Journeyman Electrician Exam (NEC)Wiring Methods and MaterialsHard
A licensed electrician is installing a 200-amp service entrance for a new single-family dwelling. The service conductors will be run through a 2-inch Rigid Metal Conduit (RMC) from the meter base to the service disconnecting means. According to NEC Article 230.6, what is the maximum length of RMC allowed to enclose service entrance conductors INSIDE the building before reaching the service disconnecting means?
- A6 feet
- B3 feet
- C10 feet
- D5 feet
Show answer & explanationAnswer & explanation
Correct answer: C. 10 feet
NEC Article 230.6 states that service-entrance conductors are considered outside of a building where they are installed in a raceway that is encased in not less than 2 inches of concrete or brick, or are installed in a raceway that is not more than 10 feet in length and enclosed by a wall or ceiling. Therefore, 10 feet is the maximum length permitted.
Why the other options are wrong
- A. Incorrect. 6 feet is too short; the NEC allows for a longer run under specific conditions.
- B. Incorrect. 3 feet is too short; the NEC allows for a longer run under specific conditions.
- D. Incorrect. 5 feet is too short; the NEC allows for a longer run under specific conditions.
Service Conductor Entry Length
The NEC limits how far service entrance conductors can run inside a building before terminating at the service disconnecting means, to minimize fire risk from unprotected conductors.
- NEC 230.6 defines conditions under which service conductors are considered 'outside' a building.
- One condition allows for up to 10 feet of raceway-enclosed service conductors within a wall or ceiling.
- This rule ensures that overcurrent protection is installed as close as practicable to the point of entry.
Memory trick: Ten feet in the wall, or concrete for all!