables operated over 2000 volts must be shielded to confine voltage stresses to the insulation. See 1926.405(h).

Fixture wires may be used only inside lighting fixtures (or similar enclosed equipment) and to connect fixtures to branch-circuit conductors, and they may not be used as branch-circuit conductors except for Class 1 power-limited circuits. See Uses permitted in 1926.405(i)(2) and Uses not permitted in 1926.405(i)(3).

• Practical point: use fixture wire only where it will be enclosed or protected and not subject to bending or twisting, and do not run it as a general-purpose branch circuit conductor unless it is for a permitted Class 1 power-limited circuit.

A fixture wire used as a grounded conductor must be suitable for the voltage, temperature, and location of use and must be identified as the grounded conductor. See the General requirements in 1926.405(i)(1).

• Practical point: mark or color the conductor appropriately (for example, the standard grounded conductor identification) and ensure the wire type is rated for the fixture’s environment and temperature.

Portable handlamps must be wired with flexible cord and a polarized or grounding attachment plug, have an insulating handle, a substantial guard, and must not use metal-shell, paper-lined lampholders. See Portable lamp requirements in 1926.405(j)(1)(iii) and the related provisions 1926.405(j)(1)(iii)(A)–(D).

• Practical checklist: flexible cord with correct plug type; molded or other insulating handle; guard attached to lampholder or handle; no metal shell paper-lined lampholders.

Yes — metallic guards on handlamps must be grounded by an equipment grounding conductor run inside the power supply cord. See 1926.405(j)(1)(iii)(D).

• Practical point: use a three-conductor cord with the grounding conductor connected to the guard and to the equipment grounding terminal of the plug so the guard is bonded to equipment ground.

Fixtures, lampholders, rosettes, and receptacles must be securely supported, and screw-shell lampholders used in wet or damp locations must be of the weatherproof type; fixtures installed in wet or damp locations must be identified for that use and installed so water cannot enter or accumulate in electrical parts. See Support and general requirements in 1926.405(j)(1)(ii), Lampholders in 1926.405(j)(1)(iv), and Fixtures in 1926.405(j)(1)(v).

• Practical tips: don’t support heavy fixtures by a lampholder screw shell; select fixtures and lampholders listed for wet/damp locations; make sure housings and wireways shed water and remain dry.

Receptacles, cord connectors, and plugs must be constructed so they won’t accept a plug rated for a different voltage or current than the device is intended for, and receptacles installed in wet or damp locations must be designed for that location. See Configuration rules in 1926.405(j)(2)(i) and Damp/wet location requirement in 1926.405(j)(2)(ii).

• Practical point: use properly keyed or non-interchangeable plugs/receptacles for different voltages; in wet areas use weatherproof or gasketed devices and covers rated for the environment.

The disconnecting means must disconnect the motor and controller from all ungrounded supply conductors, be designed so no pole can be operated independently, be located in sight from the controller (unless otherwise permitted with proper marking), plainly indicate ON/OFF position, and be readily accessible. See Disconnecting means requirements in 1926.405(j)(4)(ii).

• Practical points: install disconnects that clearly show open/closed; place them within 50 feet and visible from the controller unless the exception for over-600 V controllers applies with marking and lockout provisions.

A single disconnecting means may serve a group of motors if they drive parts of a single machine, are protected by one set of branch-circuit protective devices, or are in a single room in sight from the disconnect location. See Conditions in 1926.405(j)(4)(ii)(F)(1)–(3).

• Practical example: multiple motors on one machine (e.g., a multi-spindle woodworking machine) can use one disconnect; separate independent motors in different areas generally need individual disconnects.

Motors, motor-control apparatus, and motor branch-circuit conductors must be protected against overheating from overloads or failure to start, and against short-circuits and ground faults, except where overload protection would create a greater hazard (for example, fire pumps). See Motor protection requirements in 1926.405(j)(4)(iii).

• Practical note: ensure proper overcurrent devices, overload relays, and ground-fault protection are installed unless a documented safety exception applies.

Exposed live parts of motors and controllers operating at 50 volts or more between terminals must be guarded against accidental contact unless they are placed where access is restricted to qualified persons (in a room or enclosure), elevated on a balcony or platform to exclude unqualified persons, or elevated 8 feet or more above the floor. See Guarding and permitted alternatives in 1926.405(j)(4)(iv)(A)(1)–(3).

• Practical application: if regular attendance or adjustment is needed during operation and the only guard is location-based, provide insulating mats or platforms per 1926.405(j)(4)(iv)(B).

Transformers over 35 kV installed indoors must be placed in a vault, and oil-insulated transformers that present a fire hazard indoors must also be in a vault; operating voltages of exposed live parts must be visibly marked and transformer installations must be protected from fire hazards and unauthorized access. See Transformer rules in 1926.405(j)(5)(ii)–(iv).

• Additional vault requirements: vaults must contain fire/combustible liquids, prevent unauthorized access, allow inside egress (locks openable from inside), exclude foreign pipes/ducts, and prohibit storage of materials in the vault (1926.405(j)(5)(vi)–(viii)).

• Practical point: label voltage levels on equipment and keep combustible materials away from transformers.

All capacitors (except surge or component capacitors) must have an automatic means to drain stored charge and keep them discharged after disconnection; capacitors over 600 volts must have interlocked isolating or disconnecting switches or prominently displayed caution signs to prevent switching of load current. See Capacitor drainage in 1926.405(j)(6)(i) and Over-600 volt additional requirements in 1926.405(j)(6)(ii)(A).

• Practical safety tip: include automatic bleeder devices or grounded discharge paths and lockout/tagout procedures where appropriate; add visible warnings on high-voltage capacitor installations.

Portable cables must not be operated with splices unless the splices are permanent molded, vulcanized, or equivalent type. See the general provision in 1926.405 that requires portable cables to avoid non-permanent splices and to have strain relief at connections and terminations.

• Practical note: if a field splice is necessary for a portable cable, use a listed permanent splice assembly and provide proper strain relief and locking connectors to prevent opening while energized.

Portable lamps must be wired with flexible cord and an attachment plug that is polarized or of the grounding type; if the lamp uses an Edison-type lampholder, the grounded conductor must be identified and attached to the screw shell and the identified blade of the plug. See Portable lamp wiring in 1926.405(j)(1)(iii) and the specific requirement about grounded conductors for Edison lampholders in 1926.405(j)(1)(iii).

• Practical tip: use three-conductor cords and a grounding-type plug when metal parts could become energized; clearly mark (or color) the grounded conductor to avoid miswiring.