Master Electrician Exam (NEC)Special Occupancies, Equipment, and ConditionsMedium
A master electrician is installing temporary power for a construction site. The temporary service will be supplied by a 200A panelboard. Which of the following statements is true regarding the overcurrent protection and grounding requirements for this temporary installation according to the NEC?
- AThe temporary service must be supplied directly from the permanent utility transformer, bypassing any main overcurrent protection.
- BFeeder and branch-circuit conductors are permitted to be run along the ground without mechanical protection.
- CAll 125-volt, single-phase, 15- and 20-ampere receptacles must have GFCI protection, regardless of location.
- DThe grounding electrode system for temporary installations is not required to be as robust as for permanent installations.
Show answer & explanationAnswer & explanation
Correct answer: C. All 125-volt, single-phase, 15- and 20-ampere receptacles must have GFCI protection, regardless of location.
NEC 590.6(A) mandates that all 125-volt, single-phase, 15- and 20-ampere receptacles that are not part of the permanent wiring of the building or structure and are used for temporary wiring must have ground-fault circuit interrupter protection for personnel.
Why the other options are wrong
- A. All services, temporary or permanent, must have main overcurrent protection. Bypassing it is a severe safety violation.
- B. Feeder and branch-circuit conductors for temporary wiring must be protected from physical damage, typically by being elevated or run in conduit, not simply laid on the ground (NEC 590.4(B)).
- D. Temporary installations still require a robust grounding electrode system for safety, as specified in NEC 250 and 590.4(D).
Temporary Wiring GFCI (NEC)
For temporary electrical installations, all 125V, single-phase, 15A and 20A receptacles are required to have ground-fault circuit interrupter (GFCI) protection for personnel, ensuring safety on construction sites and similar temporary setups.
- Applies to 125V, 15A & 20A receptacles.
- Mandatory for temporary wiring (NEC 590.6(A)).
- Protects personnel from electrical shock.
Memory trick: Temporary Power: Always GFCI, Always Protected, Always Grounded.