National Electrical Code Top Ten Tips: Article 590, Temporary Installations
- Article 590 covers the installation of temporary power and lighting [590.1].
- Contrary to common misconception, temporary installation requirements are "shortcut tolerant." That isn't their purpose. In fact, all other Articles apply to these installations [590.2(A)] except for modifications provided in this Article. The purpose of this Article is to allow for the fact such installations will be removed within a short time of being installed.
- Temporary installations are acceptable only if approved based on the conditions of use and any special requirements of the temporary installation [590.2(B)].
- Temporary installations are, by definition, time-constrained. The NEC defines three periods: during construction, 90 days, and emergencies/tests [590.3].
- At the end of the period for which the installation was implemented, it must be removed [590.3].
- There are no special allowances for services. These must be installed as if they are permanent [590.4(A)]. It is common on tract home construction sites to ignore this requirement. Since the Code inspector presumably will visit only when the wiring is nearly done and a permanent service has been installed by the utility, many home builders mistakenly believe they get away with this. But it's gambling with people's lives. The goal isn't to avoid getting caught, it's to avoid getting dead.
- For feeders and branch circuits, the basic exception for temporary installations is you can wire the circuits using Type NM and Type NMC cables [590.4(B) and (C)]. Every other requirement still applies, and in some cases with even more stringency than for permanent installations; for example, all receptacles must be of the grounding type.
- Luminaires for temporary circuits have special requirements. For example, they must all have protection against accidental contact or breakage [590.4(F)].
- All temporary wiring must be ground fault protected [590.6]. The exception to this is on temporary receptacles where you have an assured grounding program. Such a program is so difficult to maintain and properly document that generally this exception is not an option.
- But some companies are successful with their assured grounding program. If you want to consider this, the requirements are in 590.6(B)(2).