GEC and H20 Bond

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ivsenroute

ivsenroute

Senior Member
Location
Florida
Here is a good one to think about.

Overhead service 120/240 to a single gang meter base. From the meter base there are two main panels. One "A" is located in the basement and the other "B" is located on the other side of the house. Immediately inside the basement where the SE comes through the wall is Panel "A" and right along side it is the disconnect for Panel "B".

There is a #4 Cu GEC coming from a CEE that ties directly to the Disco for Panel "B". From there it jumps over to Panel "A" to provide the GEC. There are 2 separate lugs on the neutral bar of the disco.

Panel "A" provides the 1/0 Cu bond to the water pipe.

Is this a legal install under the 2005 NEC?
 
I see a problem with both the #4 and the 1/0 as far as 250.64(D).
If you happen to have a '05 Handbook, Exhibit 250.26 shows a good method of connecting GEC to multiple service disconnects.
As I understand the last sentence of 250.64(D), you can tap a common GEC to multiple disconnects but you can not "loop" thru disconnects.
I would visualize the 1/o coming to one disconnect or a common point at the disconnects and a properly sized tap made to the other and the #4 tapped to the 1/0 common GEC also (or to the water pipe).
 
I'll show this one in pictures:

First the setup where the disco for panel B is on the left and Panel A is on the right.

IMG_6759.JPG



Next we see the inside of the disco for Panel B which happens to be the termination point for the GEC from the CEE

IMG_6760.JPG



Then we see the inside of Panel A which has its own disco. The H20 pipe bond only comes from this panel.

IMG_6761.JPG



Lastly, sub-feed Panel B is here and has another problem with the equipment grounding bars.

IMG_6763.JPG
 
I am not sure that 250.64(D) requires the 1/0 to hit both panels. I believe you can run the 1/0 to one panel and then jump the #4 to the second panel.

In fact, If you are using 3/0 copper then the 1/0 EGC would only need to be a #2. Table 250.66 Note 1.
 
That #4 between panels is doing the inevitable paralling of the neutral.

But, is using the disco's neutral lugs and bus to bond the panel's bus okay?
 
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