Additional Grounding Electrodes at Subpanel

[M. D.]

Isn't the electrode bonded if the feeder equipment grd. cond. is used?

I think it is a bonding jumper ?? would it be any more bonded if there were a seperate conductor run ? If it were a seperate conductor it can't terminate on the grounded terminal buss? it has to run to the other electrodes ??

How about ,...cut the damned thing off flush with the floor and make like you never saw it :grin: :grin:

 

[M. D.]

If this were a remote building and an electrode were required and an equipment grounding conductor run with the feeders wouldn't the equipment ground run with the feeder bond the electrode at the seperate structure to the electrode(s) at the main structure?

 

[wwhitney]

I disagree. If the EGC for the feeder begins in the service, then it is not a bonding jumper (as governed by 250.53(C)); it is a GEC (as governed by 250.64). Therefore, it must abide by 250.64(C), it must be continuous.

Hi George,

My understanding is one GEC per service. For example (2002 NEC), 250.24(A) says that the premises wiring system shall have "a" GEC, and the text frequently speaks of "the" GEC at a service. So I would say that only one of the conductors in the GES has to meet the GEC requirements of 250.64 and the others are bonding jumpers that need only meet 250.53(C). Furthermore, I would suggest that GES bonding jumpers need not always terminate at a grounding electrode. For example, in the case of a metal underground water pipe, 250.53(D)(2) specifcally allows the bonding jumper for the required supplemental electrode to terminate at the nonflexible grounded service raceway or any grounded service enclosure.

250.64 versus 250.53(C) issues aside, is there any reason a single conductor can't serve as both a feeder EGC and a GES bonding jumper? Is there any safety issue? It seems like there isn't, as a feeder EGC is utilized only in a ground fault, and the GES bonding jumper would only be utilized during an accidental overvoltage (e.g. lightning strike).

Thanks, Wayne

 

[sandsnow]

MD probably has the best answer: Cut it off flush!!!

Here is the informal NFPA interp. I got:
http://forums.mikeholt.com/showthread.php?t=81654&highlight=NFPA

It would seem that a seperate bonding jumper would be needed to connect the remote electrode back to the GES. The feeder EGC is not permitted.

I know it's an informal interp., but I would guess it's pretty close to the real deal. Maybe someone will do a proposal on this subject next cycle to get an official answer.

 

[George Stolz]

My understanding is one GEC per service. For example (2002 NEC), 250.24(A) says that the premises wiring system shall have "a" GEC, and the text frequently speaks of "the" GEC at a service. So I would say that only one of the conductors in the GES has to meet the GEC requirements of 250.64 and the others are bonding jumpers that need only meet 250.53(C).

I disagree. Look at 250.64(F) (I work off the 2005):

(F) To Electrode(s). A grounding electrode conductor shall be permitted to be run to any convenient grounding electrode available in the grounding electrode system, or to one or more grounding electrode(s) individually, or to the aluminum or copper busbar as permitted in 250.64(C). The grounding electrode conductor shall be sized for the largest grounding electrode conductor required among all the electrodes connected to it.

The text highlighted above states that there can be several GECs running to several electrodes. The use of the singular form in other sections is still grammatically correct in this case, because the rules apply to each GEC. When I say "one can expect to get wet standing in the rain" that means everyone can expect to get wet in the rain - I'm just talking to a large group of people using the singular form.

Furthermore, I would suggest that GES bonding jumpers need not always terminate at a grounding electrode. For example, in the case of a metal underground water pipe, 250.53(D)(2) specifcally allows the bonding jumper for the required supplemental electrode to terminate at the nonflexible grounded service raceway or any grounded service enclosure.

That's a good point - in my brief look just now, I couldn't find anything really describing where a bonding jumper begins and ends.

250.64 versus 250.53(C) issues aside, is there any reason a single conductor can't serve as both a feeder EGC and a GES bonding jumper?

I'd worry about the effects of encouraging lightning to an electrode at a subpanel deeper into the premises wiring. I imagine that's the reason why the GES is associated with the service, instead of being anywhere. That's just a thought, though, nothing really to back that up.

It's cool that you've put so much thought into this, Wayne.

 

[wwhitney]

I disagree. Look at 250.64(F) (I work off the 2005):

(F) To Electrode(s). A grounding electrode conductor shall be permitted to be run to any convenient grounding electrode available in the grounding electrode system, or to one or more grounding electrode(s) individually, or to the aluminum or copper busbar as permitted in 250.64(C). The grounding electrode conductor shall be sized for the largest grounding electrode conductor required among all the electrodes connected to it.

The text highlighted above states that there can be several GECs running to several electrodes.

Reading this, I have no idea what "individually" means. In any event, 250.64(F) uses the "shall be permitted" language, so it is not imposing a requirement, it is weakening one. Can you point to a code section that requires more than one GEC? Or that requires all conductors in the GES terminating at the service grounded conductor to be a GEC? What do you think about the use of the definite article in the definition of Grounding Electrode Conductor in Article 100?

It's cool that you've put so much thought into this, Wayne.

Hmm, I'm not sure my colleagues would agree with you. :smile:

Cheers, Wayne

 

[George Stolz]

Okay, I have a conductor running from the service to the water pipe, and then a conductor running to the CEE from the service.

Which is a GEC and which isn't, by this way of thinking?

 

[wwhitney]

Okay, I have a conductor running from the service to the water pipe, and then a conductor running to the CEE from the service. Which is a GEC and which isn't, by this way of thinking?

My reading of 250.64 is that one of these two conductors must be continuous as per 250.64(C). That one is the GEC. The other one need not be continuous, as it is a bonding jumper. If they are both continuous, it doesn't matter what you call them. :smile:

Cheers, Wayne

 

[George Stolz]

Let me back up a bit.

Reading this, I have no idea what "individually" means.

What else can it mean, aside from multiple GECs? This is important, because it's not just a "the/a vs. them/some" singular/plural use of language - it is a specific and deliberate concept they are trying to communicate to the user of the code.

In any event, 250.64(F) uses the "shall be permitted" language, so it is not imposing a requirement, it is weakening one.

I see it as a sort of guarantee. The presence of "shall be permitted" language is not saying that it's lessening another rule; it's just saying that of the multitude of different ways of getting the job done, this handful shall not be questioned.

Can you point to a code section that requires more than one GEC? Or that requires all conductors in the GES terminating at the service grounded conductor to be a GEC?

What I look to is 250.53(C):

250.53(C) Bonding Jumper. The bonding jumper(s) used to connect the grounding electrodes together to form the grounding electrode system shall...

I read this to state that if a conductor starts and ends at an electrode, it is a bonding jumper.

What do you think about the use of the definite article in the definition of Grounding Electrode Conductor in Article 100?

I think the same as the definition of EGC just above it. I know there can be more than one EGC. One is the minimum, but I can add to that if I desire and it still must conform to the rules governing EGCs if I would like to use it as such.

The definition of GEC is consistent with the "service on one end, GE on the other" concept, IMO. I think it's also consistent with what I remember seeing of handbook diagrams as well.

So, I'm losing track - are we being purely rhetorical here, or have you actually broken a conductor that starts at the service, ends at a GE, and called it a bonding jumper and had it approved? I don't mind either way, just curious.

 

[wwhitney]

George, I appreciate your going through the logic with me on this one. Let me first go back to your example of a water pipe electrode and a CEE. Let's say the conductor between the water pipe electrode and the service neutral bar is unspliced, so it is the GEC.

Now consider connecting a spliced conductor from the CEE in three different places: the water pipe electrode, the GEC, or the service neutral bar. Your interpretation would prohibit the last of these three locations. But why should terminating this conductor at the service neutral bar be any worse that terminating it at one of the other two locations?

Note that in this specific case, 250.53(D)(2) specifically allows the electrode supplemental to a water pipe electrode to be bonded at the service neutral bar, but that's not really the point. If you like, replace the water pipe electrode with a driven ground rod.

250.53(C) Bonding Jumper. The bonding jumper(s) used to connect the grounding electrodes together to form the grounding electrode system shall...

I read this to state that if a conductor starts and ends at an electrode, it is a bonding jumper.

Just because a conductor is used to connect grounding electrodes together doesn't mean that it will terminate at both ends at a grounding electrode. For example, since splices are allowed in bonding jumpers, one end could terminate at a splice. Also, couldn't one end of the bonding jumper terminate at the GEC? In that sense, a bonding jumper terminating at the service neutral bar where the GEC terminates is spliced to the GEC by the service neutral bar.

So, I'm losing track - are we being purely rhetorical here, or have you actually broken a conductor that starts at the service, ends at a GE, and called it a bonding jumper and had it approved? I don't mind either way, just curious.

Primarily rhetorical. What has been approved is the situation I originally described, where a secondary CEE is bonded to a subpanel ground bar, which is of course bonded by the feeder EGC to the service neutral bar. You raised the idea that considering the feeder EGC as part of a bonding jumper wouldn't fly since the feeder EGC doesn't terminate at another electrode.

Cheers, Wayne