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Grounding 400a service to 2-200a panels

2K views 14 replies 7 participants last post by  frenchelectrican 
#1 ·
I have a grounding question. I am installing 400a service to my new home. We ran 350MCM wire underground thru 3" conduit from the 2ndary terminal (moped) to the house into a 320A Cooper B-Line meter. From the meter we ran 2 sets of 4/0-4/0-2/0 thru the wall to 2-200a breaker panels ("standard practice", according to my electrical supplier). The ground wire (#4Cu bare) from the grounding rods comes up from the ground and we're curious if there has to be a special splice connecting the ground wire to each breaker panel or can we run thru one breaker panel to then next, say by connecting the ground wire to a ground bus on one panel and running that thru to the next with #4Cu bare or #6Cu in conductor. Different electricians are suggesting different methods and the electrical inspector is unsure, but seems to be leaning towards the "special splice". Any feedback would be appreciated.
 
#8 ·
Kingb said:
Fascinating question. Which would YOU suggest? That would be most helpful, thanks for your input!
You don't seem to understand. You cannot CHOOSE which version you use, your state/community chooses for you. You need to find out which code cycle your area is under.
 
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#2 ·
You can do it one of 2 ways.

Take a #6 (#4 since you have it already) from one panel through each rod, then do the same for the other panel (use one clamp for each connection unless listed for multiple) or take a #6 through each rod to the first panel and a #4 jumper from panel to panel.

The connection should be made as close as possible to the grounded conductor. Some panels have a lug where the neutral connects to terminate the GEC. If not, I usually terminate on the neutral bar just below where the neutral connects.

Keep in mind, if you think about putting multiple wires under one lug because it fits, make sure that the lug is listed for multiple connections. Usually it isn't.
 
#5 ·
I have a grounding question. I am installing 400a service to my new home. We ran 350MCM wire underground thru 3" conduit from the 2ndary terminal (moped) to the house into a 320A Cooper B-Line meter. From the meter we ran 2 sets of 4/0-4/0-2/0 thru the wall to 2-200a breaker panels ("standard practice", according to my electrical supplier). The ground wire (#4Cu bare) from the grounding rods comes up from the ground and we're curious if there has to be a special splice connecting the ground wire to each breaker panel or can we run thru one breaker panel to then next, say by connecting the ground wire to a ground bus on one panel and running that thru to the next with #4Cu bare or #6Cu in conductor. Different electricians are suggesting different methods and the electrical inspector is unsure, but seems to be leaning towards the "special splice". Any feedback would be appreciated.
What NEC are you using?
 
#6 ·
We run the water ground to one panel, the ground rods to the other, run a jumper between the two panels, and split bolt the jumper and each of the grounds above the panels.
 
#9 ·
Kingb said:
Fascinating question. Which would YOU suggest? That would be most helpful, thanks for your input!
The version adopted by your governing body.
 
#12 ·
I've seen a couple posts from people in that area stating the same thing. It may be some sort of local thing.
 
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