# Ground Rod or Not?



## Lenny (Nov 19, 2009)

We are installing new electric service in a campground. Each site has a 50/30/20 amp metered pedistal, fed on 5 site loop with sweetbriar {4/0-4/0-2/0 alum} from a 200 amp disconnect. A seperate #2 alum bond is also run. Some professionals say a ground-rod is required for each pedistal, others say that would be unessary, even others say it would pose a safty hazzard.

What does the forum think?

*The 20 amp receptical is a GFCI, there are 4 disconnects per transformer, there are 2 ground rods at the disconnects bonded to the neutral

Thanks

Lenny


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## RIVETER (Sep 26, 2009)

*Camp Ground*

You said that you are running a # 2 bond...I assume that you mean a #2 GEC. Is that correct?


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## sparks134 (Jan 30, 2009)

I believe you still needa ground rod!


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## RIVETER (Sep 26, 2009)

*kCamp Ground*



sparks134 said:


> I believe you still needa ground rod!


I agree with you. The NEC is just the BARE minimum that you must do...Other efforts are even better.


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## user5941 (Mar 16, 2009)

If you are running an EGC to each pedestal and bonding all the pedestals then a ground rod at each pad is not needed or required.


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## RIVETER (Sep 26, 2009)

*Camp Ground*



rewire said:


> If you are running an EGC to each pedestal and bonding all the pedestals then a ground rod at each pad is not needed or required.


I won't disagree with you on this. But remember, the NEC is the MINIMUM that you have to do.


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## user5941 (Mar 16, 2009)

RIVETER said:


> I won't disagree with you on this. But remember, the NEC is the MINIMUM that you have to do.


 what function would a ground rod at each pedestal preform?


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## Lenny (Nov 19, 2009)

In florida a single ground rod usually doesnt make a low ohm connection. The one argument was that they all would work together. As far as saftey, I feel the bond is most important. My opinion is not to use ground rods. 
The argument against them is a far fetched sernario described below:

Site A has a fault in unit & ground-rod is inoperable & bond to site B is broken. Site B has proper ground-rod. It is possible to touch RV's at same time, causing shock.

Again, a far fetched senario in my opinion.



Riveter, what is a GEC? if its the grounded conductor, no we are using a 2/0.
The #2 is the bonded ground

thanks

lenny


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## user5941 (Mar 16, 2009)

the code says you need a minimum of 25 ohm ground rod , you drive a rod at the pedestal and it is at 25 ohms now lets do some math 120 volts divided by 25 ohms gives you 4.8 amps so you have 4.8 amps on your ground rod tell me how this is going to clear a 20 amp breaker.


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## RIVETER (Sep 26, 2009)

*Ground Rod*



Lenny said:


> In florida a single ground rod usually doesnt make a low ohm connection. The one argument was that they all would work together. As far as saftey, I feel the bond is most important. My opinion is not to use ground rods.
> The argument against them is a far fetched sernario described below:
> 
> Site A has a fault in unit & ground-rod is inoperable & bond to site B is broken. Site B has proper ground-rod. It is possible to touch RV's at same time, causing shock.
> ...


I will be honest with you. I did not read your whole post. I DO know that the Florida area does not have the best DIRT to find a consistant LOW ohmage to ground. I will say that the purpose of, and the ONLY, purpose of the GEC (Grounding Electrode Conductor), is for lightning strikes, or possible abberant voltages such as a higher voltage line falling on a lower voltage line. Or, it could be a primary to secondary short circuit on the service transformer.


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## Lenny (Nov 19, 2009)

the 25 ohm requirement makes sense to me, it makes sure the gec is actually grounded. The electrician who wants rods only cares about one per site citing that they will all work togather. My thoughts are that if you dont get down to a 25 ohm resistance you have wasted your time with the rods. The NEC says that the earth shall not be considered the bonded ground, which tells me to leave the rods out. 
I own the campground, but we have a licensed electrician on staff, so we do our own work under my guidence. He sites many things as being REQURIED BY LAW, but I am unable to find them in nec.

Also, wouldn't you consider the NEC to be quite better than the bare minimum?

thanks

lenny


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## RIVETER (Sep 26, 2009)

*Camp Ground*



Lenny said:


> the 25 ohm requirement makes sense to me, it makes sure the gec is actually grounded. The electrician who wants rods only cares about one per site citing that they will all work togather. My thoughts are that if you dont get down to a 25 ohm resistance you have wasted your time with the rods. The NEC says that the earth shall not be considered the bonded ground, which tells me to leave the rods out.
> I own the campground, but we have a licensed electrician on staff, so we do our own work under my guidence. He sites many things as being REQURIED BY LAW, but I am unable to find them in nec.
> 
> Also, wouldn't you consider the NEC to be quite better than the bare minimum?
> ...


No , I would not...The NEC is the BARE minimum. AND...There is a vast difference between GROUNDING and BONDING>


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## user5941 (Mar 16, 2009)

Lenny said:


> the 25 ohm requirement makes sense to me, it makes sure the gec is actually grounded. The electrician who wants rods only cares about one per site citing that they will all work togather. My thoughts are that if you dont get down to a 25 ohm resistance you have wasted your time with the rods. The NEC says that the earth shall not be considered the bonded ground, which tells me to leave the rods out.
> I own the campground, but we have a licensed electrician on staff, so we do our own work under my guidence. He sites many things as being REQURIED BY LAW, but I am unable to find them in nec.
> 
> Also, wouldn't you consider the NEC to be quite better than the bare minimum?
> ...


 If you were being graded and all you did was just to code you would get a D


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## Lenny (Nov 19, 2009)

I think I am correct in that a bond is simply an electrically conductive connection, while a ground is a connection to earth. 

So, it is common to bond the ungrounded conductors, as in my loop feed. Saying that your bonding hot legs gets a lot of funny looks around here.

thanks

Lenny


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## william1978 (Sep 21, 2008)

........................


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## RIVETER (Sep 26, 2009)

*Ground Rod...or not*



Lenny said:


> I think I am correct in that a bond is simply an electrically conductive connection, while a ground is a connection to earth.
> 
> So, it is common to bond the ungrounded conductors, as in my loop feed. Saying that your bonding hot legs gets a lot of funny looks around here.
> 
> ...


In your first paragraph, you are correct. In the second paragraph, I am not sure what you are saying.


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## wareagle (Jan 10, 2009)

rewire said:


> the code says you need a minimum of 25 ohm ground rod , you drive a rod at the pedestal and it is at 25 ohms now lets do some math 120 volts divided by 25 ohms gives you 4.8 amps so you have 4.8 amps on your ground rod tell me how this is going to clear a 20 amp breaker.


 *No where in the NEC does it say you need a minimum 25 ohm ground rod. I do agree with you math. Thats why you install an EGC.*


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## Lenny (Nov 19, 2009)

As soon as you say bond, everyone {at least around here} assumes ground. But Bond, Bonded or Bonding simply means "connected". Reading through the NEC thinking bond=ground horribly screws up interpritations.


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## amptech (Sep 21, 2007)

rewire said:


> the code says you need a minimum of 25 ohm ground rod , you drive a rod at the pedestal and it is at 25 ohms now lets do some math 120 volts divided by 25 ohms gives you 4.8 amps so you have 4.8 amps on your ground rod tell me how this is going to clear a 20 amp breaker.


Clearing a 20A breaker is not what a grounding electrode is for. Do you understand the purpose of installing a grounding electrode at each structure served?


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## amptech (Sep 21, 2007)

rewire said:


> what function would a ground rod at each pedestal preform?


Maintain potential.


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## Lenny (Nov 19, 2009)

Two things,

I dont really know the purpose of a ground rod at every site, what is it?

Does everyone feel that the NEC is a bare minimum, a grade of a D?

Thanks

Lenny


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## RIVETER (Sep 26, 2009)

*Grounding or Not*



Lenny said:


> As soon as you say bond, everyone {at least around here} assumes ground. But Bond, Bonded or Bonding simply means "connected". Reading through the NEC thinking bond=ground horribly screws up interpritations.


Bonding means BEING AS ONE. As far as electrical considerations, it means that if you have a grounded system...GROUND ROD... you have connected a circuit conductor to ground potential. You are limiting that voltage to GROUND. It has very little to do with BONDING.


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## sparks134 (Jan 30, 2009)

A ground rod is good for one thing, lighting protection!!!


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## user5941 (Mar 16, 2009)

wareagle said:


> *no where in the nec does it say you need a minimum 25 ohm ground rod. I do agree with you math. Thats why you install an egc.*


 250.56


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## user5941 (Mar 16, 2009)

Lenny said:


> Two things,
> 
> I dont really know the purpose of a ground rod at every site, what is it?
> 
> ...


 the purpose of bonding and grounding is to create a low impedance path back to the source to clear the fault.


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## Lenny (Nov 19, 2009)

Riviter,

So, you agree that bonding refers to electrically connecting something, not tying it to ground, right?

In my case, we have bonded all the pedistals with a #2 alum. conductor and connected that to the ground-rods at the disconnects, which are also tied to the neutral. All disconnects are bonded also.

I value your opinion, I don't want to come off as a smartass. I get a lot of bad advice from local electricans. I do have, and can read and follow a copy of the latest NEC

thanks

Lenny


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## sparks134 (Jan 30, 2009)

The main service disconnect is the only place that needs to be bonded


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## sparks134 (Jan 30, 2009)

your ground and neutral should not be bonded at the subpanel!!!


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## Lenny (Nov 19, 2009)

Rewire,

I think I understand "the purpose of bonding and grounding is to create a low impedance path back to the source to clear the fault." But how would a ground-rod at every pedistal add protection, especially if they don't get down to 25 ohms?

When you say "clear the fault" is that tripping a breaker or GFCI?

Also, as I understand no connection can be made between the un-grounded conducter and the bonding conducter on the load side of the disconnects. Do you agree?

Thanks

Lenny


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## Lenny (Nov 19, 2009)

Sparks134,

I understand that the ground and the neutral cannot be connected in the sub-panel. I dont have a clear understanding why? Older wiring used to allow that correct? Why the change?

thanks

Lenny


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## Benaround (May 5, 2009)

sparks134 said:


> your ground and neutral should not be bonded at the subpanel!!!


 These are not sub-panels, the OP stated 'metered pedistals' as new services.


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## sparks134 (Jan 30, 2009)

Well they still need a ground rod!!!


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## Lenny (Nov 19, 2009)

Benaround,

I should clear that meter thing up. The meters are owned by the campground, to charge for monthly electric usage. There is one CT meter per transformer, one transformer feeds 4 disconnects, one disconnect feeds 5 pedistals. As far as the utility company is concerend there is 1 service.

thanks

lenny


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## sparks134 (Jan 30, 2009)

Then I was right, no bonding and a ground rod!!!


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## wareagle (Jan 10, 2009)

rewire said:


> 250.56


Suggest you read that again. It does not say you need a 25 ohm ground rod. It says that if the resistance of the ground rod is more that 25 ohms you need to install another rod and bond the two rods together. The resultant rod resistance is not mentioned or required. If the rod measures 1000 ohms you install another rod and walk away. Please read 250.56 again so you understand the requirement.


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## sparks134 (Jan 30, 2009)

Lenny said:


> Benaround,
> 
> I should clear that meter thing up. The meters are owned by the campground, to charge for monthly electric usage. There is one CT meter per transformer, one transformer feeds 4 disconnects, one disconnect feeds 5 pedistals. As far as the utility company is concerend there is 1 service.
> 
> ...


Where do you buy meters from to charge custumers? I never heard of that, just wondering!!


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## RIVETER (Sep 26, 2009)

*Grounding etc.*



rewire said:


> the purpose of bonding and grounding is to create a low impedance path back to the source to clear the fault.


Can you tell me why everyone is concerned about IMPEDENCE...Rather than RESISTANCE?


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## Lenny (Nov 19, 2009)

I belive Wareagle is correct on the ground rod requirement, i've read it several times- but a rod with a 1000 ohms isn't doing much is it? Another reason I dont like the idea of ground rodding every pedistal.

Sparks,

Meters are avaliable from many companys. Midwest Supply, Utility Supply Group and Travellers are some suppliers in this industry. It is common for a Campground or RV park to charge monthly customers for electric. Some parks also charge more for 50 amp service.


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## Lenny (Nov 19, 2009)

Riviter,

I asked that also, got a lot of shady answers. I think the real answer is that a "Megger" is needed to test the effectivness of a ground rod, and no one has them so they use the ohm meter.


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## amptech (Sep 21, 2007)

rewire said:


> the purpose of bonding and grounding is to create a low impedance path back to the source to clear the fault.


That is a mostly true statement but incomplete. The purpose of a grounding electrode is to maintain earth potential(zero) at electrical equipment. Does each pedestal require a grounding electrode? I suggest you read 250.50 carefully then also read 551.74. If you have not read Soares Book on Grounding, I would highly recommend it. Soares explains grounding and bonding very well and clears up a lot of misconceptions and misinformation about grounding and bonding.


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## amptech (Sep 21, 2007)

I should clarify my previous posts. I was referencing the 2008 NEC articles 250 and 551. 551.75 references RV park site electrical equipment grounding which refers you back to the requirements of article250. Article 250.50 requires a grounding electrode at "each building or structure served". An electrical pedestal, by most definitions, is a structure. And yes, you would want the electrode installed and bonded to all metal parts of the pedestal enclosure to maintain zero potential between the metallic parts and the earth.


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## sparks134 (Jan 30, 2009)

not bonded!


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## amptech (Sep 21, 2007)

If you are talking about the neutral or grounded conductor, then you are correct. The electrode should not be bonded to the neutral or grounded conductor, only the metallic parts of the enclosure and the EGC lug/bar. The neutral or grounded conductor should only be grounded at the 1st point of over-current protection(service disconnect point).


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## Lenny (Nov 19, 2009)

Amptec,

I know the code says you cannot bond the ungrounded conductor {neutral} to the grounded bond {ground} after the disconnect. Why? Was this always the case?

thanks

Lenny


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## cdnelectrician (Mar 14, 2008)

RIVETER said:


> Can you tell me why everyone is concerned about IMPEDENCE...Rather than RESISTANCE?


Resistance is the opposition of current flow, Impedance is the oppostion of current flow at a given frequency (lightning for example)


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## user5941 (Mar 16, 2009)

wareagle said:


> Suggest you read that again. It does not say you need a 25 ohm ground rod. It says that if the resistance of the ground rod is more that 25 ohms you need to install another rod and bond the two rods together. The resultant rod resistance is not mentioned or required. If the rod measures 1000 ohms you install another rod and walk away. Please read 250.56 again so you understand the requirement.


 I was just making an example I was not trying to establish a code reference if you will go back and read I did not say "SHALL" have.I was just using the reference to 25 ohms givin in the code I realize that you are not required to have a resistance of 25 ohms and that two ground rods are all you need to drive no matter what the ohm measurement.I will attempt to reword any future examples so that it will not add confusion I should have worded it to say the code says you need 25 ohms on a ground rod or you need to drive one additional rod and then gone into the math problem.I am sorry this confused you and I wil;l endevor to clarify my future references so that you will understand them better :thumbsup:


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## user5941 (Mar 16, 2009)

amptech said:


> I should clarify my previous posts. I was referencing the 2008 NEC articles 250 and 551. 551.75 references RV park site electrical equipment grounding which refers you back to the requirements of article250. Article 250.50 requires a grounding electrode at "each building or structure served". An electrical pedestal, by most definitions, is a structure. And yes, you would want the electrode installed and bonded to all metal parts of the pedestal enclosure to maintain zero potential between the metallic parts and the earth.


 structure - that which is built or constructed
We need a few inspectors to weigh in. Is a cabinet a structure ?


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## amptech (Sep 21, 2007)

rewire said:


> If you are running an EGC to each pedestal and bonding all the pedestals then a ground rod at each pad is not needed or required.


I believe this statement is incorrect per the NEC articles I have posted.


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## amptech (Sep 21, 2007)

rewire said:


> structure - that which is built or constructed
> We need a few inspectors to weigh in. Is a cabinet a structure ?


Don't you install an electrode at a temporary power pole?


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## amptech (Sep 21, 2007)

2008 NEC Article 250.32" Buildings or Structures Supplied by a Feeder(s) or Branch Circuit(s).(A) Grounding Electrode. Building(s) or structure(s) supplied by feeder(s) or branch circuit(s) shall have a grounding electrode or grounding electrode system installed in accordance with Part III of Article 250." 
If it has feeders or branch circuits ran to it then it must be a structure, right? You couldn't run them to a non-structure, could you? Someone had to build the pedestal that was installed.
I have designed/installed the distribution systems for several mobile home parks and campgrounds, some of them state park RV park/campgrounds. Grounding electrodes at pedestals are required and necessary to maintain potential at campsites. If you understand the purpose and function of the grounding electrode system you understand why they are especially important in this type of situation.


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## user5941 (Mar 16, 2009)

amptech said:


> 2008 NEC Article 250.32" Buildings or Structures Supplied by a Feeder(s) or Branch Circuit(s).(A) Grounding Electrode. Building(s) or structure(s) supplied by feeder(s) or branch circuit(s) shall have a grounding electrode or grounding electrode system installed in accordance with Part III of Article 250."
> If it has feeders or branch circuits ran to it then it must be a structure, right? You couldn't run them to a non-structure, could you? Someone had to build the pedestal that was installed.
> I have designed/installed the distribution systems for several mobile home parks and campgrounds, some of them state park RV park/campgrounds. Grounding electrodes at pedestals are required and necessary to maintain potential at campsites. If you understand the purpose and function of the grounding electrode system you understand why they are especially important in this type of situation.


 We installed light poles that the drawings did not call for a ground rod nor did the inspector require it.He said a light pole was not a building or structure so I think the AHJ should be talked to.


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## user5941 (Mar 16, 2009)

I am taking a CEU class on mondays and I think I just found my question to ask the instructor.


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## amptech (Sep 21, 2007)

rewire said:


> We installed light poles that the drawings did not call for a ground rod nor did the inspector require it.He said a light pole was not a building or structure so I think the AHJ should be talked to.


Were your light poles fed by a feeder or more than one branch circuit? A light pole is indeed a structure, it just doesn't meet the above mentioned criteria to require a grounding electrode.


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## amptech (Sep 21, 2007)

I have installed parking lot light poles that did require a grounding electrode. They had disconnects mounted on them and receptacles. They were fed by a feeder or more than one branch circuit thus requiring the electrode.


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## amptech (Sep 21, 2007)

A yard shed with one 120V branch circuit or one MWBC serving it does not require a grounding electrode system. The same shed served by a feeder or more than one branch circuit requires a grounding electrode system.


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## sparks134 (Jan 30, 2009)

amptech said:


> A yard shed with one 120V branch circuit or one MWBC serving it does not require a grounding electrode system. The same shed served by a feeder or more than one branch circuit requires a grounding electrode system.


 YES! This is correct, so a subpanel would be ok, taking in consideration the 6 hand rule and ground rod(s) need to be put in place.


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## sparks134 (Jan 30, 2009)

amptech said:


> Were your light poles fed by a feeder or more than one branch circuit? A light pole is indeed a structure, it just doesn't meet the above mentioned criteria to require a grounding electrode.


 This is also correct! Good statment.


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## raider1 (Jan 22, 2007)

rewire said:


> We installed light poles that the drawings did not call for a ground rod nor did the inspector require it.He said a light pole was not a building or structure so I think the AHJ should be talked to.


A light pole is a structure but the exception to 250.32(A) permits us to not install a grounding electrode if the structure is fed by a single branch circuit (For the purpose of the exception a multiwire branch circuit is considered a single circuit).

Chris


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## sparks134 (Jan 30, 2009)

raider1 said:


> A light pole is a structure but the exception to 250.32(A) permits us to not install a grounding electrode if the structure is fed by a single branch circuit (For the purpose of the exception a multiwire branch circuit is considered a single circuit).
> 
> Chris


 Yes, you are correct!!


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## user5941 (Mar 16, 2009)

amptech said:


> Don't you install an electrode at a temporary power pole?


 your dealing with a service now


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## amptech (Sep 21, 2007)

Bump

Where did everyone go? I am interested in rewire's rationale for not installing a grounding electrode at a RV campsite pedestal.


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## user5941 (Mar 16, 2009)

amptech said:


> Bump
> 
> Where did everyone go? I am interested in rewire's rationale for not installing a grounding electrode at a RV campsite pedestal.


 I'm going to get a ruling on this monday , I may have to change my thinking and I may not. currently I do not view a pedestral as a structure as defined in art 100 I think a grounding conductor and bonding would be all that is required I will note I have never done a metered campround but have connected power outlets to sites. I am basing this on the definition as I see it but I am not an AHJ so I am going to talk to one from Saint Louis City .I am not saying i can't be wrong on this.


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## amptech (Sep 21, 2007)

Rewire,
I am curious to know if you have read Soares Book on Grounding that I mentioned in earlier posts. If not, you should check it out. I think you would find it interesting.


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## user5941 (Mar 16, 2009)

amptech said:


> Rewire,
> I am curious to know if you have read Soares Book on Grounding that I mentioned in earlier posts. If not, you should check it out. I think you would find it interesting.


 no I haven't still reading MH book


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## Benaround (May 5, 2009)

Lenny said:


> In my case, we have bonded all the pedistals with a #2 alum. conductor and connected that to the ground-rods at the disconnects, which are also tied to the neutral. All disconnects are bonded also.


Lenny,

That would amount to an EGC connecting to a ground rod, the EGC

terminates on or after the N/Grd connection.


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## JohnJ0906 (Jan 22, 2007)

amptech said:


> That is a mostly true statement but incomplete. The purpose of a grounding electrode is to maintain earth potential(zero) at electrical equipment. Does each pedestal require a grounding electrode? I suggest you read 250.50 carefully then also read 551.74. If you have not read Soares Book on Grounding, I would highly recommend it. Soares explains grounding and bonding very well and clears up a lot of misconceptions and misinformation about grounding and bonding.


Also, I think a good look at 250.4(A)(1 through 5) is in order as well.

"The following general requirements identify what grounding and bonding of electrical systems are required to accomplish......."


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## AllStar (Nov 19, 2009)

amptech said:


> Maintain potential.


 A ground rod is not to maintain potential, but solely to give lightning a direct path to earth. When you say equal potential, it usually refers to the bonding ring around swimming pools, which gives you the equi potential to all metal parts surounding the pool. ie.. pool light, ladder, dive platform.


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## JayH (Nov 13, 2009)

AllStar said:


> A ground rod is not to maintain potential, but solely to give lightning a direct path to earth.


 
Are you serious? :001_huh:


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## brian john (Mar 11, 2007)

JayH said:


> Are you serious? :001_huh:


 
He is.

What do you think the purpose of an electrode is?


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## NolaTigaBait (Oct 19, 2008)

JayH said:


> Are you serious? :001_huh:


are you?


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## JayH (Nov 13, 2009)

brian john said:


> He is.
> 
> What do you think the purpose of an electrode is?


 
A grounding electrode is not *solely *for lightning protection.

Rather than spend my time typing out all of the needs for ground I have copied and pasted for you:

The purpose of grounding is three-fold. First, grounding provides a low-impedance path for fault current to flow back to the source. In accordance with Ohm’s Law (V = I x R), a low-impedance path for fault current results in high levels of current to flow for a given voltage. For inverse-time overcurrent protective devices, such as circuit breakers and fuses, higher levels of fault current cause faster device operation to clear the fault. Grounding provides a low-impedance path for fault current to ensure that circuit breakers and fuses operated quickly to clear ground-faults from the system.


Second, the low-impedance path for fault current provided by grounding ensures that voltage drop is limited from the point of the ground-fault back to the source. Ground-fault current is safely shunted to ground through a low-impedance path to ground before voltage can rise to lethal levels on any electrical component, protecting personnel from shock hazards during ground-fault conditions.


Third, grounding provides an electrical reference to stabilize the voltage to earth on conductors and equipment to the system phase-to-ground voltage during normal operation. An ungrounded system permits the voltage to earth on conductors and equipment to rise to levels as high as the phase-to-phase voltage during ground-fault conditions. Grounding provides an electrical reference for equipment operation that limits the voltage stress on conductor and equipment insulation throughout the system, and also limits the voltage imposed by lightning, switching surges, or unintentional contact with higher-voltage lines.


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## sparks134 (Jan 30, 2009)

yes, for lightning!!!:thumbsup:


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## bthesparky (Jan 23, 2009)

Ok heres the situation, did a 200 amp resy service today drove my 8ft. ground rod 3ft. off the foundation and at a more then adequate depth. The inspector comes out, looks everything over likes the work and is very happy and then proceeds to ask me where my second ground rod is. The utility company's service guidelines show nothing about having to have the second rod and he's trying to tell me that a second rod is a code requirement. I dont claim to be the sharpest guy but i do know how to read a code book and i see nothing about this second ground rod. I did find out by talking to the utility guy that they are now requiring it which is fine but i would like to know if its a code requirement that im missing. Thanks for any answers you guys can offer.


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## JayH (Nov 13, 2009)

There is not a NEC code requirement as long as you have not exceeded 25 ohms resistance and you have driven an 8' rod.

If there is a local code then you need to tell the inspector "show it to me."


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## wareagle (Jan 10, 2009)

Unless you can show that the ground rod resistance is 25 ohms or lower you have to drive a second rod. Most electricians do not bother to test the resistance. They just drive the second rod.


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## JohnJ0906 (Jan 22, 2007)

JayH said:


> A grounding electrode is not *solely *for lightning protection.
> 
> Rather than spend my time typing out all of the needs for ground I have copied and pasted for you:
> 
> ...


The grounding electrode, and the planet earth has nothing to do with what I highlighted in red.

Take a look at 250.4(A)(1 through 5) - especially (5)


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## surfbh (Jun 1, 2008)

cdnelectrician said:


> Resistance is the opposition of current flow, Impedance is the oppostion of current flow at a given frequency (lightning for example)


Lots of bad info in this post, but this definition of impedance is totally wrong! Impedance is the total opposition to current flow. It is the algebraic sum of resistance, capacitive reactance and inductive reactance.


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## brian john (Mar 11, 2007)

> The purpose of grounding is three-fold. First, grounding provides a low-impedance path for fault current to flow back to the source. In accordance with Ohm’s Law (V = I x R), a low-impedance path for fault current results in high levels of current to flow for a given voltage. For inverse-time overcurrent protective devices, such as circuit breakers and fuses, higher levels of fault current cause faster device operation to clear the fault. Grounding provides a low-impedance path for fault current to ensure that circuit breakers and fuses operated quickly to clear ground-faults from the system.


NOT THE PURPOSE OF A GROUND ELECTRODE Grounding/bonding yes Ground Electrode NO, NO, NO.




> Second, the low-impedance path for fault current provided by grounding ensures that voltage drop is limited from the point of the ground-fault back to the source. Ground-fault current is safely shunted to ground through a low-impedance path to ground before voltage can rise to lethal levels on any electrical component, protecting personnel from shock hazards during ground-fault conditions.


NOT THE PURPOSE OF A GROUND ELECTRODE Grounding/bonding yes; Ground Electrode NO, NO, NO.





> Third, grounding provides an electrical reference to stabilize the voltage to earth on conductors and equipment to the system phase-to-ground voltage during normal operation. An ungrounded system permits the voltage to earth on conductors and equipment to rise to levels as high as the phase-to-phase voltage during ground-fault conditions. Grounding provides an electrical reference for equipment operation that limits the voltage stress on conductor and equipment insulation throughout the system,


NOT THE PURPOSE OF A GROUND ELECTRODE Grounding/bonding yes Ground Electrode; NO, NO, NO.





> and also limits the voltage imposed by lightning, switching surges, or unintentional contact with higher-voltage lines.


You finally hit on something.


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## amptech (Sep 21, 2007)

Brian,
I guess someone should have corrected Soares before they started publishing and distributing his book. 
In the situation described in the original post there is a good possibility of a difference in potential between the metallic enclosure of the pedestal and the surrounding earth if no electrode is present. Lightning protection is a big part of the reasoning for grounding electrodes but touch potential is as well. Touch potential can be deadly in a situation as described in the OP. Wet ground, bare feet and a lot of physical contact likely with the pedestal. A human body touching the enclosure will be a shorter path than the lengthy #2 AL EGC and will likely conduct a good portion of stray current.
If you would indulge me, I'd like to hear your reasoning for disagreement with Soares on this point. Maybe I need to be corrected in my understanding.


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## JayH (Nov 13, 2009)

brian john said:


> NOT THE PURPOSE OF A GROUND ELECTRODE Grounding/bonding yes Ground Electrode NO, NO, NO.
> 
> 
> 
> ...


Can you have grounding without a grounding electrode?


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## brian john (Mar 11, 2007)

JayH said:


> Can you have grounding without a grounding electrode?


 
Bonding/grounding of an electrical distribution system is completed everyday, whether the ground electrode is worth a damn is seldom to never determined. Do you test your eelectrodes.

Do you think a 25 ohm electrode is going to do anything in the cases you sited?


Do not skirt the issue with paste of someone eles post or something you copied from a book.

TELL ME HOW??????????????


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## brian john (Mar 11, 2007)

amptech said:


> Brian,
> I guess someone should have corrected Soares before they started publishing and distributing his book.
> In the situation described in the original post there is a good possibility of a difference in potential between the metallic enclosure of the pedestal and the surrounding earth if no electrode is present. Lightning protection is a big part of the reasoning for grounding electrodes but touch potential is as well. Touch potential can be deadly in a situation as described in the OP. Wet ground, bare feet and a lot of physical contact likely with the pedestal. A human body touching the enclosure will be a shorter path than the lengthy #2 AL EGC and will likely conduct a good portion of stray current.
> If you would indulge me, I'd like to hear your reasoning for disagreement with Soares on this point. Maybe I need to be corrected in my understanding.


Touch potential at 120 VAC, at what resistance to ground DO YOU KNOW, DO YOU CARE. I assume you test every electrode you install to get it what; below 25 ohms, 5 ohms, 1 ohms. 

Tell me please?


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## NolaTigaBait (Oct 19, 2008)

I think you scared him away:laughing:.


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## AllStar (Nov 19, 2009)

brian john said:


> not the purpose of a ground electrode grounding/bonding yes ground electrode no, no, no.
> 
> 
> 
> ...


 thank you!!!


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## wareagle (Jan 10, 2009)

JayH said:


> Can you have grounding without a grounding electrode?


You can have an electrical system that works with out a grounding electrode. Some time we used the word grounding when we should be saying bonding. Most of what you said in your other post refers to bonding. You last statement *"and also limits the voltage imposed by lightning, switching surges, or unintentional contact with higher-voltage lines "*, applies to the grounding electrode.


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## brian john (Mar 11, 2007)

wareagle said:


> You can have an electrical system that works with out a grounding electrode. Some time we used the word grounding when we should be saying bonding. Most of what you said in your other post refers to bonding. You last statement *"and also limits the voltage imposed by lightning, switching surges, or unintentional contact with higher-voltage lines "*, applies to the grounding electrode.


And there in lies the confusion.


I've always wanted to know, how is a tiger a wareagle? GO AUBURN!


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## wareagle (Jan 10, 2009)

brian john said:


> And there in lies the confusion.
> I've always wanted to know, how is a tiger a wareagle? GO AUBURN!


Thanks for asking. This site explains it better than I can.

http://en.wikipedia.org/wiki/War_Eagle


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## JayH (Nov 13, 2009)

NolaTigaBait said:


> I think you scared him away:laughing:.


Nah, not scared away, just had to get some rest.

And I'm not afraid to be proven wrong.

But 250.4(A)(1):

Electrical Grounding System. Electrical systems that are grounded shall be connected to earth in a manner that will limit the voltage imposed by lightning, line surges, or unintentional contact with higher-voltage lines _and that will stabilize the voltage to earth during normal operation._

Here in California we do not consider lightning strikes to be normal operation.


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## JayH (Nov 13, 2009)

brian john said:


> Touch potential at 120 VAC, at what resistance to ground DO YOU KNOW, DO YOU CARE. I assume you test every electrode you install to get it what; below 25 ohms, 5 ohms, 1 ohms.
> 
> Tell me please?


On the majority of projects I am involved we are required to test and document all grounding electrodes. We are typically required to meet the NEC standard of 25 ohms.

I worked on one facility that required much lower resistance, but I cannot remember exactly how low. It was a military testing facility where all conduit was required to be aluminum rigid.


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## amptech (Sep 21, 2007)

brian john said:


> Touch potential at 120 VAC, at what resistance to ground DO YOU KNOW, DO YOU CARE. I assume you test every electrode you install to get it what; below 25 ohms, 5 ohms, 1 ohms.
> 
> Tell me please?


Brian,
I am not referring to the electrical system's main grounding electrode or the 25 ohm reference point mentioned in the NEC. I am aware that as you move in any direction from a driven rod electrode or any other made electrode you have a dissipating effect due to the shell effect, but in the immediate area where an electrode is installed and connected to metallic enclosures of electrical equipment this should achieve zero or very near zero potential between the earth surrounding the electrode and the metallic parts it is bonded to. It is in turn connected to the EGC in the pedestal which is in turn connected to same in each pedestal and an electrode at each pedestal thus comprising the grounding electrode system. Are you familiar with the Soares Book on Grounding which I have been referring to in my posts? If so, that is what I was taught from, along with MH's book on grounding as well as Tom Henry's. I was taught many moons ago that they all concurred on this aspect of electrical theory and grounding principles. If I have misunderstood please enlighten me with a factual explanation. I am not being a SA here, just really interested in your take. And to answer your question, yes, I do care. Grounding, bonding and touch potential issues have been a very important part of my electrical career, more so probably than most sparkys, as I deal a lot with livestock operations and dairies where the liability is high and engineering scrutiny is intense.


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## amptech (Sep 21, 2007)

Okay, here is a direct quote from Soares 6th Edition, Chapter 6 Grounding Electrodes.
"General. Grounding electrodes provide the essential function of connecting the electrical system to the earth. The earth is considered to be at zero potential. In some cases, the grounding electrode serves to ground the electrical system. In other instances, the electrode is used to connect the noncurrent carrying metallic portions of the electrical equipment to the earth. _*In both situations, the grounding electrode attempts to maintain the electrical equipment at the earth potential present at the grounding electrode.*_"
Where am I going wrong?


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## NolaTigaBait (Oct 19, 2008)

Keyword- attempts. Go read the Mike Holt books. I'm not expert on the subject, but It says that b/c the contact resistance of an electrode to the earth is so high, VERY LITTLE fault current returns to the power supply if the earth is the only fault current return path.


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## amptech (Sep 21, 2007)

NolaTigaBait said:


> Keyword- attempts. Go read the Mike Holt books. I'm not expert on the subject, but It says that b/c the contact resistance of an electrode to the earth is so high, VERY LITTLE fault current returns to the power supply if the earth is the only fault current return path.


Exactly!!! I am not saying now nor have I ever implied in this thread that the grounding electrode has anything to do with clearing a fault. The earth is not an effective conductor back to the source. I am talking about touch potential _*at the electrical equipment*_ which in the instance being discussed in this thread is a campground pedestal. You can connect a 1P 20A circuit breaker directly to a 5/8" x 8' electrode and close the circuit and it will not, 99 out of 100 times, trip the breaker. That isn't what was being discussed in the original subject of the thread. The question was, what would be the function of a grounding electrode installed at each campground pedestal which is fed with multiple circuits or feeders.


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## NolaTigaBait (Oct 19, 2008)

Ok. I was responding to another post. I haven't been following from page 1. We aren't on the same page.:jester:


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## amptech (Sep 21, 2007)

NolaTigaBait said:


> Ok. I was responding to another post. I haven't been following from page 1. We aren't on the same page.:jester:


No problem. I think Brian is assuming the same. I just want to clarify.


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## JohnJ0906 (Jan 22, 2007)

JayH said:


> On the majority of projects I am involved we are required to test and document all grounding electrodes. *We are typically required to meet the NEC standard of 25 ohms.*
> 
> I worked on one facility that required much lower resistance, but I cannot remember exactly how low. It was a military testing facility where all conduit was required to be aluminum rigid.


With the exception of a _single _ground rod, there is no "NEC Standard".
You can be 100% NEC compliant with a 100 ohm CCE.


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## amptech (Sep 21, 2007)

JohnJ0906 said:


> With the exception of a _single _ground rod, there is no "NEC Standard".
> You can be 100% NEC compliant with a 100 ohm CCE.


What is a CCE ?


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## Dennis Alwon (May 9, 2009)

amptech said:


> What is a CCE ?


I think he means CEE concrete encased electrode.


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## brian john (Mar 11, 2007)

Jay I have asked you for evidence of yours not from other sources that quote theory and/or for all voltage distribution systems such as 5 kv and above.

Now with a 208/120 VAC or 240/120 VAC distribution system ground the service per the NEC use two rods obtain what ever ground resistance that is achieved by this method. Now take a solenoid tester and one foot from the electrodes stick one probe in the earth, now test one phase and what do you have? In the majority on cases NOTHING, maybe in good high mineral content soil you may get a movement of the tester BUT in the majority of cases you have zip, zero, nada. And why is this? BECAUSE and soil, earth, the ground beneath your feet is a poor conductor.

If driving an electrode was of major importance for residential (240/120 VAC and/or 208/120 VAC and that is what we were discussing), the code would have a standard all services must meet not one that goes from less than 1 to infinity.


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## brian john (Mar 11, 2007)

amptech said:


> Exactly!!! I. The question was, what would be the function of a grounding electrode installed at each campground pedestal which is fed with multiple circuits or feeders.


And in this case it would be for lightning and over voltage.

It would do NOTHING in regards to step potential. In addition you would be safer if the earth was not grounded at 120 VAC. Which after driving an electrode it would be ungrounded a small distance from the electrode.


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## amptech (Sep 21, 2007)

brian john said:


> And in this case it would be for lightning and over voltage.
> 
> It would do NOTHING in regards to step potential. In addition you would be safer if the earth was not grounded at 120 VAC. Which after driving an electrode it would be ungrounded a small distance from the electrode.


I guess we'll just have to disagree on this. We obviously don't share the same understanding and experience on the subject.
Dennis, I knew he meant CEE. I was being a SA!


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## JayH (Nov 13, 2009)

My original debate was that a grounding electrode's sole purpose is not solely lightning protection, in any system (aside from a lighting arrest system which I do not recall being the case here.)


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## guschash (Jul 8, 2007)

Article 551.76 A,B,C,D. I don't think you need one.


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