What insulation rating must branch circuit conductors maintain if located within 3 inches of a ballast?

The correct insulation rating for branch circuit conductors located within 3 inches of a ballast is 90ºC. This rating is essential due to the heat generated by the ballast during operation. Ballasts can generate significant heat, and if conductors are too close without proper insulation ratings, there's a risk of the insulation degrading, which can lead to short circuits, electrical faults, or even fire hazards.

Using conductors rated for higher temperatures, like the 90ºC rating, provides assurance that the conductors can withstand the elevated temperatures without compromising their insulation integrity. This is particularly important in scenarios where there is reduced air circulation or enhanced heat transmission due to close proximity to heat-generating components.

Conductors with lower temperature ratings, such as 60ºC, would not provide adequate protection in these circumstances and could fail prematurely. Similarly, while a 75ºC rating is better than 60ºC, it still does not meet the necessary criteria for safety in this specific installation scenario. A 100ºC rating, while higher, is not typically required for standard installations near ballasts unless specified by unique environmental conditions or regulations. Thus, the 90ºC rating strikes the appropriate balance between safety and practicality for wiring in such applications