Grounging Electrode Conductor

[rt]

I have a 240/120 200A split neutral Square D load center. The grounding electrode conductor is connected to the equipment ground bus. Also, there is no main bonding jumper. Besides being a Code violation, what problems might I see from this?

 

[al hildenbrand]

Re: Grounging Electrode Conductor

Is the service disconnect in this load center?

 

[rt]

Re: Grounging Electrode Conductor

Yes, the service disconnect is in the load center.

 

[al hildenbrand]

Re: Grounging Electrode Conductor

A lot depends on the nature of the grounding electrode system in the occupancy that the load center is in.

Ideally, a ground fault between a hot branch circuit conductor and something connected to an equipment grounding conductor will achieve a large fault current that quickly engages the overcurrent protective device.

The fault current is coming from the power company transformer, and is returning to it.

Without the main bonding jumper, the fault current will not see the service entrance grounded conductor path back to the transformer.

Now, to be careful in my statement, the actual path(s) the return current at your load center will have is heavily influenced by the materials used to construct the electrical system and the occupancy.

 

[luke warmwater]

Re: Grounging Electrode Conductor

Are you absolutely sure that there is not even a bonding screw through the neutral bar into the can?

You might not actually have a jumper directly connected from the neutral bar to the grounding bar.

 

[rt]

Re: Grounging Electrode Conductor

There is a bonding screw through the neutral bar. There is not a jumper between the neutral lugs and equipment gounding lugs. Continuity between the neutral bus and equipment ground is established through the box.

 

[al hildenbrand]

Re: Grounging Electrode Conductor

As I recall, SqD calls out on the label inside the load center, the specific lugs that one can use on the neutral bar to land the GEC.

I don't recall the SqD label calling out alternative locations that includes equipment ground bars. So, a manufacturer instruction problem is an additional problem you might see. The worst case will be a sharp insurance investigator catching the assembly error (by manufacturer's instructions) at some distant point in time following a catastrophic event that includes, in some manner, the electrical system.

I've seen an insurance investigator cut out, intact, the entire load center and wiring harness out to 20' from the panel, and take it to store as material evidence for a case that the insurance company was developing against an electrician for work that was done fifteen (15) years ago. I was hired to replace the load center and branch circuit homeruns in this particular case.

 

[luke warmwater]

Re: Grounging Electrode Conductor

Originally posted by rt:
There is a bonding screw through the neutral bar. There is not a jumper between the neutral lugs and equipment gounding lugs. Continuity between the neutral bus and equipment ground is established through the box.

I fail to see a Code violation.

 

[al hildenbrand]

Re: Grounging Electrode Conductor

Wouldn't that be 110.3(B)?

 

[luke warmwater]

Re: Grounging Electrode Conductor

I don't know.

I don't use Sq. D, and there was no model # given.

So, without more info on the actual panel, I cannot claim there is a violation.

It is possible.

 

[al hildenbrand]

Re: Grounging Electrode Conductor

So, rt, does the panel label call out the GEC location on the neutral bar?

 

[don_resqcapt19]

Re: Grounging Electrode Conductor

The code does not permit the grounding electrode conductor to be connected to the equipment grounding bus in this application. This is only permitted if the main bonding jumper is a wire or busbar. See 250.24(A).
Don

 

[hurk27]

Re: Grounging Electrode Conductor

Most Square D panels will have another lug to land the GEC in. The neutral is landed in the large lug at the top middle and has the hole for the screw for the bond to the panel Can or (MJB) in the busbar next to it, the GEC is landed in the smaller lug next to it or in ether neutral bar. Then the busbar runs to both neutral bars on each side which run down just outside of where the breakers mount. For main breaker Square D panels where use as service equipment, it is not required to install the auxiliary grounding bars when NM is used. The neutral bar can be used for this purpose and is identified in the label for such use as per 408.20 (last paragraph) But as Don pointed out the GEC must not land on this auxiliary grounding bar if it is installed because it is only connected via the MJB which is only a screw. it can land on ether neutral bar (right or left) that is connected via a busbar to the main grounded service conductor.

250.24(A)(4) Main Bonding Jumper as Wire or Bus-bar . Where the main bonding jumper specified in 250.28 is a wire or busbar and is installed from the neutral bar or bus to the equipment grounding terminal bar or bus in the service equipment, the grounding electrode conductor shall be permitted to be connected to the equipment grounding terminal bar or bus to which the main bonding jumper is connected.

But it is allowed for EGC's:

250.28(A) Material. Main bonding jumpers shall be of copper or other corrosion-resistant material. A main bonding jumper shall be a wire, bus, screw , or similar suitable conductor.

[ March 06, 2005, 02:06 AM: Message edited by: hurk27 ]

 

[luke warmwater]

Re: Grounging Electrode Conductor

I didn't see the forest for all of the trees.

I thought we were talking about using a ground bar.
So your posts confused me. After re-reading the original post, I see we are talking about landing the neutral on a seperate ground bar. Too many GEC and EGC terms.

I concur.

 

[hurk27]

Re: Grounging Electrode Conductor

By Luke: I see we are talking about landing the neutral on a separate ground bar. Too many GEC and EGC terms.

That's not what I'm getting?
What I thought the question was about the landing of the GEC on the grounding bar which if only has a screw connection to the neutral bar would be a violation as Don pointed out with 250.24(A)(4). Which If the neutral did land on the grounding bar I would think would be a violation too but the article escapes me. :roll:

 

[al hildenbrand]

Re: Grounging Electrode Conductor

Going back to rt's first post, as I paraphrase it, "Even though it is a Code violation, what problems might be caused by landing the GEC on an equipment ground bus (bolted to the service enclosure) that is bonded to the neutral only by a screw used as the main bonding jumper?"

 

[petersonra]

Re: Grounging Electrode Conductor

Originally posted by al hildenbrand:
Going back to rt's first post, as I paraphrase it, "Even though it is a Code violation, what problems might be caused by landing the GEC on an equipment ground bus (bolted to the service enclosure) that is bonded to the neutral only by a screw used as the main bonding jumper?"

Good question. Perhaps there is some tortured lgic that might explain why this is prohibited in the first place.

 

[hurk27]

Re: Grounging Electrode Conductor

I agree Al as long as the mounting screws are tight and can't work loose everything should be alright.
Now were talking about GEC's Not neutral's :roll:

[ March 07, 2005, 06:37 PM: Message edited by: hurk27 ]