grounding electrode conductor 2008 nec

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grumpy11

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the job is to install a 100amp feeder from a service switch to feed a 75kva transformer.

hence the building is an all concrete building. the question is can i install the gec in the same conduit with the feed conductors
 
Is it a building with multiple transformer installations where 250.30(A)(4) would apply ? or a reason where you can not establish one of the 250.30(A)(7) electrodes at the transformer ?
 
in this town i need to go to steel or water main .in this installation i want to pick up the gec within a service board where im adding a service switch to feed a transformer.

i think that article 230.7 exception would apply.

service switch to transformer
 
NEC 2011

When I apply 250.30 (A)(4), it seems to me, that the seperately derived system location dictates the routing of the Grounding Electrode Conductor. So the transformer location is done with grounding (Earthing) in mind.

That being said, to me the routing you describe depends on the layout and latitude of the inspector. Also, the GEC would have to be insulated in this case?
 
dare I ask again..is this a building with multiple transformers ?
 
yes it is but there is no gec riser transformer are grounded to rod in deck rod is not grounded.buliding went up in 1968 worked on it first day in business long time ago.

transformers have been grounded incorrectly for years

this new transformer is for one tenant only.
 
Wow. That is a sticky situation.
I understand the reference to 230.7 but the only service conductors would be to the primary of the service disconnect so 230.** would be irrelevant for your transformer feeder and secondary.
That said, at the moment, I don't have a suggestion.
 
yes as you get into it more its not clear. but i read a post to mike holt that some guy wanted to do the same thing on a boat dock transformer feed from a service switch

the answer was 230.7 exception 1.
 
grumpy11 said:
yes as you get into it more its not clear. but i read a post to mike holt that some guy wanted to do the same thing on a boat dock transformer feed from a service switch

the answer was 230.7 exception 1.
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I do not see a problem as long as the conduit is continuious and you follow 250.64 (E) and bond the GEC at both ends.
 
good point .i wish i knew how to send a little drawing with this thread but i don't so lets see how i do with explaining it.

service board board. tapping a new service switch 100 amp ct cabinet (480 VOLT) FEEDER UP TO PRIMARY SIDE DISCONNECT FOR TRANSFORMER feeder calls for 4#1 plus 1#6 egc.

now if i install the #2 gec along with the feeder in emt yes 250.64 (e) must be used. now i wanted to pick up the gec in the service board. . i know buy using migb i could bond the emt to the gec. but now i would be running the gec through the service to the new service switch through the ct cabinet through the primary disconnect to the transformer.and just bond the egc to the enclosures. seems like to many enclosures running the gec through.

another thought would be is to install a pull box after the ct cabinet do all the wiring without the gec going through the switch and cabinet then run the gec in it own conduit to the pull box install with feeder then at the primary disconnect install pull box intercept the gec at pull box and go to transformer.
 
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