For an exposed 480-volt control assembly, an electrical room is proposed as the guarding method discussed in 2023 NEC 110.27. Which access arrangement provides the required restriction?
- AA public corridor, provided that staff are told to avoid the assembly
- BAn unlocked room with only a warning sign on the door
- CA locked room whose key is available to all plant staff regardless of qualification
- A room or vault arranged so that access is limited to qualified persons
Where to look it up
https://www.nfpa.org/es/News-Blogs-and-Articles/Blogs/2022/11/30/Electrical-Room-Basics-Part-1
Why D is correct
The electrical-room method depends on actually limiting access to qualified persons. A sign, general instruction or shared staff key does not establish that restriction. NFPA’s explanation of the 2023 NEC describes a controlled electrical room or vault as one guarding approach; it does not say every electrical installation requires a separate room. Source: Dean Austin, NFPA, Electrical Room Basics, Part 1, November 30, 2022 (official Spanish edition). https://www.nfpa.org/es/News-Blogs-and-Articles/Blogs/2022/11/30/Electrical-Room-Basics-Part-1