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.
About the Author
Mike Holt
Mike Holt is the owner of Mike Holt Enterprises (www.MikeHolt.com), one of the largest electrical publishers in the United States. He earned a master's degree in the Business Administration Program (MBA) from the University of Miami. He earned his reputation as a National Electrical Code (NEC) expert by working his way up through the electrical trade. Formally a construction editor for two different trade publications, Mike started his career as an apprentice electrician and eventually became a master electrician, an electrical inspector, a contractor, and an educator. Mike has taught more than 1,000 classes on 30 different electrical-related subjects — ranging from alarm installations to exam preparation and voltage drop calculations. He continues to produce seminars, videos, books, and online training for the trade as well as contribute monthly Code content to EC&M magazine.