A cable, raceway, or box installed under metal-corrugated sheet roof decking shall be supported so the top of the cable, raceway, or box is not less than how many inches from the lowest surface of the roof decking?

The correct answer reflects the requirement that cables, raceways, or boxes installed under metal-corrugated sheet roof decking must be positioned a minimum of 1½ inches above the lowest surface of the roof decking. This specification is essential for ensuring that the electrical installations are adequately protected from potential moisture accumulation or debris that could lead to damage or pose safety hazards.

Maintaining this distance adds a layer of safety by mitigating the risk of wire insulation degradation and ensures compliance with electrical codes that prioritize the protection of electrical components. The 1½ inch clearance strikes a balance between sufficient safety margins while still accommodating practical installation practices in various environments. Therefore, adhering to this specific height helps ensure longevity and safety in electrical installations, particularly in areas where exposure to environmental conditions is a concern.