Understanding NEC Article 590: Temporary Installations

NEC Article 590 outlines the requirements for temporary electrical power and lighting installations. These installations are common at construction sites, events, emergencies, and other temporary setups, ensuring safety while addressing the unique challenges of temporary wiring systems.

Scope of Article 590

This article applies to:

• Temporary power and lighting installations at transient or permanent locations, such as:
  • Construction and demolition sites.
  • Fairs, festivals, and holiday displays.
  • Emergency or experimental setups.

Key Requirements for Temporary Installations

1. Time Constraints
   • Construction and Maintenance: Temporary systems are allowed for the duration of the project.
   • Holiday Displays: Limited to a maximum of 90 days.
   • Emergency and Test Systems: Permitted as needed for emergencies, experiments, and developmental work.
   • All temporary wiring must be removed immediately after the purpose is completed.
2. Wiring Methods
   • Wiring must follow general NEC requirements unless modified by Article 590.
   • Flexible cords and cables can be used but must be suitable for extra-hard usage in demanding environments.
   • Vegetation cannot support wiring except for holiday lighting under specific conditions.
3. Ground-Fault Circuit-Interrupter (GFCI) Protection
   • GFCI protection is mandatory for:
     • 15-, 20-, and 30-amp receptacles used by personnel.
     • Receptacles on generators of 15 kW or less.
   • Exceptions exist for industrial facilities where qualified personnel supervise.
4. Receptacles and Branch Circuits
   • Receptacles must include grounding conductors, and circuits must originate from approved outlets or panels.
   • Circuits used for lighting and receptacles must remain separate.
5. Protection and Support
   • Lamps must be enclosed to prevent accidental contact or breakage.
   • Flexible cords and cables must be protected from sharp edges and physical damage.
   • Temporary wiring must be adequately supported to prevent sagging or physical harm.
6. Disconnecting Means
   • Each temporary circuit must have a disconnecting device to isolate all ungrounded conductors.

Special Requirements

1. Decorative Lighting
   • Holiday and similar lighting must be listed and labeled for temporary use.
   • Wiring used in displays must be removed after 90 days.
2. Overcurrent Protection
   • Devices must be inspected and maintained to ensure functionality in demanding environments.
   • Current-limiting protection is required for services with high fault currents exceeding 10,000 amperes.

Applications

NEC Article 590 is critical for ensuring safe electrical setups in:

• Construction Sites: Power tools, lighting, and temporary offices.
• Festivals and Events: Power distribution for vendors and stages.
• Emergency Responses: Temporary shelters and critical services.

Conclusion

NEC Article 590 provides a framework for safely managing temporary electrical systems. By specifying proper wiring, grounding, and protective measures, this article minimizes risks and ensures compliance during temporary installations.