It’s often unclear what clearance you really need for overhead service conductors. Just looking through the NEC requirement [230.24], you see numbers ranging from 3 ft to 18 ft. And then at the end of 230.24, you see references to clearance requirements in three other Articles. Fortunately, you don’t have to read all this.
To know the minimum clearance for a particular application:
- Pick from the five types of applications [230.24(A) – (E)] that fits your installation. Because only one will fit your application, you can ignore the other four subsections.
- Read through the subsection and look for the particulars that match your application.
The minimum clearance might not be the right clearance, however. For example, suppose your service entrance is going to be on the east side of the building and it so happens your chillers are also going to go on that side. An 8-ft clearance above the roof isn’t going to accommodate the crane boom for installing or (eventually) replacing those chillers. If it’s early enough in the project, you can move something (most likely the service entrance) to avoid a conflict. However, you might be stuck with simply increasing the conductor overhead clearance.
Always look for ways people or vehicles might come into contact with the incoming power and increase clearances accordingly.
