CSLB C-10 Electrical ContractorWiring Methods and MaterialsMedium
A contractor installs Type SE cable as a feeder from the main service panel to a detached garage subpanel. Which of the following wiring requirements applies to this installation?
- AThe SE cable's neutral conductor may serve as both the neutral and the equipment ground at the subpanel
- BA separate equipment grounding conductor must be provided since the neutral cannot be used for grounding beyond the service
- CSE cable is prohibited for use as a feeder under any circumstances
- DNo grounding electrode conductor is required at the detached structure
Show answer & explanationAnswer & explanation
Correct answer: B. A separate equipment grounding conductor must be provided since the neutral cannot be used for grounding beyond the service
Per NEC 225.30 and 250.32, feeders to separate structures must have an equipment grounding conductor, and neutral-to-ground bonding is only permitted at the service, not at a subpanel. Therefore, SE cable used as a feeder requires an EGC separate from the neutral, and the subpanel's neutral and ground bars must remain separated.
Why the other options are wrong
- A. Combining neutral and ground beyond the service creates an objectionable current path violation.
- C. SE cable is permitted as a feeder as long as proper grounding provisions are met.
- D. A grounding electrode system is still required at the detached structure.
SE Cable as a Feeder
When SE cable feeds a subpanel, it must include a separate equipment grounding conductor because neutral-ground bonding is only allowed at the service.
- Neutral and ground must be separated at subpanels
- Feeders to separate structures need an EGC
- A grounding electrode system is still required at detached structures
Memory trick: Only the service gets to marry neutral and ground—subpanels must stay separated