# 2 ground rods



## ICE

> 250.56 Resistance of Rod, Pipe, and Plate Electrodes. A single electrode consisting of a rod, pipe, or plate that does not have a resistance to ground of 25 ohms or less shall be
> 
> augmented by one additional electrode of any of the types specified by 250.52(A)(4) through (A)(8). Where multiple rod,
> 
> pipe, or plate electrodes are installed to meet the requirements of this section, they shall not be less than 1.8 m (6 ft) apart.


How does your jurisdiction treat that code section?  Do they require a second rod whenever a single rod is required?

When I write the correction, I always spell out the word "feet" as in "a minimum 6 feet away from the first rod"

I still get these:


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## TheCommish

most around here drive 2 rod rather than have the meter to properly test the single rod


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## chris kennedy

2 rods here.


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## jar546

For service changes and upgrades or new installations that don't have rebar in the footer, we always see 2 ground rods because of the same reasons stated above.  1) Not many have the equipment necessary to test and 2) Those that do have a hard time getting 25 ohms or less with our soils.

Here is a short story that I will make long.

I was always under the impression that if you had a water pipe that qualified as a grounding electrode, then if you added a rod outside, that was the 2nd electrode IF you could not prove the 25 ohm rule.  In my little head, we had 2 grounding electrodes and since the water pipe was larger and longer and tied into a system underground, it was the main grounding electrode and the single rod added as the supplemental for the 25 ohm rule.  I was corrected in person by Michael Johnston who sits on a few CMPs.

Of course, me being me, I had to question him and I asked:  "So let me get this straight.  If I have a house that has a plastic water main coming in and plastic pipe through out, I have to have 2 ground rods and agree.  But, you are telling me that if I have a metallic water pipe that is considered a grounding electrode, I have to add 2 rods (if I don't meter the one) in addition to the water pipe?".  His answer was "Yes, that is the intent."

I love to learn right from the source when possible.  It make the humbling experience more bearable.


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## ICE

> 250.56 Resistance of Rod, Pipe, and Plate Electrodes.A single electrode consisting of a rod, pipe, or plate *that does not have* a resistance to ground of 25 ohms or less shall be
> 
> augmented by one additional electrode of any of the types specified by 250.52(A)(4) through (A)(8). Where multiple rod,
> 
> pipe, or plate electrodes are installed to meet the requirements of this section, they shall not be less than 1.8 m (6 ft) apart.


How does one know that the electrode does not have less than 25 ohms resistance to ground?  The only way to know is an expensive three point test performed by a recognized agency.

Requiring a second rod is a knee-jerk reaction to a code section.  A ground rod of unknown resistance to ground gets augmented with another rod because there is that possibility that there is more than 25 ohms resistance to ground.  The possibility of a code violation results in not a little bit of effort and expense.

This sounds a lot like a jumper between the hot and cold pipes at the water heater.

Well in principle only because we're talking about a little bit of work and not much expense with the jumper.


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## jwelectric

ICE said:
			
		

> How does your jurisdiction treat that code section?  Do they require a second rod whenever a single rod is required?


 Each and every time. At a temp pole, remote building, service, or any place that a rod, pipe, or plate electrode is installed except as outlined in 250.54. The 2011 cycle cleared this up quite a bit by requiring two rods plain and simple (250.53(A)(2).





			
				ICE said:
			
		

> This sounds a lot like a jumper between the hot and cold pipes at the water heater.


  Bonding of metal water pipes comes from a different part of Article 250 than the installation of electrodes. The bonding of cold to hot metal water pipes is not found in the NEC.


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## Dennis

Even if those rods were 6' apart the installation is not compliant.  The way it is can cause a choke on the grounding electrode conductor.  The metal cable must be bonded to the clamp


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## ICE

Dennis said:
			
		

> Even if those rods were 6' apart the installation is not compliant.  The way it is can cause a choke on the grounding electrode conductor.  The metal cable must be bonded to the clamp


You should have seen the rest of the work.


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## Dennis

ICE said:
			
		

> You should have seen the rest of the work.


Are these guys licensed or are they general contractors that are allowed to do some electrical work


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## ICE

It doesn't take much to get a license in California.  Most of what I see is some guy passing himself off as a licensed electrician.  A lot of it is a general contractor that hires anybody that doesn't have burnt fingers to do electrical work.

This was presented as a water pipe bond.  They were serious.





This had a general contractor behind it.





I had nothing to do with this job until they requested a final inspection.  The job card had approvals through lath.  All that was left was a final.


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## chris kennedy

ICE said:
			
		

> A lot of it is a general contractor that hires anybody that doesn't have burnt fingers to do electrical work.


Any electrician worth his salt I know wears readin glasses, has weathered wrinkled skin, grey hair and whiskers and burnt fingers.

And the best tree killer I know is missing a finger.


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## jar546

Chris, I have a picture of what you are describing

View attachment 744


View attachment 744


/monthly_2013_07/_JAR6808-Edit.jpg.dc2c3a5f9942c89b9ed123a2969641a1.jpg


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## chris kennedy

LOL, yeah walked right into that one. I did get a hair cut.


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## electriclese

Here in Pueblo Colorado we have very dry soil with poor conductivity.  By default the inspectors out here require two 8' rods driven a minimum of 6' apart.


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## RJJ

Dennis: Not sure I understand the comment on choke hold above? please explain?


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## raider1

RJJ said:
			
		

> Dennis: Not sure I understand the comment on choke hold above? please explain?


RJJ,

The metal sheath of the cable armor protecting the grounding electrode conductor must be bonded to the GEC at both ends. (See 250.64(E))

If you do not bond the cable armor and the grounding electrode conductor at both ends effectively making them a parallel path then during a lightning event any current flowing through the GEC would induce counter EMF in the cable armor. The resulting magnetic field will in essence "Choke" the grounding electrode conductor and resist the flow of current through the GEC to the earth. It has been estimated that not bonding both ends of a raceway or cable armor that contain a GEC could result in a 90% choke. The lightning induced currents would then try to find another path to the earth and may damage the electrical system or building.

This only affects ferrous cable armor and raceways, aluminum, stainless steel, red brass and PVC raceways and cable armor need not be bonded.

Chris


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## Dennis

raider1 said:
			
		

> RJJ,The metal sheath of the cable armor protecting the grounding electrode conductor must be bonded to the GEC at both ends. (See 250.64(E))
> 
> If you do not bond the cable armor and the grounding electrode conductor at both ends effectively making them a parallel path then during a lightning event any current flowing through the GEC would induce counter EMF in the cable armor. The resulting magnetic field will in essence "Choke" the grounding electrode conductor and resist the flow of current through the GEC to the earth. It has been estimated that not bonding both ends of a raceway or cable armor that contain a GEC could result in a 90% choke. The lightning induced currents would then try to find another path to the earth and may damage the electrical system or building.
> 
> This only affects ferrous cable armor and raceways, aluminum, stainless steel, red brass and PVC raceways and cable armor need not be bonded.
> 
> Chris


thanks chris-  that's a better explanation then I could have done...


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## RJJ

I have been around too long, but never heard the term Choked in this manner. Learn something new everyday. Thanks to both on the explanation.


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## steveray

"I was corrected in person by Michael Johnston who sits on a few CMPs."

We have a signed copy of his book here in the office....his father still lives in town...Nice man....


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## raider1

Dennis said:
			
		

> thanks chris-  that's a better explanation then I could have done...


Thanks Dennis,

I'm sure your explanation would have been as good as mine.

Chris


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## raider1

ICE said:
			
		

> How does one know that the electrode does not have less than 25 ohms resistance to ground? * The only way to know is an expensive three point test performed by a recognized agency. * Requiring a second rod is a knee-jerk reaction to a code section.  A ground rod of unknown resistance to ground gets augmented with another rod because there is that possibility that there is more than 25 ohms resistance to ground.  The possibility of a code violation results in not a little bit of effort and expense.
> 
> This sounds a lot like a jumper between the hot and cold pipes at the water heater.
> 
> Well in principle only because we're talking about a little bit of work and not much expense with the jumper.


Does your jurisdiction require a 3rd party test?

I allow the electrical contractor to perform the test if they have the proper equipment.

Chris


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## ICE

raider1 said:
			
		

> Does your jurisdiction require a 3rd party test?I allow the electrical contractor to perform the test if they have the proper equipment.
> 
> Chris


It has to be done by an approved agency.


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## raider1

ICE said:
			
		

> It has to be done by an approved agency.


Wow, is that a State rule or a local rule?

I can understand requiring an approved agency to perform the required performance test of a GFPE equipment in 230.95© but a simple ground resistance test to comply with 250.53(A)(2) Exception should be able to be done by an electrical contractor with the proper meter.

Chris


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## Dennis

IMO, it is not worth the time or money to drive one rod and try and prove 25ohms.  In fact around here it just won't happen and even if it were possible I would waste more time proving it then the job would be worth.  If you don't use the concrete encased electrode then we just drive 2 rods and be done with it.  Can't imagine getting an outside agency to do that


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## raider1

Dennis said:
			
		

> IMO, it is not worth the time or money to drive one rod and try and prove 25ohms.  In fact around here it just won't happen and even if it were possible I would waste more time proving it then the job would be worth.  If you don't use the concrete encased electrode then we just drive 2 rods and be done with it.  Can't imagine getting an outside agency to do that


I agree 100%.

Chris


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## ICE

raider1 said:
			
		

> Wow, is that a State rule or a local rule?I can understand requiring an approved agency to perform the required performance test of a GFPE equipment in 230.95© but a simple ground resistance test to comply with 250.53(A)(2) Exception should be able to be done by an electrical contractor with the proper meter.
> 
> Chris


It is a local rule.  The test is not one of the hand held meters.  It is a three point test.  I have seen it done one time, years ago.  That was a demonstration by a test lab.


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## raider1

ICE said:
			
		

> It is a local rule.  The test is not one of the hand held meters.  It is a three point test.  I have seen it done one time, years ago.  That was a demonstration by a test lab.


I know it is a 3 point test, I happen to have a 3 point fall of potential meter. So you would not let me test my ground rod but make me hire a test lab?

Chris


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## jar546

We accept a printout from the contractor if they want to do that which is very rare.  I was given a verbal once by a large commercial contractor and said to give me the printout. They said their machine does not have printing capability so I said I will need to witness it (such BS for a single rod).  Anyway, the guy brought out a Fluke 23 and some leads.  I told him nevermind, just put in another rod.


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## mjf

Please enlighten me, as I'm having a hard time understanding the controversy of driving 1 or 2 groundrods.

250.56 Resistance of Rod, Pipe, and Plate Electrodes.

A single electrode consisting of a rod, pipe, or plate that does not have a resistance to ground of 25 ohms or less shall be

augmented by one additional electrode of any of the types specified by 250.52(A)(4) through (A)(8). Where multiple rod,

pipe, or plate electrodes are installed to meet the requirements of this section, they shall not be less than 1.8 m (6 ft) apart.

Either test and prove the ohms or supply 2 grounding electrodes, this code seems to be EXTREMELY clearly written.

I install 1 groundrod to supplement my primary grounding electrode (whether it is another groundrod, a rod, a pipe, or a plate) because that is what the code requires.

Always passes inspection.  Shouldn't it?


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## jar546

mjf, you seem to have an understanding and are doing it right.


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## RJJ

Crystal clear to me!


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## jwilly3879

I don't do the electrical inspections in my jurisdiction, they are done by a third party. The third party requires (2) - 8 ft rods, at least 6 ft apart with the gec forming a loop from the panel to the 1st rod then to the 2nd rod and back to the panel. That is what they ask for and everyone around here does it that way.


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## jar546

jwilly3879 said:
			
		

> I don't do the electrical inspections in my jurisdiction, they are done by a third party. The third party requires (2) - 8 ft rods, at least 6 ft apart with the gec forming a loop from the panel to the 1st rod then to the 2nd rod and back to the panel. That is what they ask for and everyone around here does it that way.


OK, I am a bit lost on whoever interpreted that.


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## ICE

jwilly3879 said:
			
		

> I don't do the electrical inspections in my jurisdiction, they are done by a third party. The third party requires (2) - 8 ft rods, at least 6 ft apart with the gec forming a loop from the panel to the 1st rod then to the 2nd rod *and back to the panel*. That is what they ask for and everyone around here does it that way.


Oh crap! I think I like that idea.


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## ICE

raider1 said:
			
		

> I know it is a 3 point test, I happen to have a 3 point fall of potential meter. So you would not let me test my ground rod but make me hire a test lab?Chris


That is correct.  Sorry about that.  Please don't take this as a reflection on you but the test is complicated enough and can involve such a huge area that we can't let just anyone with the money to buy the equipment do the test.  A false reading is easy to come by and it takes a person with the right training and experience to perform the test.


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## mjf

Uh oh.......now I'm more confused.... how can these both be correct???

Here is a short story that I will make long.

I was always under the impression that if you had a water pipe that qualified as a grounding electrode, then if you added a rod outside, that was the 2nd electrode IF you could not prove the 25 ohm rule.  In my little head, we had 2 grounding electrodes and since the water pipe was larger and longer and tied into a system underground, it was the main grounding electrode and the single rod added as the supplemental for the 25 ohm rule.

I was corrected in person by Michael Johnston who sits on a few CMPs.  [/color]Of course, me being me, I had to question him and I asked:  "So let me get this straight.  If I have a house that has a plastic water main coming in and plastic pipe through out, I have to have 2 ground rods and agree.  But, you are telling me that if I have a metallic water pipe that is considered a grounding electrode, I have to add 2 rods (if I don't meter the one) in addition to the water pipe?".  His answer was "Yes, that is the intent."

I love to learn right from the source when possible.  It make the humbling experience more bearable.



			
				mjf said:
			
		

> Please enlighten me, as I'm having a hard time understanding the controversy of driving 1 or 2 groundrods.  250.56 Resistance of Rod, Pipe, and Plate Electrodes.
> 
> A single electrode consisting of a rod, pipe, or plate that does not have a resistance to ground of 25 ohms or less shall be
> 
> augmented by one additional electrode of any of the types specified by 250.52(A)(4) through (A)(8). Where multiple rod,
> 
> pipe, or plate electrodes are installed to meet the requirements of this section, they shall not be less than 1.8 m (6 ft) apart.
> 
> Either test and prove the ohms or supply 2 grounding electrodes, this code seems to be EXTREMELY clearly written.
> 
> I install 1 groundrod to supplement my primary grounding electrode (whether it is another groundrod, a rod, a pipe, or a plate) because that is what the code requires.
> 
> Always passes inspection.  Shouldn't it?





			
				jar546 said:
			
		

> mjf, you seem to have an understanding and are doing it right.


 We can't both be right.  If the "intent" is to have 2 supplemental electrodes, the code should reflect that.


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## ICE

I've witnessed plenty of discussions here where everybody is right...just ask them.

The intent of the code is to have one supplemental electrode if a water pipe is being used as an electrode.  Now if a driven rod is chosen as the supplemental electrode, the code states that the resistance to ground can't exceed 25 ohms.  If the resistance to ground does exceed 25 ohms, the code states that another electrode shall be provided.

Because nobody can discern the resistance to ground without an expensive test, by default a second rod is always required.  The code does not expressly state that two rods are always required but the code backs you into a corner where you come to that conclusion on your own.


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## mjf

ICE said:
			
		

> I've witnessed plenty of discussions here where everybody is right...just ask them.The intent of the code is to have one supplemental electrode if a water pipe is being used as an electrode.
> 
> I must respectfully disagree, the code states that if ANY of the specified "primary" electrodes don't bring resistance under 25 ohms, a secondary (or supplemental) electrode must be provided.
> 
> Now if a driven rod is chosen as the supplemental electrode, the code states that the resistance to ground can't exceed 25 ohms.  If the resistance to ground does exceed 25 ohms, the code states that another electrode shall be provided.
> 
> Again, I disagree, unless you meant primary where you said supplemental.
> 
> Because nobody can discern the resistance to ground without an expensive test, by default a second rod is always required.  The code does not expressly state that two rods are always required but the code backs you into a corner where you come to that conclusion on your own.


ONE (specified) primary electrode and ONE secondary electrode required.


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## mjf

I guess I can't edit my posts


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## Dennis

It does not matter whether the pipe coming in is plastic or metal.  In either case you still need 2 ground rods unless you can show 25 ohms with one rod.  That is not possible around here so two rods are used.  There are probably few areas where 25 ohms are gotten with one rod and if the test is done when the ground is wet then I bet you don't get 25 ohms when it is dry.


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## ICE

mjf said:
			
		

> I guess I can't edit my posts


There is a way to fix that.



> I must respectfully disagree, the code states that if ANY of the specified "primary" electrodes don't bring resistance under 25 ohms, a secondary (or supplemental) electrode must be provided.





> 250.56 Resistance of *Rod, Pipe, and Plate* Electrodes. Asingle electrode consisting of a rod, pipe, or plate that does not
> 
> have a resistance to ground of 25 ohms or less shall be
> 
> augmented by one additional electrode of any of the types
> 
> specified by 250.52(A)(4) through (A)(8). Where multiple rod,
> 
> pipe, or plate electrodes are installed to meet the requirements
> 
> of this section, they shall not be less than 1.8 m (6 ft) apart.
> 
> FPN: The paralleling efficiency of rods longer than 2.5 m (8
> 
> ft) is improved by spacing greater than 1.8 m (6 ft).


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## ICE

Dennis said:
			
		

> There are probably few areas where 25 ohms are gotten with one rod and if the test is done when the ground is wet then I bet you don't get 25 ohms when it is dry.


Many years ago I worked for a company that manufactured high vacuum deposition equipment.  The machine blasted a gold ingot under a vacuum with an electron beam(100,000 volts).  That turned the gold ingot into a bunch of gold molecules.  The molecules stuck to silicon wafers that were then used to make computer chips.  The controls for this equipment were sensitive in the extreme.  If things went awry the result could be an explosion.  It did happen and it was deadly.

I think it was Sun Microsystems that had these machines and developed a problem where they lost control of the equipment.  The problem was solved with a garden hose and a constant stream of water on the grounding electrode.


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## mjf

Dennis said:
			
		

> It does not matter whether the pipe coming in is plastic or metal.  In either case you still need 2 ground rods unless you can show 25 ohms with one rod.  That is not possible around here so two rods are used.  There are probably few areas where 25 ohms are gotten with one rod and if the test is done when the ground is wet then I bet you don't get 25 ohms when it is dry.


Trying to clarify.  You are stating that a metal pipe does not count as 1 of the 2 grounding electrodes required (in lieu of the resistance test)?


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## jar546

mjf said:
			
		

> Trying to clarify.  You are stating that a metal pipe does not count as 1 of the 2 grounding electrodes required (in lieu of the resistance test)?


I can't answer for Dennis but Yes, that is correct.  Whether you have a water pipe or not, 2 rods are required in lieu of a resistance test.


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## Dennis

jar546 said:
			
		

> I can't answer for Dennis but Yes, that is correct.  Whether you have a water pipe or not, 2 rods are required in lieu of a resistance test.


Well you did answer as I would have,  so thanks....


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## jwelectric

There is no such thing as a primary electrode. There are eight items mentioned in 250.52 and should any of those be present they must be bonded together to make the electrode system. No matter how many or of what type electrodes are used there will always be one electrode system.

An electrode system does not have primary and secondary electrodes. When it comes to rod, pipe, and plate electrodes they must have a resistance of 25 ohms or less or be augmented or supplemented by one of the other electrodes outlined in 250.52 except a metal water pipe.

A metal water pipe cannot be used alone as an electrode. It must be used with one of the other seven. Should a rod, pipe or plate electrode be used with a water pipe then that rod, pipe, or plate electrode by itself must have 25 ohms or less of resistance or have another electrode to go with it.

See 250.53(A)(2) and (D)(2)


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## mjf

jar546 said:
			
		

> I can't answer for Dennis but Yes, that is correct.  Whether you have a water pipe or not, 2 rods are required in lieu of a resistance test.


OK, I'll assume my confusion is in a change from 2008 to 2011....I'm still on the 2008 which allows a metal water pipe and 1 additional electrode in lieu of a resistance test.


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## mjf

jwelectric said:
			
		

> There is no such thing as a primary electrode. There are eight items mentioned in 250.52 and should any of those be present they must be bonded together to make the electrode system. No matter how many or of what type electrodes are used there will always be one electrode system. An electrode system does not have primary and secondary electrodes. When it comes to rod, pipe, and plate electrodes they must have a resistance of 25 ohms or less or be augmented or supplemented by one of the other electrodes outlined in 250.52 except a metal water pipe.
> 
> A metal water pipe cannot be used alone as an electrode. It must be used with one of the other seven. Should a rod, pipe or plate electrode be used with a water pipe then that rod, pipe, or plate electrode by itself must have 25 ohms or less of resistance or have another electrode to go with it.
> 
> See 250.53(A)(2) and (D)(2)


I apologize, I am aware that there are no "primary" and "secondary" grounding electrodes... that's why I put them in "quotes"


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## jar546

mjf said:
			
		

> OK, I'll assume my confusion is in a change from 2008 to 2011....I'm still on the 2008 which allows a metal water pipe and 1 additional electrode in lieu of a resistance test.


I am talking about the 2008.  Makes no difference 08 or 11

I was schooled on this in 2009 by Mr. Johnston


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## Dennis

mjf said:
			
		

> OK, I'll assume my confusion is in a change from 2008 to 2011....I'm still on the 2008 which allows a metal water pipe and 1 additional electrode in lieu of a resistance test.


I think this is where your problem lies. Black bold in art. 250.53(D)(2) below tells us we must have one additional electrode for a water pipe-- don't stop there.  The reddish brown part states that if the extra electrode is a rod, pipe or plate then it must comply with 250.53(A).  Art. 250.53(A)(2) below (the blue part) says that a single rod must be supplemented by another rod or....

The green states one rod is fine if we get 25 ohms--- only if one rod gets 25 ohm may we ignore the second rod.  Hope this helps



> 250.53(D)(2)(2) Supplemental Electrode Required. *A metal underground water pipe shall be supplemented by an additional electrode *of a type specified in 250.52(A)(2) through (A)(8). If the supplemental electrode is of the* rod, pipe, or plate type, it shall comply with 250.53(A*). The supplemental electrode shall be bonded to one of the following:
> 
> (1) Grounding electrode conductor
> 
> (2) Grounded service-entrance conductor
> 
> (3) Nonflexible grounded service raceway
> 
> (4) Any grounded service enclosure
> 
> (5) As provided by 250.32(B)





> 250.53(A) Rod, Pipe, and Plate Electrodes. Rod, pipe, and plate electrodes shall meet the requirements of 250.53(A)(1) through (A)(3).
> 
> (1) Below Permanent Moisture Level. If practicable, rod, pipe, and plate electrodes shall be embedded below permanent moisture level. Rod, pipe, and plate electrodes shall be free from nonconductive coatings such as paint or enamel.
> 
> (2) Supplemental Electrode Required. *A single rod, pipe, or plate electrode shall be supplemented by an additional electrode *of a type specified in 250.52(A)(2) through (A)(8). The supplemental electrode shall be permitted to be bonded to one of the following:
> 
> (1) Rod, pipe, or plate electrode
> 
> (2) Grounding electrode conductor
> 
> (3) Grounded service-entrance conductor
> 
> (4) Nonflexible grounded service raceway
> 
> (5) Any grounded service enclosure
> 
> *Exception: If a single rod, pipe, or plate grounding electrode has a resistance to earth of 25 ohms or less, the supplemental electrode shall not be required.*


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## mjf

Thanks Dennis.

Right after I hit enter, I pulled out my code book and dug into those sections.


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