Temporary lighting in a new basement
What's wrong here?
- The lamps on the temporary lighting string have no guards
- Temporary branch circuits must be NM cable or another Chapter 3 wiring method, not flexible cord
- Temporary lighting may stay in place for no more than 90 days
- Nothing. This installation is compliant
Show the answer and the code reference
The answer
The bare bulbs in the temporary lighting string are not protected by guards or luminaires.
Correct choice: 1. The lamps on the temporary lighting string have no guards
590.4(F) requires every lamp used for general illumination on temporary wiring to be protected from accidental contact or breakage by a suitable luminaire or a lampholder with a guard. On a jobsite, framers swing lumber and drywall sheets and carry ladders right through these strings; an unguarded bulb gets broken, leaving a live filament or exposed base contacts at head height, and a hot lamp against sawdust or insulation is an ignition source. The cord, ties and GFCI feed can all be right and the string still fails without the cages.
How to fix it
Replace the string with one that has guarded lampholders, or snap listed lamp guards onto each lampholder. Keep the string tied up out of the way per 590.4(J).
Code references
NEC 2023 590.4(F) — Lamp Protection
All lamps for general illumination shall be protected from accidental contact or breakage by a suitable luminaire or lampholder with a guard. Brass-shell, paper-lined, or other metal-cased sockets shall not be used unless the shell is grounded.
Drills citing 590.4(F)NEC 2023 590.3(A) — During the Period of Construction
Temporary electric power and lighting installations shall be permitted during the period of construction, remodeling, maintenance, repair, or demolition of buildings, structures, equipment, or similar activities.
Drills citing 590.3(A)NEC 2023 590.4(C) — Branch Circuits
Temporary branch circuits shall originate in an approved power outlet, panelboard, or similar enclosure and may be run in cable assemblies or in multiconductor cords or cables identified in Table 400.4 for hard usage or extra-hard usage.
Drills citing 590.4(C)
2026 NEC:changed: The lamp protection rule moved from 590.4(F) to 590.6(E) and was reworded (the old word 'sockets' was dropped). A new allowance says nonreplaceable LED lamps built into a listed temporary lighting string need no guard (this matches UL 1088). The drill's string uses replaceable bulbs with no guards, so it still violates the rule, but the explanation and fix should cite 590.6(E) and mention the LED-string allowance. Confidence: medium
Minnesota
Minnesota adopted the 2023 NEC without amendment as the Minnesota Electrical Code (Minn. Rules 1315.0200; Minn. Stat. 326B.35), effective July 1, 2023, so 590.4(F) applies as published. Minnesota OSHA also adopts the federal construction standards by reference (Minn. Rules 5205.0010), and 29 CFR 1926.405(a)(2)(ii)(E) likewise requires lamps for general illumination to be protected from accidental contact or breakage. That edition governs permits filed through Aug. 16, 2026; permits filed on or after Aug. 17, 2026 fall under the 2026 NEC; see the 2026 NEC note on this drill for how the cited section fares there.
How Minnesota adopts the NECWhy the other choices are wrong
- Temporary branch circuits must be NM cable or another Chapter 3 wiring method, not flexible cord. 590.4(C) permits branch circuits during construction to be run in hard-usage or extra-hard-usage flexible cord or cable, which is what temporary lighting strings use.
- Temporary lighting may stay in place for no more than 90 days. The 90-day limit in 590.3(B) is for holiday decorative lighting. Construction temporary wiring is permitted for the duration of construction under 590.3(A).
- Nothing. This installation is compliant. Every lamp for general illumination on temporary wiring must be protected by a luminaire or a lampholder with a guard (590.4(F)).