CSLB C-10 Electrical ContractorEquipment and InstallationEasy
A commercial building has a 400-ampere, 208Y/120-volt service. The design calls for a main service disconnect and two additional individual disconnects for specific loads, each rated at 100 amperes. All disconnects are grouped in a single enclosure. Which of the following statements is true regarding the number of service disconnects allowed by the NEC?
- AThe number of disconnects is unlimited as long as they are grouped together.
- BThree disconnects are permitted, but they must be rated equally.
- COnly a single main service disconnect is allowed for a service of this size.
- DA maximum of six service disconnects are permitted for each service.
Show answer & explanationAnswer & explanation
Correct answer: D. A maximum of six service disconnects are permitted for each service.
According to NEC 230.71(A), a maximum of six disconnects are permitted for each service entrance, grouped in a single location. The provided scenario of a main disconnect and two additional disconnects totals three, which is within the six-disconnect rule.
Why the other options are wrong
- A. The number of disconnects is limited to six, not unlimited.
- B. The disconnects are not required to be rated equally, only that the sum of their ratings can meet the service requirements if not individually sized for specific loads.
- C. The NEC allows up to six disconnects, not just a single one, even for larger services, as long as they are grouped.
Six-Disconnect Rule
The NEC allows a maximum of six switches or six circuit breakers to serve as the service disconnecting means for any single service, provided they are grouped in a single location.
- Applies to service disconnecting means.
- Maximum of six disconnects.
- Must be grouped in one location.
- Found in NEC 230.71(A).
Memory trick: Six Switches Secure the Service Start.