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NEC Article 527 - Temporary Installations 6/9/2004
By Mike Holt for EC&M Magazine

By following Article 527, you can avoid the permanent consequences of unsafe temporary installations.

James Bond has a license to kill. Sometimes, temporary installations look like something rigged up under that same license. While many of us think of the NEC as a standard that helps us ensure the safety of the end-user, it also helps us ensure the safety of all the trades working on any given project where temporary electrical installations are part of the picture.

When you think of the Authority Having Jurisdiction (AHJ), don't you usually think of the electrical inspector? The inspector isn't the only AHJ for a given job, especially while it is in progress and there is temporary power or light. The general contractor and OSHA can enforce temporary installation rules. So can the insurance providers of such parties as your company, the general contractor, other trades, and the property owner.

[527.1] The requirements of Article 527 apply to all temporary power and lighting installations, including power for construction, remodeling, maintenance, repair, demolitions, and decorative lighting. This article also applies when temporary installations are necessary during emergencies or for tests and experiments. All of the requirements of the NEC apply to temporary installations unless specifically modified in this article. Those modifications are very few.

Certain venues have additional requirements. Temporary installations for trade shows must comply with Article 518. Temporary installations for carnivals, circuses, fairs and similar events must comply with Article 525.

Time constraints

[527.3] Temporary installation rules do provide some savings in cost and time, compared to permanent rules. At one time, electricians would install temporary power or lighting under those looser Code requirements and installations would be "temporary" on a permanent basis. Thus, time constraints made their way into the NEC and are as follows:

Construction Period. You can use temporary electrical power and lighting installations during the period of construction, remodeling, maintenance, repair or demolition of buildings, structures, equipment, or similar activities.

Decorative Lighting. You can use temporary electrical power for decorative lighting for up to 90 days.

Emergencies and Tests. You can use temporary electrical power and lighting installations for the duration necessary for emergencies or for tests and experiments. You must remove all temporary installations immediately upon the completion of the purpose for which they were installed.

Areas of Application

In 527.4, the NEC provides specific rules for each major area of application. This is really the meat of the Article. What's especially useful about this arrangement of the NEC is you can refer to exactly what you are working on. For example, if you are providing a temporary branch circuit, you can refer to 527.4(C) and see what the requirements are. The NEC addresses these areas of application in a logical order, beginning with the service entrance:

Services. You must install a service per Article 230. No slack, here. You must treat a service as permanent, even if it's temporary.

Feeders. You cannot use open conductors for temporary feeder installations. However, you can use cable assemblies, hard-usage cords, extra-hard usage cords, and NM cable. Exception: You can use individual open conductors for feeders where the individual open conductors are accessible only to qualified personnel.

Branch Circuits. You cannot use open branch-circuit conductors (such as "festoon lighting") for temporary installations However, you can use cable assemblies, hard-usage cords, extra-hard usage cords, and NM cables (see Figure 2 un527-02 527-04C.cdr). Exception: You can use open wiring for branch circuits in holiday decorative lighting under certain conditions: the circuit voltage-to-ground does not exceed 150V, the conductors are not subjected to physical damage, and the conductors are supported on insulators at not more than 10 ft intervals.

Receptacles. Receptacles must be of the grounding type and have the equipment grounding (bonding) terminal of the receptacle grounded (bonded) to an equipment grounding conductor [250.118], in accordance with 250.146. This does not mean driving a ground rod and bonding to it without bonding to the rest of the system. Remember, electricity always seeks to get back to the source, not to the earth.

Lighting vs. receptacles. On a construction site, you can't put lighting and receptacles on the same circuit. This keeps the lights from going out if the GFCI opens. Where you are using a multiwire circuit, the same principle applies. Put lighting on one circuit and receptacles on the other.

Disconnecting Means. All ungrounded circuit conductors must have a disconnecting means. This can be a switch or a circuit breaker. Ungrounded circuit conductors of a multiwire branch circuit need a disconnecting means at the panelboard, and it must open all of the ungrounded conductors simultaneously. If the multiwire circuit uses single-pole circuit breakers, you must use an approved handle tie to secure the trip handles together. For additional requirements for multiwire branch circuits, see 210.4 and 300.13(B).

Lamp Protection. You must protect lamps from accidental contact by using a suitable luminaire or a lampholder with a guard.

Splices. On construction sites, you don't have to put splices of cords or nonmetallic cables in boxes. However, this doesn't mean you can use "twist and tape" or other unapproved methods for making those splices. You must use methods and devices suitable for the purpose.

Protection from Accidental Damage. You must protect cables and flexible cords from accidental damage, and from sharp corners and projections. You must also provide protection for cables and flexible cords when passing them through doorways or other pinch points.

Terminations at Devices. Cables and flexible cords entering enclosures must be secured to the enclosure with fittings designed for the purpose. You can't just stick them through an opening in an enclosure. The intent is to prevent stress on cables and cable terminations.

Support. Make sure you support cables, cable assemblies, and flexible cords at intervals that ensure protection from physical damage. To provide this support, use staples, cable ties, straps or other similar products designed to not damage the cable or cord assembly. The AHJ can make specific cable support requirements, based on job site conditions. Per Section 230.10, you can't use trees or other vegetation for support of overhead spans of branch circuits or feeders.

GFCI Protection

[527.6] You must provide ground-fault protection for temporary wiring used for construction, remodeling, maintenance, repair or demolition of buildings, structures, equipment or similar activities.

All 125V, 15A, 20A, and 30A receptacles used for temporary power must have GFCI protection. You can provide GFCI protection via circuit breakers, receptacles, cord sets or other devices such as GFCI adapters incorporating listed GFCI protection (see Figure 4 un527-04 527-06A 01.cdr).

You must provide GFCI protection for receptacles that are part of the permanent wiring of the building and are used for temporary power (see Figure 5 un527-05 527-06A 02.cdr). Exception: You don't need to provide GFCI protection for receptacles located in industrial establishments where only qualified personnel are involved in maintenance and are following an Assured Equipment Grounding Conductor Program (AEGCP).

Receptacles rated other than 125V, 15A, 20A, or 30A that supply temporary power to equipment used by personnel during construction, remodeling, maintenance, repair or demolition of buildings, structures, equipment, or similar activities must comply with either GFCI protection or an AEGCP (see Figure 6 un527-06 527-06B.cdr). You can use GFCI protection and an AEGCP on the same job, if you want to-they are not mutually exclusive.


An AEGCP requires grounding tests of cord sets, receptacles and cord-and-plug-connected equipment. All equipment grounding conductors must be tested for continuity. Each receptacle and attachment plug must be tested for the correct attachment of the equipment grounding conductor. The results of these tests must be recorded and made available to the AHJ. The tests must be performed before:

The first use on-site

When there's evidence of damage

Before equipment is returned to service following repairs

At intervals not exceeding 3 months.


For wiring over 600V, nominal, you must provide suitable fencing, barriers, or other effective means to limit access to only qualified personnel. Common sense and or the AHJ may require such guarding for lower voltages as well, based on job site conditions.

How can you sum up the requirements for temporary installations? The first rule is they must be truly temporary. Service entrances have no temporary allowances. Other applications allow you to use cords and cable assemblies rather than installing raceways, and they allow you to place splices outside of boxes. But, there's a trade-off. You must also provide the additional protection of a GFCI or AEGCP. In addition to satisfying the AHJ, you ensure your own safety when your temporary installation conforms to Article 527.