NEC 250.32 (B)(1) Exception allows using grounded conductor as EGC on a separate building if the listed conditions are met. This allows not running EGC to the separate building. This also allows the grounded conductor to be bonded to the separate building's disconnect enclosure. I guess I MUST do that since the grounded conductor is the only return path. Is there any benefit of being able to bond the grounded conductor to the separate building's disconnect enclosure? Other than saving money by not running EGC, is there any benefit this exception provides? (BTW, I'm aware that this exception applies only to existing installations)
using grounded conductor as EGC on a separate building
- Thread starter unsaint34
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texie
Senior Member
- Location
- Fort Collins, Colorado
- Occupation
- Electrician, Contractor, Inspector
In my view this exception was made to accomodate doing electrical modifications to existing buildings that were served under the pre 2008 NEC rules. Keep in mind, that the old method for feeders to separate buildings was done since dirt was invented, so there are a lot of installations out there under the pre 2008 rules.
texie
Senior Member
- Location
- Fort Collins, Colorado
- Occupation
- Electrician, Contractor, Inspector
Yes, because under the old rules, in the absence of an EGC, without bonding the neutral you would have no fault return path. Conversely, with the new rules, with an EGC, you must not bond as then the EGC and the neutral would be in parallel. Either way, you still need a GES.
kwired
Electron manager
- Location
- NE Nebraska
- Occupation
- EC
I think the main reason to have separate EGC is because if the grounded conductor is used for equipment grounding, all of the EGC's and anything else bonded to them whether intentional or not, will be raised to a voltage above earth that is equal to whatever voltage drop is present on the grounded conductor. A grounding electrode will only correct this voltage for a small area around the electrode.
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