Which insulation requirement applies to the PBB?

• A. Must be insulated from support structure
• B. Must be grounded to earth
• C. Must be painted to a color code
• D. Must be insulated from electrical components

Answer: (A)

The key idea is electrical isolation of the PBB from the mounting support. If the PBB’s energized parts could touch the metal frame or support, that frame—often bonded to earth—could become energized, creating a shock hazard and potentially a fault path that undermines overcurrent protection. By insulating the PBB from the support structure, you eliminate that undesired conductive path and keep the live parts isolated where they cannot contact the frame or other grounded metal.

Grounding the PBB to earth would introduce a different fault path and isn’t the insulation requirement here. Painting to a color code isn’t a functional safety measure for isolation, and insulating only from other electrical components doesn’t address the risk of energizing the support structure itself.