2005 NEC 250.30(A)(4)(c)

[sowega]

Sorry I don't have the 08 code with me but I believe the code references are the same from 05 to 08 for this question.

I would like to know whether the following installation meets code with regards to the common grounding electrode conductor having a splice or joint:

I have a 3 story building with electrical rooms stacked directly on top of one another. The service equipment and grounding electrode system is on the first floor. I have a common grounding electrode originating at the the electrode system and terminating on a copper busbar (2"x4") with a listed connection (lug) in the electrical room on the second floor. Then each of the transformers on the second floor have a tap conductor that is connected to the busbar with a listed connection.

Here is the question:
Can I then connect the third floor busbar to the common grounding electrode conductor by extending it with lugs at the second floor busbar and terminating with lugs at the third floor busbar. Or would this violate the last sentence of 250.30(A)(4)(c)? Basically would lugging the common grounding electrode conductor on a busbar be considered a splice or joint?

TIA

 

[chris kennedy]

Can I then connect the third floor busbar to the common grounding electrode conductor by extending it with lugs at the second floor busbar and terminating with lugs at the third floor busbar. Or would this violate the last sentence of 250.30(A)(4)(c)? Basically would lugging the common grounding electrode conductor on a busbar be considered a splice or joint?

Your tapping to a bus, your not touching the common GEC.

 

[mcclary's electrical]

Sorry I don't have the 08 code with me but I believe the code references are the same from 05 to 08 for this question.

I would like to know whether the following installation meets code with regards to the common grounding electrode conductor having a splice or joint:

I have a 3 story building with electrical rooms stacked directly on top of one another. The service equipment and grounding electrode system is on the first floor. I have a common grounding electrode originating at the the electrode system and terminating on a copper busbar (2"x4") with a listed connection (lug) in the electrical room on the second floor. Then each of the transformers on the second floor have a tap conductor that is connected to the busbar with a listed connection.

Here is the question:
Can I then connect the third floor busbar to the common grounding electrode conductor by extending it with lugs at the second floor busbar and terminating with lugs at the third floor busbar. Or would this violate the last sentence of 250.30(A)(4)(c)? Basically would lugging the common grounding electrode conductor on a busbar be considered a splice or joint?

TIA

Is the bus continuous betwenn the first and second floor? but not the second and third?

 

[sowega]

From the two responses thus far maybe I didn't phrase the question very well.

If I'm taking a common grounding electrode from the grounding electrode system at the service entrance to the third floor electrical room but want to "stop off" at the second floor electrical room does the common electrode have to be continuous all the way to the third floor or can it be lugged and terminated on the 2nd floor busbar and then started again under another lug and extended to the 3rd floor busbar?

I'm trying to determine if terminating the common electrode under a lug on a busbar and then starting again under a different lug on the same busbar would be considered as a splice or joint.

BTW, the busbar I'm describing would be similar to a telecomm room ground bar (ie. 4"x6" copper bar with lug holes, mounted to a piece of plywood with insulated stand-offs).

My response to the first reply is that the common electrode and the transformer electrode don't have to physically touch one another. They could both terminate on a busbar per 250.30(A)(4)(c)(2).

 

[benaround]

I'm trying to determine if terminating the common electrode under a lug on a busbar and then starting again under a different lug on the same busbar would be considered as a splice or joint.



QUOTE]

IMO, it would be a joint or a splice, if a pass-thru lug was used, imo, it would be compliant.

 

[Dennis Alwon]

Never mind.... It was answered.

 

[sowega]

Thanks benaround. I'm sure the pass thru lug option would be code compliant but after looking at different parts of 250 I'm still wondering if my idea is compliant.

For instance 250.64(C)(2) and (3) would seem to indicate that sections of busbars can be considered a grounding electrode conductor. Also 250.64(F) mentions that a grounding electrode conductor can terminate on a busbar.

Last, if you look at the 08 handbook there is an illustration of the grounding electrode system and it shows a #4 running from the electrode system to building steel under a lug. Then a #6 under a different lug from building steel to a driven ground rod. I realize building steel is an electrode and that you can connect an electrode conductor to any electrode. It just seems to me that in my example that the busbar on the second floor would be considered an electrode and that the common electrode to the third floor could attach to it.

It would be nice to read other opinions.

 

[Dennis Alwon]

The #4 going to the building steel in your example is the grounding electrode. The #4 going to the ground rod is a supplemental electrode and thus can be installed in this manner. Basically it is a jumper from the steel to the rod.

Tap conductors shall be connected to the common grounding electrode conductor in such a manner that the common grounding electrode conductor remains without a splice or joint.

Thus you must have a main grounding electrode without splice to the service entrance equipment. From there you can tap to other electrodes.

Here is a nice example. Notice the main electrode is unspliced to the water pipes.

 

[benaround]

sowega,

If you have the handbook (2005) look in 250.30, Exhibit 250.15 ?

 

[cadpoint]

sowega,

If you have the handbook (2005) look in 250.30, Exhibit 250.15 ?

For all "US" playing along at the house does it have the picture that the OP is describing ?

For the Record, I've never seen three potential conductors continual from the floors above... ((yeah; for all that's worth))

 

[sowega]

Thanks Dennis.

"Here is a nice example. Notice the main electrode is unspliced to the water pipes."

I do see that the main electrode is unspliced however per 250.64(C) the main electrode could be spliced or a joint made as permitted in (1) through (4). Obviously these exceptions aren't carried over to the common grounding electrode conductor for 250.30(A)(4). It seems odd that the main electrode can be spliced per the exceptions but a common electrode can't be.

Last question for anyone on this topic.

250.30(A)(4) doesn't indicate where the common grounding electrode conductor must originate. So if I installed a #3/0cu electrode conductor from the building steel to the point at the service equipment where the main bonding jumper is located and then in each electrical room in other floors/parts of the building originate my common grounding electrode conductor on building steel to a grounding bar where I would also connect my transformer tap conductors. Would that be code compliant?

In other words, can I originate the common grounding electrode conductor for 250.30(A)(4) at any grounding electrode provided the last sentence of 250.62(F) is met? Or does the common grounding electrode conductor have to originate in the service equipment (location of main bonding jumper)?

 

[benaround]

For all "US" playing along at the house does it have the picture that the OP is describing ?

For the Record, I've never seen three potential conductors continual from the floors above... ((yeah; for all that's worth))

Cad,

It shows a single GEC run from the water pipe up to as many floors as you wish, at each

floor it shows two transformers with thier GEC sized properly, running to the 'main' GEC and

tapped to it in a NEC compliant manner.