Service Mast Regulations

Overhead service conductors installed in a cable, or as individual open conductors, must be at least 3 ft from doors, porches, balconies, ladders, stairs, fire escapes, or similar locations. They must also be at least 3 ft from windows that open. If they run above a window, you don’t have to maintain the 3 ft distance to that window (Fig. 1).

Fig. 1. Overhead conductors must maintain a clearance of 3 ft from windows that open, doors, porches, balconies, ladders, stairs, fire escapes, or similar locations.

Maintain a vertical clearance of at least 10 ft above platforms, projections, or surfaces from which people might reach an overhead conductor. This vertical clearance must be maintained for 3 ft, measured horizontally from the platform, projections, or surfaces from which people might reach them, except:

  • If the slope of the roof exceeds 4 in. of vertical rise for every 12 in. of horizontal run, 120/208V or 120/240V conductor clearances can be reduced to 3 ft over the roof.
  • If no more than 6 ft of conductors pass over no more than 4 ft of roof, 120/208V or 120/240V conductor clearances over the roof overhang can be reduced to 18 in. (Fig. 2).

Fig. 2. For 120/208V or 120/240V circuits, conductor clearance can be 18 in., if no more than 6 ft of conductors pass over no more than 4 ft of roof.

 

Don’t install service conductors under an opening through which materials might pass, nor where they will obstruct entrance to building openings. Finally, don’t use vegetation as support.

Service-drop conductors must have adequate mechanical strength, and they must have sufficient ampacity to carry the load.

Service-drop conductor vertical clearances

Service-drop conductor spans must maintain a minimum of 8 ft above a roof surface, for a minimum distance of 3 ft in all directions from the edge of the roof. There are exceptions, however. For example, if the slope of the roof exceeds 4 in. of vertical rise for every 12 in. of horizontal run, you can reduce the clearances of 120/208V or 120/240V conductors to 3 ft over the roof.

Overhead conductor spans must maintain the following vertical clearances:

  • 10 ft above finished grade, sidewalks, or platforms or projections from which they might be accessible to pedestrians for 120/208V or 120/240V circuits.
  • 12 ft above residential property and driveways, and those commercial areas not subject to truck traffic for 120/208V, 120/240V, or 277/480V circuits.
  • 18 ft over public streets, alleys, roads, parking areas subject to truck traffic, driveways on other than residential property, and other areas traversed by vehicles, such as those used for cultivation, grazing, forestry, and orchards.
Content retrieved from the EC&M