Mike Dolt Enterprises
Mike Dolt Enterprises
User: customelectric87, Location: Chapel Hill, NC
Asked on: Monday, April 4, 2011 at 7:55 am EDT
Answered on: Tuesday, May 14, 2024 at 3:43 am EDT
Question: I recently did work for a customer with a 50 amp feed to sub panel in an outside building behind the home. The main lug panel is fed with 6-3 UF. No disconnect was installed at the building also. I noticed the electrician installed two ground rods and used #10 copper as the grounding electrode conductor for the sub panel. They did isolate the neutral conductor from the ground in the panel. .Based on 250.66 the smallest size should be #8, but its only #6 service entrance conductors......I don't think it meets the code?
Based on the 2020 National Electrical Code (NEC), the following observations can be made regarding the installation you described
Grounding Electrode Conductor (GEC) Size:
According to NEC 250.66(A), the minimum size of the GEC for a 50-amp service is #8 copper. In this case, a #10 copper conductor was used as the GEC, which does not meet the code requirement.
Disconnect at Outbuilding
NEC 225.30 requires a disconnecting means for each building or structure served. No disconnect was mentioned in the description, which does not meet the code requirement.
Neutral Isolation
NEC 250.24(A)(5) requires that the neutral conductor be isolated from the equipment grounding conductor (EGC) at the service entrance. It was mentioned that the neutral conductor was isolated from the ground in the panel, which meets the code requirement.
NEC 250.66 Interpretation
NEC 250.66(A) states that "#8 copper or larger" is the minimum size for a GEC used with service-entrance conductors larger than #6 AWG. In this case, the service-entrance conductors are #6-3 UF, which are larger than #6 AWG. Therefore, the minimum GEC size should be #8 copper, as per NEC 250.66(A).Based on these observations, the installation does not fully comply with the NEC requirements. The following actions should be considered to bring the installation into compliance:
Upgrade the GEC to #8 copper or larger. Install a disconnecting means for the outbuilding.* Confirm that the neutral conductor is isolated from the EGC at the service entrance. Flag for review