Where power-limited conductors are installed in the same enclosure as power and lighting conductors, they must have a separation of at least?

• A. 1/8 inch
• B. 1/4 inch
• C. 1/2 inch
• D. 3/8 inch

Answer: (B)

When power-limited conductors share the same enclosure with power and lighting conductors, a physical separation is required to prevent interference, heat transfer, and potential fault paths from one circuit affecting the other. The specified separation to meet this safety and insulation boundary is one-quarter inch. This air gap helps keep power-limited circuits—like fire alarm signaling—protected from the effects of higher-voltage or higher-current circuits in the same box. If you can’t maintain that air gap, a listed barrier between the circuits or placing them in separate compartments is needed to achieve the same level of separation. Smaller gaps wouldn’t satisfy the requirement, while larger gaps are acceptable but not necessary beyond the minimum.