two grounds on one rod?

[inspector_guy]

My neighbors house has a ground line (6 awg copper) from the meter and from the panel (exterior of the house) and they both clamp on to the same ground rod. Is this acceptable? It is my understanding that electricity is lazy and will always take the path of least resistance- down one grounding conductor and back up the other-or will the earth 'absorb' the power?
-Takk fra meg, Joe B.

 

[roger]

Re: two grounds on one rod?

Joe, only one of these are needed. I would look at your nieghbors panel and make sure the EGC's (grounds) and GC's (neutrals for this conversation) are landed on the same continuous bar and said bar/s is/are bonded to the can.

If this is done it is not hurting anything to leave it as is.

The only reason for this rod and connection/s is /are surge and lightining disipation.

If there is current (besides very minute amounts) flowing up one and down another in every day normal use, we have a problem.

Roger

 

[don_resqcapt19]

Re: two grounds on one rod?

The installation places the #6 conductors in parallel with the grounded conductor between the meter and the panel. A significant portion of the grounded conductor current will flow on the grounding electrode conductors.
Don

 

[roger]

Re: two grounds on one rod?

Don, grounding and bonding conductors are not direct electrical connections (per the big brains) so how can we have a problem?

We can ground a system a many times as we want upstream of the " Main"


Roger

 

[tom baker]

Re: two grounds on one rod?

this would be a violation of 250.6
"250.6 Objectionable Current over Grounding Conductors.
(A) Arrangement to Prevent Objectionable Current. The grounding of electrical systems, circuit conductors, surge arresters, and conductive non?current-carrying materials and equipment shall be installed and arranged in a manner that will prevent objectionable current over the grounding conductors or grounding paths.
(B) Alterations to Stop Objectionable Current. If the use of multiple grounding connections results in objectionable current, one or more of the following alterations shall be permitted to be made, provided that the requirements of 250.4(A)(5) or 250.4(B)(4) are met: "

One of the problems with this type of current flow is the high EMF developed, as the AC fields do not cancel as in a cable.

 

[don_resqcapt19]

Re: two grounds on one rod?

Roger,
I see a big difference between the bonding of two grounding systems and a parallel path for neutral current.
Don

 

[roger]

Re: two grounds on one rod?

Don, so do I, but if the "big brains" don't recognize it, (it can be and is the same thing in the right circumstance) where do they disclaim their reckless statements are wrong for young people to see and understand the diference?

I was fishing this time.

Roger

 

[karl riley]

Re: two grounds on one rod?

My take: there should be only one point where the GEC leaves to run to the electrode. If from both panel and meter then you have a senseless parallel path for neutral from the panel to the meter. If this path is very short it may be inconsequential (there's a word undefined by the NEC!) but why not do it the right way?

Karl(responding to Tom)

 

[dereckbc]

Re: two grounds on one rod?

inspector guy, is the neutral bonded to ground twice? If so you have a violation as stated above.

On the other hand, if the GEC to the meter box is bonded to the grounded conductor, and the panel box has an isolated neutral bus, with the second GEC connected to an EGC bus, then there is no code violation. There is no real benefit in doing this, but no harm done.

 

[pierre]

Re: two grounds on one rod?

Dereck
Draw a picture of your statement, then see if you will not have neutral current traveling on the GEC from the meter can to the panel.

Pierre

 

[dereckbc]

Re: two grounds on one rod?

Pierre, residential is not my area of expertise, commercial and industrial is. My point was if the neutral is only bonded once at the disconnect device, then you can add as many GEC's as you want downstream to the EGC circuits or buses. It is a common practice.

Maybee I missed something, but I was certainly not suggesting to bond the neutral twice as it would cause load current to flow in the EGC circuits.

THX

Dereck

 

[inspector_guy]

Re: two grounds on one rod?

Lots of information here. I have read all of this three times and am still trying to sort it all out. I will take some digital photos of the situation and pull the cover off of the panel too and take some pictures of that. The job was not permitted, and another job that the same fella did where he installed a 200 amp panel as an upgrade on a remodel job, he never ran an EGC from the panel at all. EGC is 'electrical grounding conductor', right? I will take the photos and post them with some infoprmation later this week.
Takk, Joe B.

 

[karl riley]

Re: two grounds on one rod?

EGC is equipment grounding conductor.
GEC is grounding electrode conductor.

Karl

 

[pierre]

Re: two grounds on one rod?

Dereck
My post was not meant to be malicious, I am sorry if you thought so. I was trying to point out what you said. Sometimes if one is to draw a picture of what they are thinking, it is easier to see.
I myself am going to purchase a drawing program and learn how to use it. There are some 'guys' who already do, and it is much easier to get a point across.
I happen to find your (as well as many other) posts very insightful and valuable.
Thanks

Pierre

 

[dereckbc]

Re: two grounds on one rod?

Piere, no offense was taken. Like I said residential is not my area. In residential I have seen at the meter where the GEC is brought in to the meter/disconnet, then a neutral and the two phases are ran to the main panel with no EGC. In the main panel,the grounded conductor bus bar is installed electricaly connected to the enclosure, then seperate EGC and neutral's are ran from there to individual branch circuits. If that is the setup, then I agree two GEC's are not compliant.

I may not understand what the poster was asking. But if the EGC originated at the disconnect, then you can add as many GEC downstream as you want to the EGC circuit, as long as it does not multi-ground the neutral..

THX

Dereck

 

[gwz2]

Re: two grounds on one rod?

I agree with Don and Karl about the parallel path of the neutral when a GEC originates in the meter enclosure and another GEC orginates in the Main Disconnect enclosure.

Problem is, as I see it, the Code permits this type of installation on Services.

That is the reason I had several proposals in a past Code-Cycle for "Single Point Grounding" of Services.

With metal water supplies through-out cities, the parallel path of the GEC(s) with the Grounded conductor (Neutral) can begin at the transformer pole (if the ground rod touches a metal water main) and be at every Service that the transformer serves.

That could be one service to many services, all with a GEC parallel to the Grounded Conductor back to the transformer.

I'm still for a 'single point ground' system, but do not know how it could ever be a reality when the NESC and the NEC would have to work together for EVERY service.

Glenn

[ August 18, 2003, 07:43 AM: Message edited by: gwz2 ]

 

[dereckbc]

Re: two grounds on one rod?

ED or somebody, can you draw a picture of the circuit the poster is describing. For the life of me I do not understand the parallel path here. Where is the EGC circuit originating?

 

[iwire]

Re: two grounds on one rod?

Dereck, The neutral is bonded to the enclosure at the meter and at the panel.

There is an grounding electrode conductor from the meter enclosure to the ground rod and an grounding electrode conductor from the panel to the ground rod.

Part of the neutral current will pass though one grounding electrode conductor through the ground rod and continue through the second grounding electrode conductor.

Another time this happens is if you have metal raceway between a meter socket and the service disconnect, part of the Neutral current will pass through the metal raceway.

I hope this helps, but one of Ed's drawings is always better.

Bob

[ August 18, 2003, 09:37 AM: Message edited by: iwire ]

 

[dereckbc]

Re: two grounds on one rod?

iwire, is that standard procedure for residential? If that is true then I agree the GEC to the panel needs to be removed.

 

[pierre]

Re: two grounds on one rod?

Dereck
The NEC requires the GEC connection to be accessible, and most Utility companies will not allow the connection in the meterpan. Therefore most times it is connected in the first point of disconnect of the premise wiring.The connection is permitted by code to be anywhere from the Service Point to the First Point of Disconnect (250.24(a)(1)). 250.24(a)(5) is where the requirement of not connecting after the service disconnecting means is found.
Does this help at all?

Pierre