Grounding electrode conductor raceway shared with branch circuit

[Danpk]

A contractor installed a new transformer. The grounding electrode conductor (GEC) is run in a 1 1/4" emt conduit. There is a box outside the room that the conductor is pulled through before the GEC gets to the transformer. Apparently, from where the GEC originates, the contractor need to retrieve a 120V ciruit. To save the time and material in running a separate conduit for the 120 V, they pulled the branch circuits thru the same GEC raceway. The prior to getting to the transformer, the contractor redirected the branch circuit. This seems odd, but I haven't found any thing in the NEC to not allow this. What is your opinion ?

 

[iwire]

Odd but as far as I know not an NEC violation or safety issue.

 

[tom baker]

But all the boxes enclosures and raceways must be bonded per 250.64(E) meaning grounding bushings and jumpers.

 

[don_resqcapt19]

But all the boxes enclosures and raceways must be bonded per 250.64(E) meaning grounding bushings and jumpers.

Tom,
I don't see any such requirement. The code section only requires that the conduit be "electrically" continuous. I don't see any requirement for anything other than standard locknuts. I am aware that the figure in the handbook says otherwise, but don't see anything in the actual code rule that would support the handbook figure.

 

[augie47]

If I may answer for Tom, in his absence, look at 250.64 (E)

 

[Dennis Alwon]

If I may answer for Tom, in his absence, look at 250.64 (E)

I have to agree with Tom & Gus

250.64(E) Enclosures for Grounding Electrode Conductors. Ferrous metal enclosures for grounding electrode conductors shall be electrically continuous from the point of attachment to cabinets or equipment to the grounding electrode and shall be securely fastened to the ground clamp or fitting. Nonferrous metal enclosures shall not be required to be electrically continuous. Ferrous metal enclosures that are not physically continuous from cabinets or equipment to the grounding electrode shall be made electrically continuous by bonding each end of the raceway or enclosure to the grounding electrode conductor. Bonding shall apply at each end and to all intervening ferrous raceways, boxes, and enclosures between the cabinets or equipment and the grounding electrode. The bonding jumper for a grounding electrode conductor raceway or cable armor shall be the same size as, or larger than, the enclosed grounding electrode conductor. Where a raceway is used as protection for a grounding electrode conductor, the installation shall comply with the requirements of the appropriate raceway article

.

 

[don_resqcapt19]

I stand by my statement.

(E) Enclosures for Grounding Electrode Conductors. Ferrous metal enclosures for grounding electrode conductors shall be electrically continuous from the point of attachment to cabinets or equipment to the grounding electrode and shall be securely fastened to the ground clamp or fitting. Nonferrous metal enclosures shall not be required to be electrically continuous. Ferrous metal enclosures that are not physically continuous from cabinets or equipment to the grounding electrode shall be made electrically continuous by bonding each end of the raceway or enclosure to the grounding electrode conductor. Bonding shall apply at each end and to all intervening ferrous raceways, boxes, and enclosures between the cabinets or equipment and the grounding electrode. The bonding jumper for a grounding electrode conductor raceway or cable armor shall be the same size as, or larger than, the enclosed grounding electrode conductor. Where a raceway is used as protection for a grounding electrode conductor, the installation shall comply with the requirements of the appropriate raceway article.

The bonding is not required if the ferrous raceway is "electrically continuous". The standard ferrous raceway installation methods make the raceway electrically continuous. The bonding is only required where there are electrical breaks in the path. The most common example would be at the grounding electrode itself.

 

[augie47]

Don, What about the part that states: "Bonding shall apply at each end and to all intervening ferrous raceways, boxes, and enclosures between the cabinets or equipment and the grounding electrode. "

 

[hurk27]

I have heard arguments on both side of this one at many IAEI meetings across the country, and while in all cases the CMP's stated the intent is to not depend upon the box connectors at cabinets and box's, the other sides will always bring up the fact that the couplings in the conduit would also have to be bonded across, as they present the same problem.

the two problems arise from the terms "physically continuous" and "electrically continuous" and with both being the requirement of bonding across for the lack of either one.

The beginning of 250.64(E) has the statement

Ferrous metal enclosures for grounding electrode conductors shall be electrically continuous from the point of attachment to cabinets or equipment to the grounding electrode

but then does a back flip and states:

Ferrous metal enclosures that are not physically continuous from cabinets or equipment to the grounding electrode shall be made electrically continuous by bonding each end of the raceway or enclosure to the grounding electrode conductor

so how do we defined "physically continuous" if it is to say any ferrous raceway that is not run as one long piece of conduit without any couplings or connections through a box, then I say that is a far stretch.

So IMO I say as per the wording Don has a case, but I also know the intent was to not depend upon the connections because of the high current that they might be subject to, same as service conductors.

 

[Dennis Alwon]

I still have not heard an explanation for this.

Bonding shall apply at each end and to all intervening ferrous raceways, boxes, and enclosures between the cabinets or equipment and the grounding electrode.

 

[hurk27]

I still have not heard an explanation for this.

Bonding shall apply at each end and to all intervening ferrous raceways, boxes, and enclosures between the cabinets or equipment and the grounding electrode.

The above in red is what I have a problem with, does this mean we are to bond across every coupling?

This goes back to what is the definition of "Ferrous metal enclosures that are not physically continuous"

 

[don_resqcapt19]

If the ferrous raceway is electrically continuous, the rest of the section does not apply. It only applies where the raceway is not electrically continuous.

(E) Enclosures for Grounding Electrode Conductors. Ferrous metal enclosures for grounding electrode conductors shall be electrically continuous from the point of attachment to cabinets or equipment to the grounding electrode and shall be securely fastened to the ground clamp or fitting. Nonferrous metal enclosures shall not be required to be electrically continuous. ...

The code rule stops at that point if you have an electrically continuous raceway. There is no need to read any more of the section as it does not apply.
As far as the CMP members stating otherwise, it doesn't mean anything unless they do it in a panel statement or in the wording of the code rule itself.

 

[sameguy]

That part is for the non continuous pipe run; bond every thing. If your pipe run with boxes, LB, what ever is wrench tight, lock nuts, hubs, make the bond.

 

[hurk27]

If the ferrous raceway is electrically continuous, the rest of the section does not apply. It only applies where the raceway is not electrically continuous.

The code rule stops at that point if you have an electrically continuous raceway. There is no need to read any more of the section as it does not apply.
As far as the CMP members stating otherwise, it doesn't mean anything unless they do it in a panel statement or in the wording of the code rule itself.

Then the section Dennis posted would only apply to Ferrous metal enclosures that are not physically continuous? meaning like if you were to protect a GEC from a panel up into the floor joist with a ferrous raceway then maybe jump through a box for what ever reason then switch to another ferrous raceway before hitting the electrode?

I can see the raceway part but why would you ever go through a un-connected box in a case like this?

 

[don_resqcapt19]

Then the section Dennis posted would only apply to Ferrous metal enclosures that are not physically continuous? meaning like if you were to protect a GEC from a panel up into the floor joist with a ferrous raceway then maybe jump through a box for what ever reason then switch to another ferrous raceway before hitting the electrode?

I can see the raceway part but why would you ever go through a un-connected box in a case like this?

I have no idea why someone might do that. I see the standard installation methods as making the ferrous raceway both electrically and physically continuous, even where there are boxes in the run. I do not see the code rule as requiring any additional bonding when the raceway is installed using the standard installation methods.

 

[tom baker]

Perhaps we need a proposal to not allow a GEC to be run in a raceway with branch circuits, similar to the 2011 change to does not allow a GEC to be used for a EGC and vice versa.

 

[George Stolz]

Off the top of my head, doesn't 250.92 make explicit reference to not using standard locknuts for bonding in certain circumstances? Doesn't the lack of similar language in the section in question mean that bonding bushings are not required to make the bond?

 

[cadpoint]

A contractor installed a new transformer. The grounding electrode conductor (GEC) is run in a 1 1/4" emt conduit.....
To save the time and material in running a separate conduit for the 120 V, they pulled the branch circuits thru the same GEC raceway. The prior to getting to the transformer, the contractor redirected the branch circuit. ...

What did the math look like with the total wire fill ?

 

[jaggedben]

For what it's worth, NEC 2011 inserts the following (red) in 250.64...

(E) ... Bonding methods in compliance with 250.92(B) for installations at service equipment locations and with 250.92(B)(2) through (B)(4) for other than service equipment locations shall apply at each end and to all intervening ferrous raceways, boxes, and enclosures between the cabinets or equipment and the grounding electrode. ...

And here are the bonding methods in 250.92. (B)(2) through (4).

(2) Connections utilizing threaded couplings or threaded hubs on enclosures if made up wrenchtight.
(3) Threadless couplings and connectors if made up tight for metal raceways and metal-clad cables.
(4) Other listed devices, such as bonding-type locknuts, bushings, or bushings with bonding jumpers.

(2) and (3) seem to leave out connections made in knockouts with locknuts, thus requiring (4). Hence the need, usually, for bonding bushings at both ends of raceways. You also need the GEC separately bonded to boxes and cabinets it runs through, unless the connections made to it are with threaded hubs.

In the solar industry, since we always have a GEC running from the array (and often over 250 volts as well) we have gotten in the habit of putting a grounding bushing on every knockout anywhere. Even if it isn't required, better to just have it there and avoid any discussion with the AHJ.

 

[jaggedben]

I stand by my statement.
The standard ferrous raceway installation methods make the raceway electrically continuous.

I think that is what's up for debate. Particularly, in NEC 2008, whether connections made at knockouts with locknuts create electrical continuity. In NEC 2011 you need a bonding bushing.