Q. What is the minimum vertical clearance for overhead service conductors above a roof?

A. Overhead service conductor spans must maintain the vertical clearances as follows [230.24(A)]: a minimum of 8 ft above the surface of a roof for a minimum distance of 3 ft in all directions from the edge of the roof.

Exception 2: If the slope of the roof exceeds 4 in. of vertical rise for every 12 in. of horizontal run, 120/208V or 120/240V overhead service conductor clearances can be reduced to 3 ft over the roof.

Exception 3: If no more than 6 ft of conductors pass over no more than 4 ft of roof, 120/208V or 120/240V overhead service conductor clearances over the roof overhang can be reduced to 18 in.

Exception 4: The 3 ft vertical clearance for overhead service conductors that extends from the roof doesn't apply when the point of attachment is on the side of the building below the roof.

Exception 5: If the voltage between conductors doesn't exceed 300V — and the roof area is guarded or isolated — a reduction in clearance to 3 ft is permitted.