Temporary Wiring - Anything Goes?

By Michael Johnston | Apr 15, 2009
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It’s only temporary wiring, so what’s the problem? Ever get the feeling that temporary electrical wiring is treated as an afterthought, if even considered at all? Many electrical workers treat it as though it is less dangerous than permanent electrical installations and those associated hazards.

Electrical contractors are usually responsible for installing the permanent wiring during construction. Each construction project usually requires a minimum amount of temporary electrical wiring that must be installed and used by all the trades during the construction of buildings or structures. Why is it that temporary electrical wiring on projects is treated differently than permanent electrical wiring with regard to the workmanship, wiring methods, and applying safe work practices? Is it because it is, as many say, only temporary?

Temporary wiring must meet the requirements of the National Electrical Code (NEC) and be installed and maintained by qualified persons that apply safe work practices in compliance with industry standards. Article 590 of the Code provides minimum requirements for installing temporary electrical power and lighting. NFPA 70E Standard for Electrical Safety in the Workplace provides the requirements for electrical workplace safety. Whether electrical workers are handling temporary wiring or permanent wiring, safe work practices are required. This article takes a look at some of the basic requirements for temporary wiring and addresses some of the important issues regarding the responsibilities of electrical contractors and workers.


Length of time

How temporary is temporary? Temporary is a condition of time. The only significant difference between the temporary wiring and permanent wiring of a building or structure is the length of time it is in service. This is true for all temporary wiring except the wiring methods and level of personnel protection.

The NEC clearly indicates that all other requirements apply to temporary electrical installations except as specifically modified by Article 590. Section 590.3 addresses the duration of time 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 these events. A period of 90 days is specified for holiday decorative lighting and similar installations. For emergencies, tests, and experiments temporary installation are permitted for the duration of each. [NEC 590.3(A), (B), and (C)]


Perhaps many in the business discount the installation of temporary wiring as less important because it is not going to be there that long or because only qualified persons will work on it and be exposed to temporary wiring hazards. These are important points that should not be taken lightly. Just think about the jobsite you are currently working on. What does the temporary power and lighting circuitry look like, what condition is it in? Does it provide adequate service? Are there any obvious hazards? Chances are you have to give it some serious thought and a closer look when you return to the site.

Safe work practices

Electrical safety in the workplace requires diligence on the part of the contactor and the individual workers. Temporary electrical installations have to meet the installation requirements of the NEC. These are systems that are worked on and modified frequently during the course of the construction project. When installing temporary electrical wiring for construction safe work practices should be applied.

NFPA 70E Standard for Electrical Safety in the Workplace 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 the common practice. Often workers treat energized temporary wiring as less dangerous and attempt to justify working on temporary wiring while it is energized. It’s only temporary right? Does this sound familiar?

Planning the temporary installation

Plan your work, and work your plan. Failing to plan is essentially planning to fail. Ever heard these phrases? How much planning goes into the temporary electrical wiring on your jobsite? Is it an afterthought? Was it covered in the estimate of the project or a time and material arrangement? Perhaps it is subcontracted.

Electrical work requires planning and execution, even the 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. Temporary wiring often 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 methods used to install temporary circuits is usually a method less than is required for the permanent wiring of the building. It should be adequately supported and secured and protected from physical damage as practical. Temporary electrical wiring should be inherent to the planning stages of every job even the estimate. There appears to be vast inconsistencies in how this part of a construction project is managed. Some contractors have a consistent method for every job and even use prefabricated power distribution assemblies. Others appear to handle temporary wiring for construction on a day to day basis. This is where problems of inadequacy can show up in the form of unsafe conditions. It’s only temporary right?

Maintaining and extending temporary wiring during construction

Temporary wiring tends to get abused, sometimes severely during the course of construction. Contractors should maintain temporary wiring in a safe, code-compliant condition throughout the duration of the project. This aspect of temporary wiring is usually overlooked until something happens. Damaged circuits should be repaired or replaced. Where circuits for power and lighting have to be extended or re-routed to accommodate the various crafts or phases of construction, it should be done with the power disconnected and locked out and tagged if applicable. Circuit directories are a challenge to create and maintain on construction projects, but are essential for worker safety. Safe work practices apply to temporary wiring yet many disregard the safety rules. Disconnect the electrical power to the temporary wiring so it can be worked on safely. Always follow the applicable electrical safety rules when working with temporary wiring or permanent wiring installations. The hazards are essentially the same.


The NEC requires temporary wiring to be removed when the project is completed. Notice that this requirement apples to all temporary wiring and does not distinguish between accessible and inaccessible wiring. This can create some interesting challenges on jobsites. Many completed construction projects today still have temporary wiring strung in concealed spaces, and some is still connected! Temporary wiring is not as substantial as the permanent wiring of a building and should be disconnected and removed when the construction or purpose for the temporary wiring is completed. See NEC 590.3(D) for installation removal requirements.


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 strive to plan for the amount of temporary wiring anticipated for each construction project. Obviously the temporary electrical wiring needed for a convenience store project is far less and much different that that necessary for high rise construction projects. Planning should result in consideration of capacity, distribution routing, wiring methods, and removal. The contractor should also include planning for flexibility in the installation that will accommodate the changing needs of a construction site in a manner that meets all safety installation rules and protects workers from the inherent hazards associated with construction work. It’s only temporary so it should be easy to install according to the NEC rules and worked on in a safe manner that meets electrical workplace safety requirements. NECA is in the final stages of development of NEIS 200 Standard for Installing and Maintaining Temporary Electric Power at Construction Sites. Watch for this standard to be available in the fall of 2008.

JOHNSTON is NECA's executive director of standards and safety. He is former director of education, codes and standards for IAEI; a member of the IBEW; and an active member of the NFPA Electrical Section, Education Section and the UL Electrical Council. Reach him at [email protected].

About The Author

A man, Mike Johnston, in front of a gray background.

Michael Johnston

NECA Executive Director of Codes and Standards

JOHNSTON is NECA’s executive director of codes and standards. He is a member of the NEC Correlating Committee, NFPA Standards Council, IBEW, UL Electrical Council and NFPA’s Electrical Section. Reach him at [email protected]


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