- Location
- Illinois
- Occupation
- retired electrician
Re: Grounding of residential subpanel
pb,
I think that, if I were the AHJ, I'd permit a remote EGC for a feeder with a 70 amp OCPD. I don't think that the additional impedance caused by the fault clearing path being remote from the feeder will have any great effect on the fault clearing time of this circuit. If the circuit OCPD was larger, over 200 or 300 amps, I would not approve the remote EGC.
As far as the hazard level, of this installation there is a potential for harm. This is not much different from the 3 wire circuits that were permitted for many years on stove and dryer branch circuits. In these circuits a single conductor served as both the grounded and grounding conductor. There were proposals made over 3 or 4 code cycles before the rule was changed to require 4 wire circuits. All of the proposals cited the "potential" problems that could occur when using a single conductor for both functions. The CMP asked for any evidence of a problem that had really occurred. I don't recall anyone citing an actual real world problem that was caused because of the use of a 3 wire circuit.
Don
pb,
I think that, if I were the AHJ, I'd permit a remote EGC for a feeder with a 70 amp OCPD. I don't think that the additional impedance caused by the fault clearing path being remote from the feeder will have any great effect on the fault clearing time of this circuit. If the circuit OCPD was larger, over 200 or 300 amps, I would not approve the remote EGC.
As far as the hazard level, of this installation there is a potential for harm. This is not much different from the 3 wire circuits that were permitted for many years on stove and dryer branch circuits. In these circuits a single conductor served as both the grounded and grounding conductor. There were proposals made over 3 or 4 code cycles before the rule was changed to require 4 wire circuits. All of the proposals cited the "potential" problems that could occur when using a single conductor for both functions. The CMP asked for any evidence of a problem that had really occurred. I don't recall anyone citing an actual real world problem that was caused because of the use of a 3 wire circuit.
Don