Master Electrician Exam (NEC)Services, Feeders, and Branch CircuitsMedium
A utility company is providing a 600A, 480Y/277V, 3-phase, 4-wire service to a new commercial building. The service drop conductors from the utility pole to the service point on the building are installed over a public street. What is the minimum vertical clearance required for the service drop conductors above the public street?
- A12 feet
- B15.5 feet
- C18 feet
- D10 feet
Show answer & explanationAnswer & explanation
Correct answer: C. 18 feet
According to NEC 230.24(B)(1), service drop conductors shall have a minimum clearance of 18 feet above public streets, alleys, roads, driveways on other than residential property, and other areas subject to truck traffic. This is for circuits not exceeding 600V.
Why the other options are wrong
- A. This clearance is for driveways on residential property and commercial areas not subject to truck traffic.
- B. This clearance is for areas where vehicles are likely to pass, but not specifically truck traffic.
- D. This clearance is for residential driveways and areas only accessible by pedestrians.
Service Drop Clearance (Public Streets)
Service drop conductors must maintain specific minimum vertical clearances from various surfaces to prevent accidental contact and ensure public safety.
- Clearances vary depending on the area below the conductors (e.g., pedestrian, vehicle, road).
- NEC 230.24(B) specifies these clearances.
- Public streets typically require the highest clearances due to truck traffic.
Memory trick: Clearance: higher for traffic, lower for feet.