2 ground rods

[raider1]

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

 

[ICE]

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.

 

[raider1]

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

 

[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.

 

[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?

 

[jar546]

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

 

[RJJ]

Crystal clear to me!

 

[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.

 

[jar546]

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.

 

[ICE]

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.

 

[ICE]

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.

 

[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.

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?

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.

 

[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.

 

[mjf]

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.

 

[mjf]

I guess I can't edit my posts

 

[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.

 

[ICE]

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).

 

[ICE]

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.

 

[mjf]

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)?

 

[jar546]

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.

 

[Dennis]

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....

 

[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)

 

[mjf]

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.

 

[mjf]

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"