Temporary wiring is not an “anything goes” situation. Energized electrical systems and circuits, even if only temporary, present hazards for electrical workers and others in construction. Safe work practices should always be applied when working on temporary wiring.

Electrical contractors should plan for the temporary wiring anticipated for each project. They are usually responsible for installing the permanent wiring during construction, and each project usually requires a minimum amount of temporary wiring that must be installed and used by all the trades.

Meeting the right requirements

Temporary wiring must meet National Electrical Code requirements and be installed and maintained by qualified persons that apply safe work practices in compliance with industry standards. Article 590 provides minimum requirements for installing temporary electrical power and lighting. 

NFPA 70E, Standard for Electrical Safety in the Workplace, provides the requirements for workplace safety. Whether electrical workers are handling temporary or permanent wiring, safe work practices are required. Let’s review the basic requirements for temporary wiring and address some important issues about workers’ responsibilities.

Temporary electrical installations must meet installation requirements in the NEC. General Code requirements apply to temporary electrical installations except as specifically modified by Article 590. Section 590.3 addresses the time duration that temporary wiring installations are permitted. For construction, remodeling, maintenance, repair or demolition of buildings, structures, equipment or similar activities, temporary installations shall be permitted for the length of time needed. For emergencies, tests and experiments, temporary installations are also permitted for the duration.

Diligence to safety

Perhaps many in the business treat the installation of temporary wiring as less important because it will not be there long, or because only qualified persons will work on it and be exposed to the hazards. It is important that you do not operate with these assumptions. Think about the job site you are currently working and the condition of the temporary power and lighting. Chances are it may need some serious thought and a closer look when you return.

Electrical safety in the workplace requires contractor diligence. Temporary electrical systems are worked on and modified frequently during the construction project, so, safe work practices should be applied.

Plan, plan and plan some more

NFPA 70E applies to the work associated with temporary installations and the electrical construction for the permanent building wiring system. Safe work practices are required regardless because the hazards are the same. 

The most effective method of working safely on electrical wiring systems is to disconnect the power and establish an electrically safe work condition. This is easily accomplished, especially on temporary circuits, and should be common practice. Often workers treat energized temporary wiring as less dangerous and attempt to justify working on it while energized—not a good idea. It is important to plan your work and work your plan.

Electrical work requires planning and execution, even with temporary wiring. There are serious responsibilities associated with installing and maintaining temporary electrical wiring on construction sites. Typically, the larger the construction site, the more temporary wiring is involved.

Temporary wiring usually includes all the elements of permanent wiring systems such as the service, feeders, branch circuit wiring for power and lighting outlets. Overcurrent protection and conductor sizing must meet the requirements in Article 240 and 310, respectively, and grounding and bonding must comply with Article 250. The wiring method used to install temporary circuits is usually one less than required for the building’s permanent wiring, and it should be adequately supported and secured and as protected from physical damage as is practical and secure.

Electrical contractors should maintain temporary wiring in a safe, Code-compliant condition throughout the project’s duration. Where circuits for power and lighting must be extended or rerouted to accommodate the various crafts or phases, it should be done with the power disconnected, locked out and tagged if applicable.

The NEC requires all temporary wiring to be removed when the project is completed, including accessible and inaccessible wiring, which can create some interesting challenges. See NEC 590.3(D) for installation removal requirements.