How far must cable, raceway, or box be installed from the lowest surface of metal-corrugated sheet roof decking?

The requirement for installing cable, raceway, or boxes from the lowest surface of metal-corrugated sheet roof decking is to prevent potential damage and ensure safety. The correct distance of 1 1/2 inches provides adequate space to avoid contact with any condensation that may form on the roofing material or the potential for the roofing surface to distort due to temperature changes. This clearance helps minimize the risk of moisture ingress, which could lead to electrical hazards or damage to the conductors and insulation. By maintaining this distance, it promotes both electrical safety and long-term reliability of electrical installations in those areas.