Tandem Panels

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smwilli

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So a customer had (2) 100 amp disconnects placed on the outside of his house off the meter. He has 200 amp service to the house. 1 disconnect goes to the existing 100 amp panel (done when the house was built circa 1980) He now wants another 100 amp panel installed off of the other 100 amp disconnect. What would be the proper way to ground both panels? Run 2 grounding electrode conductors to the grounding electrode, 1 from each disconnect? What about the ground to the homes water service? Thanks for all your help!
 
smwilli said:
What would be the proper way to ground both panels? Run 2 grounding electrode conductors to the grounding electrode, 1 from each disconnect? What about the ground to the homes water service? Thanks for all your help!
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smwilli welcome to the forum. Article 250.64(D) allows GEC taps to be made for multiple service equipment, but from your discription it sounds like the existing GEC is made at the indoor panel and not at the outdoor service disconnect. Article 250.24(A)1 only allows the GEC up to the service disconnect and 250.24(A)4 does'nt allow grounding the grounded service conductor past the service disconnect.IMO the GEC should be brought out to each service disconnect in accordance with 64(D). Then we could talk about the feeder conductors into the house.

Rick
 
smwilli said:
So a customer had (2) 100 amp disconnects placed on the outside of his house off the meter. He has 200 amp service to the house. 1 disconnect goes to the existing 100 amp panel (done when the house was built circa 1980) He now wants another 100 amp panel installed off of the other 100 amp disconnect. What would be the proper way to ground both panels? Run 2 grounding electrode conductors to the grounding electrode, 1 from each disconnect? What about the ground to the homes water service? Thanks for all your help!
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You need to explain this better. If there is an existing 200 amp service I would assume the GEC is taken care of when it was installed. If you add another panel ( sub panel) from the existing 100 amp service panel then you would not need to bother with a GEC just run a 4 wire cable to the panel and ground it with the grounding conductor.

Is there something I am missing? besides my hair...
 
I'll have to take a look at it and report back. I haven't actually seen it yet, just had a verbal description. Thanks for the welcome and the help!
 
smwilli said:
thats my question. Do i run a egc from each disconnect to the grounding electrodes?
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If the house has (2) 100 amp disconnects that were installed when the house was built, you are done with the grounding of the service. Now all you need to do is run your 2 phase conductors 1 neutral conductor and one ground wire, between the new panel and the existing disconnect only. You have no more need to go to the grounding electrode, that should have been done when the service was installed originally.Verify it was run and that is it.
 
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