250.30(7)Exception No.2 Is this Exception saying if you were to have a transformer being fed out of a swithch gear or similar service equipment. You can size your primary feeder ground to 250.66 and use it as a grounding electrode. any Input on this topic would be greatly appreciated.
Ground a separately derived ac system
- Thread starter shaw0486
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crossman
Senior Member
- Location
- Southeast Texas
(NEC 2005) I don't think it means that. What it says is that the service grounding electrode can be used as the SDS grounding electrode. The SDS will still require a seperate GEC. IMO you can't use the feeder equipment grounding conductor for this connection, even if it is sized per 250.66.
- Location
- Illinois
- Occupation
- retired electrician
I see no reason why the primary EGC, sized per 250.66 cannot be used as the grounding electrode conductor for the SDS.
Don
Don
crossman
Senior Member
- Location
- Southeast Texas
I'm still thinking. If the primary feeder EGC can be used as a SDS GEC, then the corollary is that the SDS GEC can be used as the primary feeder EGC. It would have to go both ways. Not sure that means anything.
Now, the SDS GEC would have to comply with 250.64 most notably (C) and (F) and I'm not sure that could be accomplished under normal conditions with the feeder EGC.
Not sure, but I can't see the intent to let an EGC from one system and a GEC from another system be the same conductor.
Now, the SDS GEC would have to comply with 250.64 most notably (C) and (F) and I'm not sure that could be accomplished under normal conditions with the feeder EGC.
Not sure, but I can't see the intent to let an EGC from one system and a GEC from another system be the same conductor.
LarryFine
Master Electrician Electric Contractor Richmond VA
- Location
- Henrico County, VA
- Occupation
- Electrical Contractor
Can you find a prohibition?crossman said:
crossman
Senior Member
- Location
- Southeast Texas
2008 NEC 250.64(C)
The SDS GEC needs to be run from the Grounding Electrode all the way to the SDS in one continuous length without splice or joint unless spliced by irreversible compression splices or exothermic welding. This could not be accomplished under normal circumstances if we used the feeder EGC as the SDS GEC.
I can visualize taking an unspliced GEC from the electrode, through the feeder disconnect, in the feeder conduit, then directly to XO. This would meet the requirements of 250.64. Now, to use it as the feeder EGC, we tap onto the GEC in the feeder disconnect and attach it to the disconnect ground bar, and we could do the same in the transformer, or we could rely on the System Bonding Jumper to complete the connection to the xfmr case. Now, the one grounding conductor is being used both as the feeder EGC and as the SDS GEC.
Somehow, I just don't see this as being the intent of 250.30(7)
The SDS GEC needs to be run from the Grounding Electrode all the way to the SDS in one continuous length without splice or joint unless spliced by irreversible compression splices or exothermic welding. This could not be accomplished under normal circumstances if we used the feeder EGC as the SDS GEC.
I can visualize taking an unspliced GEC from the electrode, through the feeder disconnect, in the feeder conduit, then directly to XO. This would meet the requirements of 250.64. Now, to use it as the feeder EGC, we tap onto the GEC in the feeder disconnect and attach it to the disconnect ground bar, and we could do the same in the transformer, or we could rely on the System Bonding Jumper to complete the connection to the xfmr case. Now, the one grounding conductor is being used both as the feeder EGC and as the SDS GEC.
Somehow, I just don't see this as being the intent of 250.30(7)
crossman
Senior Member
- Location
- Southeast Texas
Here is a diagram of the situation which in my opinion would be a violation.
jcross
Member
- Location
- Piney Flats, TN
Question
Question
Does the GEC need to be bonded to both ends of the ferrous raceway it is installed in? NEC 250.64(E)?
Question
Does the GEC need to be bonded to both ends of the ferrous raceway it is installed in? NEC 250.64(E)?
- Location
- Illinois
- Occupation
- retired electrician
Crossman,
Yes, your drawing is shows a violation, however if the GEC from the transformer is run through the service panel and connected to the grounding electrode, a tap is made to the equipment grounding bar in the service panel, and in the case of ferrous raceways, both ends of the raceway are bonded to the GEC, the installation would be in compliance.
Yes, your drawing is shows a violation, however if the GEC from the transformer is run through the service panel and connected to the grounding electrode, a tap is made to the equipment grounding bar in the service panel, and in the case of ferrous raceways, both ends of the raceway are bonded to the GEC, the installation would be in compliance.
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