Electrician Red Seal · Question
An electrician is installing a 3-wire, 120/240 V feeder supplying a subpanel in a detached garage, which contains only 120 V loads. The main service is a 4-wire, 120/240 V system with a grounded neutral. What is the correct method for connecting the neutral and grounding conductors at the detached garage subpanel according to the CEC?
Rule 10-208(b) of the CEC requires that for a feeder supplying a detached building from a main service that is a 4-wire system with a grounded neutral, the neut
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Question: An electrician is installing a 3-wire, 120/240 V feeder supplying a subpanel in a detached garage, which contains only 120 V loads. The main service is a 4-wire, 120/240 V system with a grounded neutral. What is the correct method for connecting the neutral and grounding conductors at the detached garage subpanel according to the CEC?
Answer options:
- Bond the neutral bus to the enclosure and install a separate grounding electrode.
- Isolate the neutral bus from the enclosure and bond the neutral to the grounding electrode. ✅ Isolate the neutral bus from the enclosure and bond the grounding conductor to the enclosure, with a separate grounding electrode.
- Bond both the neutral bus and the grounding conductor to the enclosure, with a separate grounding electrode.
Correct answer: Isolate the neutral bus from the enclosure and bond the grounding conductor to the enclosure, with a separate grounding electrode.
Explanation: Rule 10-208(b) of the CEC requires that for a feeder supplying a detached building from a main service that is a 4-wire system with a grounded neutral, the neutral conductor must be isolated from the enclosure at the subpanel. The equipment grounding conductor must be bonded to the enclosure, and a separate grounding electrode must be installed at the detached building and bonded to the enclosure. This prevents parallel paths for neutral current on the grounding system.
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