CSLB C-10 Electrical ContractorEquipment and InstallationHard
A commercial building has a 400A, 208Y/120V service. The design calls for six individual circuit breakers, each rated at various ampacities, mounted together in one panelboard enclosure to serve as the building's service disconnecting means, with no single main breaker. Is this arrangement permitted under the CEC?
- AYes, but only if each breaker is rated identically
- BNo, more than two service disconnects are never allowed
- CYes, up to six disconnects grouped together are permitted as the service disconnecting means
- DNo, a service must always have a single main disconnect breaker
Show answer & explanationAnswer & explanation
Correct answer: C. Yes, up to six disconnects grouped together are permitted as the service disconnecting means
NEC 230.71 permits the service disconnecting means to consist of not more than six switches or six circuit breakers grouped in a single enclosure or in a group of separate enclosures, without requiring a single main disconnect ahead of them.
Why the other options are wrong
- A. Individual breaker ampere ratings within the six do not need to match each other.
- B. Up to six service disconnects are explicitly permitted, not limited to two.
- D. A single main disconnect is not mandatory; the code allows up to six disconnects in lieu of one main.
Six Disconnect Rule
NEC 230.71 allows the service disconnecting means to be composed of up to six switches or breakers grouped together, instead of a single main disconnect.
- Maximum of six switches or breakers total
- Must be grouped (same location) and each marked to indicate its purpose
- Applies to overall service, not each individual panel
Memory trick: Six switches can stand in for one big main.