Shed Sub panel 2 rods or 1

[roger]

Going with the mentality "just put one in and get done with it" may not make a financial sense if the project is multi tract home project.

Well let's forget the fact that your inspectors are accepting one rod, your argument about the multi track project would still be more expensive if you are going test each rod.

Besides the initial expense of the test set, the labor to correctly test each rod would be more than adding a rod. At times we have to test for performance grounding and by the time you start breaking out the test set, perform a number of tests for an average, log the results, put everything up, and get in the truck, it would have been much less expense to simply drive a second rod.

Roger

 

[iwire]

Maybe I should have mentioned it earlier that the local AHJ has done extensive testing throughout the city and determined the 2nd rod is not required.

Is there an amendment to the NEC?

If not it's getting two rods from me.

 

[K8MHZ]

If the AHJ accepts one rod without testing that's great. The NEC requires two rods or the testing.

Just guessing, but it have something to do with the rarity of lightning strikes in the area.

 

[iwire]

Just guessing, but it have something to do with the rarity of lightning strikes in the area.

I don't think there is a chance that is the reason.

I would bet it has more to do with tradition.

 

[kwired]

Just guessing, but it have something to do with the rarity of lightning strikes in the area.

I thought that may have some contribution, as well as possibly average annual rainfall along with soil conditions.

Did a check on line found a site that tells weather data for different areas, SF averaged 23.5 inches of rain annually. A little less then we get where I live, but still somewhat moderate compared to many places I did look at. I found Las Vegas to be lowest of what I looked up at only a little over 4 inches, Phoenix at 8 inches, Colorado Springs at 16.5, Oklahoma City at 36.5 Boston at 43.5 and Miami at 62 inches.

You still need to look at soil conditions to some degree but moisture levels will make a difference on the resistance of an electrode.

 

[Little Bill]

Our inspectors only require one rod at a garage/shed/building on same property as dwelling. The dwelling gets two rods though.

 

[K8MHZ]

I thought that may have some contribution, as well as possibly average annual rainfall along with soil conditions.

Did a check on line found a site that tells weather data for different areas, SF averaged 23.5 inches of rain annually. A little less then we get where I live, but still somewhat moderate compared to many places I did look at. I found Las Vegas to be lowest of what I looked up at only a little over 4 inches, Phoenix at 8 inches, Colorado Springs at 16.5, Oklahoma City at 36.5 Boston at 43.5 and Miami at 62 inches.

You still need to look at soil conditions to some degree but moisture levels will make a difference on the resistance of an electrode.

We get 33.5 inches per year, average. A single electrode in my area is 1000 ohms, some close to 1300 ohms. The reason is we are pretty much sitting on dune sand.

 

[Ponchik]

Well let's forget the fact that your inspectors are accepting one rod, your argument about the multi track project would still be more expensive if you are going test each rod.

Besides the initial expense of the test set, the labor to correctly test each rod would be more than adding a rod. At times we have to test for performance grounding and by the time you start breaking out the test set, perform a number of tests for an average, log the results, put everything up, and get in the truck, it would have been much less expense to simply drive a second rod.

Roger

If it is not required, then we don't test it nor put one in.

Then again as I had mentioned before if it is required by AHJ or testing is required then put one in don't argue with AHJ.

 

[goldstar]

While what you suggests makes sense you cannot use the service grounding electrodes to supplement a single rod at a remote building.

You must use new electrodes.

OK, I stand corrected. I don't want to pirate this thread from the OP but if anyone knows the logical reasoning behind the CMP requiring the installation of the second rod in this instance (aside from "cause that's what the Code says") I'd like to hear it.

 

[jaggedben]

The AHJ is correct, the single rod would have to be 25 ohms or it would not be considered a supplemental GE, see 250.53(D)(2), the supplemental GE must meet the requirements of 250.53(A)(2) which would mean two rods or bring out a test set

Roger

As Roger stated the AHJ is correct. A single rod is not an electrode if it cannot pass the 25 ohms or less test. Two rods are considered an electrode no testing required.

Okay, either I'm really not following your argument, or maybe you guys just didn't read my post carefully.

This AHJ requires 3 electrodes in all cases (unless there's a verified UFER): water pipe, 1st rod, 2nd rod. You don't get to not drive the 2nd ground rod if the water is done and good.

Is that what you guys think the NEC requires? Because I see 250.3 saying: "A single rod, pipe, or plate electrode shall be supplemented..." and the water pipe is already a single pipe electrode. It does not say that the supplemental electrode needs another supplemental electrode!

I think the AHJ's logic may be that they can't verify that the water pipe meets the requirements of an electrode, so you don't get to count it, but you have to bond it because of 250.50 just in case it does count. :roll: In any case, I know I'm not changing their minds.

We have another AHJ that lets us have either <water+one rod> or <two rods>. I think this is correct except for the fact that the water pipe is required to be bonded if it meets the requirements of an electrode. But I'm grateful for their interpretation on existing houses.

Is the second rod such a big deal it's worth spending time on an Internet forum to figure out a way around using one?

When you're trying to get done 10 jobs a week and most of the houses in your city have no dirt around them, rock underneath, and/or one rod already driven, it would sure be helpful. I'm sure others mileage will vary.

 

[ActionDave]

Okay, either I'm really not following your argument, or maybe you guys just didn't read my post carefully.

This AHJ requires 3 electrodes in all cases (unless there's a verified UFER): water pipe, 1st rod, 2nd rod. You don't get to not drive the 2nd ground rod if the water is done and good.

Is that what you guys think the NEC requires? Because I see 250.3 saying: "A single rod, pipe, or plate electrode shall be supplemented..." and the water pipe is already a single pipe electrode. It does not say that the supplemental electrode needs another supplemental electrode!
.

Start with the water pipe-

250.53(D) Metal Underground Water Pipe. If used as a ground-
ing electrode, metal underground water pipe shall meet the
requirements of 250.53(D)(1) and (D)(2).

(1) blah, blah, blah.

(2) Supplemental Electrode Required. A metal under-
ground 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).

So when you bounce back up to 250.53(A)

250.53(A)
(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)

you see that they left out the water pipe as a one of the options to supplement a ground rod.

So..... if you have a water pipe and don't have building steel or a ufer you are going to drive a ground rod to meet the requirements of 250.53(D)(2), but now that ground rod has to meet the requirements of 250.53(A)(2), and the easiest way to do that is drive a second rod.

 

[roger]

Okay, either I'm really not following your argument, or maybe you guys just didn't read my post carefully.

I read it and your inspector is correct.

This AHJ requires 3 electrodes in all cases (unless there's a verified UFER): water pipe, 1st rod, 2nd rod. You don't get to not drive the 2nd ground rod if the water is done and good.

He is only requiring two electrodes. You're not seeing the fact that one rod is not an electrode unless you prove it is 25 ohms or less.

Is that what you guys think the NEC requires?

Yes

Because I see 250.3 saying: "A single rod, pipe, or plate electrode shall be supplemented..." and the water pipe is already a single pipe electrode.

The water Pipe electrode must be supplemented by a second electrode and one rod does not qualify

It does not say that the supplemental electrode needs another supplemental electrode!

I agree

I think the AHJ's logic may be that they can't verify that the water pipe meets the requirements of an electrode, so you don't get to count it,

And that may be the reason

but you have to bond it because of 250.50 just in case it does count.

You have to bond it because of 250.104(A)

We have another AHJ that lets us have either <water+one rod> or <two rods>.

That's his prerogative but if the water qualifies as a GEC he is not enforcing the NEC rule.

I think this is correct except for the fact that the water pipe is required to be bonded if it meets the requirements of an electrode.

If it's a metallic water system inside the building it has to be bonded period see the aforementioned 250.104(A)

Roger

 

[goldstar]

Is the second rod such a big deal it's worth spending time on an Internet forum to figure out a way around using one?

I ask this generically, not aimed specifically at the OP. I have seen several threads posted by people trying to get out of driving a second rod.

To me, they end up spending more time (time is money) trying to get out of pounding a rod than they would have in doing it.

Every EC I have worked for put in two rods and spares the hassle of trying not to.

No one is trying to "get around" this Code issue but, you are correct. The easiest way "around" the discussion of this issue is to just spend the $12.00 + a few minutes time, install a second rod and be done with it. However, if we took that attitude with all Code issues we wouldn't have anything to discuss here in the Forum. You could pose a question, get one answer with a Code reference from the Vatican and it's over. But, you can see from the responses that there are varying Code interpretations from other parts of the country that do not agree with what is written The NEC. One township's EI may allow one rod but move one town over and that EI requires 2 rods. I believe now that two rods is the proper way to address this issue only because that is what is written. I think the logic behind it is a crock.

 

[kwired]

OK, I stand corrected. I don't want to pirate this thread from the OP but if anyone knows the logical reasoning behind the CMP requiring the installation of the second rod in this instance (aside from "cause that's what the Code says") I'd like to hear it.

Is possible they have never had this discussion come up? IDK, just speculation. If they did they obviously had decided to leave things as they are for some reason.

The way code is written you don't look at what an adjacent building/structure has for grounding electrodes when considering what to install in your current separate building/structure.

It is fairly clear the GES requirements for each separate building are the same, only difference is you connect it to the grounded conductor at a service supplied structure and to the EGC at a feeder supplied structure.

In fact with multiple tenants and a situation where multiple services are allowed on same building, you still need to treat each space like it were a stand alone building and install a complete GES per code at each tenant space.

 

[K8MHZ]

I believe now that two rods is the proper way to address this issue only because that is what is written. I think the logic behind it is a crock.

Where we are, Western Michigan, the soil is basically sand. One of my friends has been an electrical inspector for decades. At one time they did a test here and showed that one rod was 1000-1300 ohms and adding a second rod only got the system down to 300-600 ohms. He openly admitted that the only reason he made us drive two rods is because that's what the rules said and his job was to be sure the people followed the rules.

The move to requiring a Ufer in new construction is a good one. A concrete encased electrode will actually create a decent connection to the earth, even in sandy soil.

 

[jaggedben]

... you see that they left out the water pipe as a one of the options to supplement a ground rod. ...

Got it. Thanks. That was too subtle for my initial reading. :blink:

 

[goldstar]

you see that they left out the water pipe as a one of the options to supplement a ground rod.

Just to clarify and make sure we're all on the same page, the ground rods are the supplement to the water main ground. And, if you have a CEE you don't need the rods.

 

[petersonra]

The move to requiring a Ufer in new construction is a good one. A concrete encased electrode will actually create a decent connection to the earth, even in sandy soil.

and that is beneficial in what way as opposed to a connection that has somewhat higher impedance?

think carefully before answering as to why a 25 Ohm connection is Ok if you have one rod as your GES, but a 1000 Ohm connection is fine if you have two rods as your GES.

 

[K8MHZ]

and that is beneficial in what way as opposed to a connection that has somewhat higher impedance?

think carefully before answering as to why a 25 Ohm connection is Ok if you have one rod as your GES, but a 1000 Ohm connection is fine if you have two rods as your GES.

Personally, I don't think a near 1000 ohm connection is fine. It's a code minimum. We put in rods because we are allowed to and the customer doesn't care about a good connection to ground. At least a CEE works.

None of the above relates to whether or not an earth connection is good, bad or otherwise. It's just that two rods have been shown to be nearly ineffective in our area, but we have to use them anyway. If we are bound by code to use an earthing electrode, at least it should be one that has been shown to be effective.

 

[iwire]

Personally, I don't think a near 1000 ohm connection is fine. It's a code minimum. We put in rods because we are allowed to and the customer doesn't care about a good connection to ground. At least a CEE works.

None of the above relates to whether or not an earth connection is good, bad or otherwise. It's just that two rods have been shown to be nearly ineffective in our area, but we have to use them anyway. If we are bound by code to use an earthing electrode, at least it should be one that has been shown to be effective.

For the average homeowner that is not into ham radio what benfit is provided by a good connection to dirt?