Master Electrician Exam (NEC)Services, Feeders, and Branch CircuitsHard
A master electrician is installing a 100A, 120/240V single-phase service for a dwelling unit. The service entrance conductors are 2 AWG copper. If the service is supplied by overhead conductors and the point of attachment is 15 feet above finished grade, what is the minimum clearance required for the service drop conductors over a public street?
- A18 feet
- B12 feet
- C10 feet
- D15.5 feet
Show answer & explanationAnswer & explanation
Correct answer: A. 18 feet
According to NEC 230.24(B)(1), service drop conductors shall have a minimum clearance of 18 feet at the point of attachment to the building or structure, or above sidewalks, or above finished grade where the conductors pass over commercial areas, parking lots, or other areas subject to truck traffic, or where the conductors pass over public streets, alleys, roads, or other areas subject to vehicular traffic other than truck traffic.
Why the other options are wrong
- B. 12 feet is for residential driveways and commercial areas not subject to truck traffic (NEC 230.24(B)(1) Exception No. 2).
- C. 10 feet is for areas accessible to pedestrians only (NEC 230.24(B)(1) Exception No. 1).
- D. 15.5 feet is for areas subject to truck traffic over commercial property where the voltage does not exceed 300V to ground.
Service Drop Clearance (Public Street)
Specific minimum vertical clearances required by the NEC for overhead service drop conductors above various surfaces, including public streets, to ensure safety.
- Reference NEC 230.24(B).
- Clearance varies based on the surface beneath and voltage.
- Public streets require greater clearance due to vehicular traffic.
Memory trick: Service drops are like 'air traffic lanes'; different zones need different altitudes.