We have several old schools in our district, which have panelboards distributed around the building. When the schools were built the conduit served as the equipment grounding conductor. I'm told the earth in this area of the country is rather corrosive and that the conduit may no longer be intact. I'm thinking that if I just test at the panelboards the interconnections would indicate an adequate ground, but I fear it would not be one originating at the service. Would it be adviseable to run a supplementary grounding conductor from the service, in a new conduit, to each panel? It would not be with the circuit conductors, but would guarantee an equipment grounding conductor at the panel. I appreceiate your thoughts on the matter.
Supplementary Grounding
- Thread starter wilson
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- Bremerton, Washington
Re: Supplementary Grounding
All the circuit conductors including the equipment grounding conductor have to be in the same raceway, otherwise the impedance of the circuit is too high for an effective ground fault return path. You are limited to 6 ft for an external equipment bonding jumper on the external.
All the circuit conductors including the equipment grounding conductor have to be in the same raceway, otherwise the impedance of the circuit is too high for an effective ground fault return path. You are limited to 6 ft for an external equipment bonding jumper on the external.
karl riley
Senior Member
Re: Supplementary Grounding
In an old school building the electricians had bonded neutral-ground in all subpanels. Their excuse was that they didn't trust the old conduits. However, since my measurements showed they were doing a good job of conducting neutral current back to the service, my team electrician disconnected the bonds as required by Code. The AHJ overruled this and re-established the violation. I asked him to test the conduits for continuity since I showed no problem. He refused. So that school remained in violation and high magnetic fields remained, particularly in the room for learning-impaired students. The Old Boys won out.
Karl
In an old school building the electricians had bonded neutral-ground in all subpanels. Their excuse was that they didn't trust the old conduits. However, since my measurements showed they were doing a good job of conducting neutral current back to the service, my team electrician disconnected the bonds as required by Code. The AHJ overruled this and re-established the violation. I asked him to test the conduits for continuity since I showed no problem. He refused. So that school remained in violation and high magnetic fields remained, particularly in the room for learning-impaired students. The Old Boys won out.
Karl
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