When bare conductors are installed with insulated conductors, their ampacities shall be limited to which of the following?

When bare conductors are installed with insulated conductors, their ampacities shall be limited to which of the following?

• A. the highest temperature rating for any insulated conductor
• B. the lowest temperature rating for any of the insulated conductors
• C. the average temperature rating
• D. the insulation type of the bare conductor

Answer: (B)

When multiple conductors share the same space, the heat they generate must be considered for the whole group. Each insulated conductor has a maximum operating temperature based on its insulation. In a mix of bare and insulated conductors, the ampacity is limited to the lowest temperature rating among the insulated conductors in that group. This ensures the insulation of the conductors isn’t overheated by the current carrying in the bundle. Bare conductors don’t contribute an insulation rating to limit in themselves, so the determining factor is the weakest insulation rating present. Choosing the highest rating would risk exceeding the insulation limits, and averaging ignores the worst-case thermal condition.

When multiple conductors share the same space, the heat they generate must be considered for the whole group. Each insulated conductor has a maximum operating temperature based on its insulation. In a mix of bare and insulated conductors, the ampacity is limited to the lowest temperature rating among the insulated conductors in that group. This ensures the insulation of the conductors isn’t overheated by the current carrying in the bundle. Bare conductors don’t contribute an insulation rating to limit in themselves, so the determining factor is the weakest insulation rating present. Choosing the highest rating would risk exceeding the insulation limits, and averaging ignores the worst-case thermal condition.