OSHA 1926.405 Temporary Wiring Checklist: Bid and Schedule Guide
Temporary electrical power and lighting create frequent coordination hurdles on commercial jobsites. For framing, drywall, ceiling, and interior contractors, temporary lines dictate how equipment runs, where scaffolding moves, and what safety responsibilities arise during active construction. Under eCFR OSHA § 1926.405, temporary wiring methods may be of a class less than what is required for a permanent installation, but strict federal rules govern how branch circuits, open conductors, flexible cords, and enclosures are configured and removed. Estimators pricing trade packages and general contractors coordinating trade flow must understand these operational mandates to price labor accurately and avoid unexpected work stoppages.
Checklist Item: Temporary Feeders and Open Conductor Spacing
Feeders and branch circuits distribute energy across active floor plates. When evaluating temporary power distribution during estimating or site prep, contractors should verify compliance against standard layout requirements:
- Origin of distribution: Feeders must originate in a distribution center, while branch circuits must originate in a power outlet or panelboard.
- Conductor routing: Conductors must be run as multiconductor cord or cable assemblies or within raceways. Where not subject to physical damage, conductors may be run as open conductors on insulators.
- Insulator support spacing: Runs of open conductors on insulators must be fastened at intervals not exceeding 10 feet (3.05 m).
- Floor clearance: No branch-circuit conductors shall be laid on the floor. When trade crews hang drywall or install ceiling grid, keeping conductors off the deck prevents physical crushing and tripping damage.
- Equipment grounding conductors: Each branch circuit supplying receptacles or fixed equipment must contain a separate equipment grounding conductor if the circuit is run as open conductors.
- Overcurrent protection: All conductors must be protected by overcurrent devices sized at their ampacity.
Checklist Item: Temporary Lighting Circuits and Lampholder Rules
General illumination on interior fit-outs demands consistent attention to avoid overloaded branch circuits and safety citations. The standard establishes strict separation between temporary lighting and tool power:
- Circuit separation: Receptacles for uses other than temporary lighting must not be installed on branch circuits that supply temporary lighting. In addition, receptacles cannot be connected to the same ungrounded conductor of multiwire circuits supplying temporary lighting.
- Bulb protection: All lamps for general illumination must be protected from accidental contact or breakage, and metal-case sockets must be grounded.
- Fixture suspension: Temporary lights must not be suspended by their electric cords unless the cords and lights are designed specifically for that means of suspension.
- Fixture dimensions and weight: A fixture that weighs more than 6 pounds (2.72 kg) or exceeds 16 inches (406 mm) in any dimension must not be supported by the screw shell of a lampholder.
- Disconnecting switches: Disconnecting switches or plug connectors must be installed to permit disconnection of all ungrounded conductors of each temporary circuit.
- Wet location lighting: Portable electric lighting used in wet or conductive locations, such as drums, tanks, and vessels, must operate at 12 volts or less, though 120-volt lights are permitted if protected by a ground-fault circuit interrupter.
Checklist Item: Flexible Cords, Extension Sets, and Splicing Limits
Flexible cords supply chop saws, screw guns, and mobile work lights across commercial floors. However, flexible cords cannot be treated as permanent building wiring. Estimators should account for proper cord classifications when verifying general tool packages on a bid day checklist:
- Cord duty ratings: Extension cord sets used with portable electric tools and appliances must be of the three-wire type and designed for hard or extra-hard usage. Types include hard service cord (types S, ST, SO, STO) and junior hard service cord (types SJ, SJO, SJT, SJTO) listed in ANSI/NFPA 70, Article 400, Table 400-4. Cords must be durably marked on the surface with their type designation, size, and number of conductors.
- Continuous lengths and splices: Flexible cords must be used only in continuous lengths without splice or tap. The sole exception allows hard service flexible cords No. 12 or larger to be repaired if spliced so that the repair retains the insulation, outer sheath properties, and usage characteristics of the cord.
- Prohibited placements: Flexible cords and cables must not serve as substitutes for fixed wiring, nor pass through holes in walls, ceilings, or floors, nor be attached to building surfaces, nor remain concealed behind walls, ceilings, or floors.
- Pinch points and strain relief: Flexible cords passing through doorways or pinch points must have protection to avoid damage. Strain relief must prevent pull from transmitting directly to joints or terminal screws.
Checklist Item: Cabinets, Enclosures, and High Voltage Guarding
Boxes and fittings house electrical junctions and must maintain continuous protection against moisture, abrasion, and accidental worker contact:
- Enclosure integrity: Conductors entering boxes, cabinets, or fittings must be protected from abrasion, and unused openings must be effectively closed. All junction boxes, pull boxes, and fittings require covers, and metal covers must be grounded.
- Damp and wet installations: Cabinets, cutout boxes, fittings, and panelboards in damp or wet locations must be installed to prevent moisture from entering or accumulating. Enclosures in wet locations must be weatherproof.
- Live part elevation: Fixtures, lampholders, and receptacles cannot have live parts normally exposed to contact, though rosettes and cleat-type lampholders located at least 8 feet (2.44 m) above the floor may have exposed parts.
- High voltage enclosures: For temporary wiring over 600 volts nominal, fencing or barriers must prevent access by unauthorized personnel. Pull boxes for systems over 600 volts must be permanently marked "HIGH VOLTAGE," and underground covers weighing over 100 pounds (43.6 kg) meet secure closure rules. Flexible cables for mobile equipment operating over 2000 volts must be shielded.
Factoring Removal into General Conditions and Schedules
Under OSHA § 1926.405, temporary wiring must be removed immediately upon completion of construction or upon completion of the specific purpose for which it was installed. When establishing bid pricing for general conditions, contractors must account for both installation and teardown labor. Omitting temporary electrical decommissioning from the final project schedule risks unanticipated site labor costs and delayed handover during final punch work.
Sources
eCFR: OSHA § 1926.405 Wiring methods, components, and equipment for general use
Published October 28, 2026. No affiliate links on this page. Facts come from the sources linked above; check them for updates.