# Multiple connections to one grounding rod



## jwjrw (Jan 14, 2010)

361biscuit said:


> Where can i find where it specifically talks about how many clamps or conducters i can attach to one ground rod?


 
I don't think there is a limit.


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## 361biscuit (Sep 11, 2010)

Is that referenced somewhere?


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## jwjrw (Jan 14, 2010)

361biscuit said:


> Is that referenced somewhere?


 
What is your situation? I usually have two on one rod and one on the other. I know of no section that say anything about how many. The code just tells you what is legal to use to make the connection.


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## 361biscuit (Sep 11, 2010)

I have several motors mounted on skids and would like to ground them together?


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## jwjrw (Jan 14, 2010)

361biscuit said:


> I have several motors mounted on skids and would like to ground them together?


 

A rod does not really "ground" a motor. Rods are more for lightning protection. I am not a big motor guy so I don't know if it's common to connect them to rods. Someone else will chime in I'm sure.

Do you mean "bond" them?


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## brian john (Mar 11, 2007)

Assuming these are connected to the electrical distribution system per the NEC they are grounded. Adding a rod will buy you nothing. 

Are these motor located outside?


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## BuzzKill (Oct 27, 2008)

jwjrw said:


> Do you mean "bond" them?


Guess he figures trying to tie them together, maybe?
Like Brian said, if they are wired correctly in the first place there is no need but if they are outside then they could use some lighting protection.


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## RIVETER (Sep 26, 2009)

If you drive a rod and connect it to the first motor you are actually grounding it. This purpose serves only for possible protection in the event of a lightning strike.If you tie the other motors via a conductor to the shells of them to the first, you are bonding them to the first and they are at ground potential. Sometimes it is confusing but it has nothing to do with the equipment grounding conductor even though it is at the same potential. The EGC is for the purpose of tripping the breaker if you have a hot to frame/shell/ground fault.


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## captkirk (Nov 21, 2007)

I almost never cut my ground wire to the rods. And you need one connector or acorn per wire...no doubling up


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## voltz (Jun 2, 2010)

BuzzKill said:


> Guess he figures trying to tie them together, maybe?
> Like Brian said, if they are wired correctly in the first place there is no need but if they are outside then they could use some lighting protection.


Are all parking lot lights required to have grounding rods? If so, could you quote code sec..


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## RIVETER (Sep 26, 2009)

voltz said:


> Are all parking lot lights required to have grounding rods? If so, could you quote code sec..


The ones we have do but I don't know if it is mandatory. However, it seems to me that if a rod is driven at each pole, a lightning event would have a preferred path to ground rather than send a high current into the building. Just my opinion. I know that some will say that the base and re-bar would be okay, and they would be correct.


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## brian john (Mar 11, 2007)

RIVETER said:


> The ones we have do but I don't know if it is mandatory. However, it seems to me that if a rod is driven at each pole, a lightning event would have a preferred path to ground rather than send a high current into the building. Just my opinion. I know that some will say that the base and re-bar would be okay, and they would be correct.


Time and a gain we are told Ufer grounds are best and testing bares this out. So you have a Ufer ground with the pole base right at every light but NOOOOOOOOOOOOOOO, when light poles are involved Ufers do not work?????????????????????????????


NEC does not mandate electrodes at each pole.


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## User14727 (Sep 2, 2010)

I'm probably wrong so someone rip my head off. But isn't the code worded so that a ground rod is only used to ground an electrical system(grounding elctrode)? 

250.30 (a) (3) Says on a single seperately derived system that a ground electrode can only be attached where the main bonding jumper is connected. So Im not sure but it seems that a ground rod tied to each pole would be the same as a ground electrode.

410.21 says that fixtures must be grounded by mean in 250.118 which just says conduits or wire to an EGC. An EGC must be connected via the main service to the electrode.

Just my thoughts, Seems like the question for me is, is a ground rod considered an electrode wherever it is put?


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## RIVETER (Sep 26, 2009)

brian john said:


> Time and a gain we are told Ufer grounds are best and testing bares this out. So you have a Ufer ground with the pole base right at every light but NOOOOOOOOOOOOOOO, when light poles are involved Ufers do not work?????????????????????????????
> 
> 
> NEC does not mandate electrodes at each pole.


The engineers who know more than we do,they think, are afraid to not take extra precautions.
The light pole, being bonded to the EGC gives an excellent path to ground via the EGC. I assume they know they have a UFER but just want some unnecessary redundancy.


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## brian john (Mar 11, 2007)

RIVETER said:


> The engineers who know more than we do,they think, are afraid to not take extra precautions.
> The light pole, being bonded to the EGC gives an excellent path to ground via the EGC. I assume they know they have a UFER but just want some unnecessary redundancy.


I seriously doubt it.


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## RIVETER (Sep 26, 2009)

brian john said:


> I seriously doubt it.


Which part do you doubt?


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## brian john (Mar 11, 2007)

RIVETER said:


> Which part do you doubt?


Engineers know or care they copy past specs and move on none the wiser.


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## brian john (Mar 11, 2007)

aguywithfeet said:


> I'm probably wrong so someone rip my head off. But isn't the code worded so that a ground rod is only used to ground an electrical system(grounding elctrode)?
> 
> 250.30 (a) (3) Says on a single seperately derived system that a ground electrode can only be attached where the main bonding jumper is connected. So Im not sure but it seems that a ground rod tied to each pole would be the same as a ground electrode.
> 
> ...


Depends on what you connect it to. driving an rod means nothing unless you connect it to something.

Ground rods are driven for lots of things, at generators, light poles, satellite dishes, telco systems, lightning protection systems.


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## RIVETER (Sep 26, 2009)

brian john said:


> Engineers know or care they copy past specs and move on none the wiser.


I can't dispute that; So what is your take on a ground rod at the pole?


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## brian john (Mar 11, 2007)

RIVETER said:


> I can't dispute that; So what is your take on a ground rod at the pole?


I cannot think of any cases I have seen or know of where they were a benefit, that does not mean anything in the whole scheme of things.

I make money off them, so hard to beat, recently had a job where we had to test every electrode at every pole 20 poles 60 test 4 days work, whats not to like?:whistling2:

Engineer just spending the federal Big "O" money.


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## RIVETER (Sep 26, 2009)

I see. Do you disagree with me about the effects of lightning,and about my belief that IF a ufer doesn't deplete a strike adequately, more current could go into a building and cause more problems?


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## brian john (Mar 11, 2007)

RIVETER said:


> I see. Do you disagree with me about the effects of lightning,and about my belief that IF a ufer doesn't deplete a strike adequately, more current could go into a building and cause more problems?


With lightning anything can and will happen, Did an investigation in Hanover PA where lightning hit a driven electrode, traveled on the copper into the building fried a IBM main frame. The electrode was driven as part of a VooDoo grounding IG system. The IBM was on a rubber pad with a PVC coupling installed in the feeder to isolate the main frame. lightning flashed across the coupling.

SO I have no idea if the electrodes help or not. BUT my guess is unnecessary.


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## RIVETER (Sep 26, 2009)

I believe that it is rare that anything can survive a direct lightning strike. It is probably a fact that most damage occurs due to a near strike. If the last gradient prior to entering the building is taken deeper, you would have, at least, another shot.


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## brian john (Mar 11, 2007)

RIVETER said:


> I believe that it is rare that anything can survive a direct lightning strike. It is probably a fact that most damage occurs due to a near strike. If the last gradient prior to entering the building is taken deeper, you would have, at least, another shot.



Actually many things survive lighting strikes it all depends on the magnitude and duration of the strike and what was hit.

But IMO if one rod helps lets drive two.


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## jwjrw (Jan 14, 2010)

brian john said:


> Actually many things survive lighting strikes it all depends on the magnitude and duration of the strike and what was hit.
> 
> But IMO if one rod helps lets drive two.


 
That explains why some people survive getting struck by lightning.


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## John Valdes (May 17, 2007)

BuzzKill said:


> Guess he figures trying to tie them together, maybe?
> Like Brian said, if they are wired correctly in the first place there is no need but if they are outside then they could use some lighting protection.


The lightning protection is provided by the EGC. No extra rod required. Of course we are assuming this is a compliant install?



RIVETER said:


> I can't dispute that; So what is your take on a ground rod at the pole?


My take is its a waste of time and money.


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## s.kelly (Mar 20, 2009)

John Valdes said:


> The lightning protection is provided by the EGC. No extra rod required. Of course we are assuming this is a compliant install?
> 
> 
> 
> My take is its a waste of time and money.


If so why is a lightning protection system have to have it's own ground rods?


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## RIVETER (Sep 26, 2009)

John Valdes said:


> The lightning protection is provided by the EGC. No extra rod required. Of course we are assuming this is a compliant install?
> 
> 
> > I don't believe that you should expect the EGC to be for lightning protection.


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## User14727 (Sep 2, 2010)

brian john said:


> Depends on what you connect it to. driving an rod means nothing unless you connect it to something.
> 
> Ground rods are driven for lots of things, at generators, light poles, satellite dishes, telco systems, lightning protection systems.


The one's you listed are all seperated systems though. In my experience we have never driven ground rods for anything electrical other than the electrode, besides at light poles which seems to always bring up this debate. I may be wrong.


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## brian john (Mar 11, 2007)

aguywithfeet said:


> The one's you listed are all seperated systems though. In my experience we have never driven ground rods for anything electrical other than the electrode, besides at light poles which seems to always bring up this debate. I may be wrong.


You are wrong. Electrodes are driven at generators, light poles, satellite dishes, telco systems, lightning protection systems for they same reason they are driven at light poles additional grounding STRICTLY with lighting in mind. 

I am not talking about code required grounding of a system conductor.


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## User14727 (Sep 2, 2010)

brian john said:


> You are wrong. Electrodes are driven at generators, light poles, satellite dishes, telco systems, lightning protection systems for they same reason they are driven at light poles additional grounding STRICTLY with lighting in mind.
> 
> I am not talking about code required grounding of a system conductor.


 I was trying to bring up a sidebar about this topic. Are ground rods even allowed according to code at light poles that are already grounded by the EGC? Wen are talking about tying(?) these rods to the EGC right?

Since you brought it up isn't the primary reason ground rods are driven at generators to create a low impedance path for the new service load side of the generator?


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## brian john (Mar 11, 2007)

aguywithfeet said:


> I was trying to bring up a sidebar about this topic. Are ground rods even allowed according to code at light poles that are already grounded by the EGC? Wen are talking about tying(?) these rods to the EGC right?


No different than the concrete base being a Ufer.



> Since you brought it up isn't the primary reason ground rods are driven at generators to create a low impedance path for the new service load side of the generator?


Depends on the ATS on a 3 phase 4 wire system with a 4 pole ATS, you need to ground XO at the generator or first disconnect. But with a 3 pole ATS the XO is grounded at the utility service and the electrodes are connected to the generator frame for lightning protection.

In either case they all should be connected together to form a single grounding electrode system.


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## Magnettica (Jan 23, 2007)

captkirk said:


> I almost never cut my ground wire to the rods. And you need one connector or acorn per wire...no doubling up


You're right 250.62(C)


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## Bob Badger (Apr 19, 2009)

aguywithfeet said:


> Are ground rods even allowed according to code at light poles that are already grounded by the EGC? Wen are talking about tying(?) these rods to the EGC right?


The NEC allows adding as many electrodes as you would like connected to the EGC.



> *250.54 Auxiliary Grounding Electrodes.* One or more
> grounding electrodes shall be permitted to be connected to
> the equipment grounding conductors specified in 250.118
> and shall not be required to comply with the electrode
> ...


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## User14727 (Sep 2, 2010)

The ufer is tied into the electrode directly though. It becomes a part of the system electrode. To me it seems like the ground rods at light poles are creating a secondary path for a ground fault. If for some crazy reason you lost your ground at the service the fault could potentially flow through the EGC to these rods correct? Would this not be a parallel ground path? Isn't that against code?

I am not trying to argue, i am trying to understand. THis is the best way for me.


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## User14727 (Sep 2, 2010)

Bob Badger said:


> The NEC allows adding as many electrodes as you would like connected to the EGC.


Well there ya go. Thank you, didn't see that.


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## Bob Badger (Apr 19, 2009)

aguywithfeet said:


> Well there ya go. Thank you, didn't see that.


Up until the 2008 NEC that section was called supplementary electrodes.

One of the members here and someone I consider a friend put in a proposal to have it changed.

You have to love George's style. :thumbsup:




> 5-170 Log #1398 NEC-P05 Final Action: Accept in Principle
> (250.54)
> ____________________________________________________________
> *Submitter:* George Stolz, II, Pierce, CO
> ...


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## brian john (Mar 11, 2007)

aguywithfeet said:


> The ufer is tied into the electrode directly though. It becomes a part of the system electrode. To me it seems like the ground rods at light poles are creating a secondary path for a ground fault. If for some crazy reason you lost your ground at the service the fault could potentially flow through the EGC to these rods correct? Would this not be a parallel ground path? Isn't that against code?
> 
> I am not trying to argue, i am trying to understand. This is the best way for me.



Assuming a ground fault.

The driven electrode is no different that the concrete base. If the soil has low enough resistance to pass current in a fault, the base would be exactly the same as the driven electrode. BUT the copper EGC should have a lower resistance and the fault would return to the service transformer through the EGC. Assume you lost the main bonding jumper at the service then the light poles would do nothing, you'd have an ungrounded service and would not have a ground fault, you'd have a grounded system through the phase that shorted to ground.

Now if you lost the EGC at the pole and the EARTH had a low enough resistance then an driven electrode would only lower the resistance improving the fault path. BUT the earth seldom has a low enough resistance to operate a OCP at 120-480 VAC.


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