Journeyman Electrician Exam (NEC)Services, Feeders, and Branch CircuitsEasy
A commercial building has a 400-ampere, 208Y/120V, 3-phase, 4-wire service. The main service disconnecting means consists of six circuit breakers in a single enclosure. What is the maximum number of disconnecting means permitted for a single service?
- ATwo
- BFour
- CEight
- DSix
Show answer & explanationAnswer & explanation
Correct answer: D. Six
According to NEC 230.71(A), the service disconnecting means for each service shall consist of not more than six switches or six circuit breakers mounted in a single enclosure, in a group of separate enclosures, or in or on a switchboard or switchgear.
Why the other options are wrong
- A. This is incorrect; more than two are permitted.
- B. This is incorrect; up to six are permitted.
- C. This is incorrect; eight exceeds the maximum permitted.
Maximum Service Disconnecting Means
The service disconnecting means for each service shall consist of not more than six switches or six circuit breakers, grouped and identified.
- Applies to each service.
- Maximum of six operations to disconnect all power.
- Can be in one or multiple enclosures.
Memory trick: Six Switches Secure the Service.