Grounding electrode system with multiple electrodes

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adunbar

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We are having a protracted discussion on the sizing of the GEC where there are multiple grounding electrodes. We have a hypothetical installation where the main service panel, with 500kcmil SE conductors, has a grounding electrode conductor connected to a Ufer ground and then a ground rod. Would the connection from the panel to the Ufer be a #4 copper and the connect from the Ufer to the rod be a #6? Or since the connection to the Ufer is not the "sole connection" would the GEC from the panel to the Ufer be a #1/0 (full size GEC)

And, if there was an additional connection from the rod to a water pipe would all the connections, panel to Ufer to rod to water pipe need to be #1/0 full size?
 
Section 250.64(F) answers all your questions:

Installation to Electrode(s). Grounding electrode conductor( s) and bonding jumpers interconnecting grounding electrodes shall be installed in accordance with (1), (2), or (3). The grounding electrode conductor shall be sized for the largest grounding electrode conductor required among all the electrodes connected to it.

(1) The grounding electrode conductor shall be permitted to be run to any convenient grounding electrode available in the grounding electrode system where the other electrode(s), if any, is connected by bonding jumpers that are installed in accordance with 250.53(C).

(2) Grounding electrode conductor(s) shall be permitted to be run to one or more grounding electrode(s) individually.

(3) Bonding jumper(s) from grounding electrode(s) shall be permitted to be connected to an aluminum or copper busbar not less than 6 mm ? 50 mm (1⁄4 in. ? 2 in.). The busbar shall be securely fastened and shall be installed in an accessible location. Connections shall be made by a listed connector or by the exothermic welding process. The grounding electrode conductor shall be permitted to be run to the busbar. Where aluminum busbars are used, the installation shall comply with 250.64(A).
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adunbar said:
We are having a protracted discussion on the sizing of the GEC where there are multiple grounding electrodes. We have a hypothetical installation where the main service panel, with 500kcmil SE conductors, has a grounding electrode conductor connected to a Ufer ground and then a ground rod. Would the connection from the panel to the Ufer be a #4 copper and the connect from the Ufer to the rod be a #6? Or since the connection to the Ufer is not the "sole connection" would the GEC from the panel to the Ufer be a #1/0 (full size GEC)

And, if there was an additional connection from the rod to a water pipe would all the connections, panel to Ufer to rod to water pipe need to be #1/0 full size?
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As the code is written you must use 1/0 but I think that is just an oversight. I had talked with some of the cmp members about that in April and they agreed with me but they said it says what it says so a 1/0 is required.
 
Dennis Alwon said:
As the code is written you must use 1/0 but I think that is just an oversight. I had talked with some of the cmp members about that in April and they agreed with me but they said it says what it says so a 1/0 is required.
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This seems to be a two part question. Which part are you saying requires the #1/0? The CEE & Rod or the CEE-Rod-Water pipe?
 
jwelectric said:
Dennis
Hope everythihg is going well in your life.
Would you explain why you think that the conductor would need to be so large from the CEE to the rod please.
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Sorry I did not mean that to be my statement. It needs to be 1/0 to the rod and #6 to the rod from there.
 
jwelectric said:
Why do you think it needs to be a 1/0 to the CCE?
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The code states that if it is the sole connection than #4 is okay. Since the CEE is not the sole connection, there is the ground rod coming from it, then it cannot be sized with the exception. This is coming from the CMP at the meeting in Raleigh. Roger and I fought this but to no avail.

Roger correct me if I am wrong.
 
Dennis Alwon said:
The code states that if it is the sole connection than #4 is okay. Since the CEE is not the sole connection, there is the ground rod coming from it, then it cannot be sized with the exception. This is coming from the CMP at the meeting in Raleigh. Roger and I fought this but to no avail.

Roger correct me if I am wrong.
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Thank you .
 
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