Extra/Auxilary grounding rods..... Don't do it.

[FilterGuy]

Another nice video from Mike Holt.

Auxilary grounding rods are not required but there is a rule that states there are no requirements on an auxiliary ground e;ectrodes. At one point in the video, he talks about CAT 5 wires and 10 penny nails for the auxiliary grounding electrode.


It has taken several years but we are starting to see both professionals and DIYrs wake up to the fact that auxiliary grounding electrodes are 1) not required and 2) not recommended.

Having said that, I am still a little uncomfortable with the code requirement for a second (not auxiliary) grounding electrode for separate buildings. I would love to see the rationale for this as well as a multi-year study of a bunch of instances where this is not done. The good news is that with just a little planning the 2nd electrode can be set up with the path to the first electrode only going through breaker boxes....but even breaker boxes are starting to get a lot of electronics in them.

 

[timselectric]

Having said that, I am still a little uncomfortable with the code requirement for a second (not auxiliary) grounding electrode for separate buildings.

I don't like it, either.
The best I can get from anyone is that the electricity is used at the separate building. And they think that it's safer to make sure that the local earth is functionally bonded to the source.

 

[marionw]

There are two issues here; Neutral/Ground (N/G) bonding and Ground/Ground bonding.
There should only be ONE Neutral/Ground (N/G) bond and it is at the main panel or grid/service entrance.
You can have multiple ground to ground bonds. If you have a grounding electrode at a PV Array for non conducting exposed metal, the ground is also carried back to the main ground which may be the ONE N/G ground bond or simply connected to the main grounding electrode.
If there is a ground electrode at a separate building there is NO N/G bond in the panel at that separate building. There would be two bus bars in the subpanel, one for the neutral and one for the ground and they would not be bonded.

 

[timselectric]

You can have multiple ground to ground bonds. If you have a grounding electrode at a PV Array for non conducting exposed metal, the ground is also carried back to the main ground

This is not required or recommended. And what we are trying to get people to avoid.
Only the EGC is required.

If there is a ground electrode at a separate building there is NO N/G bond in the panel at that separate building. There would be two bus bars in the subpanel, one for the neutral and one for the ground and they would not be bonded.

With or without the extra ground rod.
It's still a sub panel and the neutral and ground must be separated.

 

[DPC]

When I build a switch room I bring in 1 4/0 ground to bond all my non current carrying metal and the XO to the system ground.
My cables also carry a bond wire so am effectively grounding only once but I have multiple bonds even the doors have bonds.

I have seen some guys add a bond to a pump on a machine base.
This doesn't need to be done because the cable carries a bond conductor.
Above 600 volts then its mandatory to double bond this way.
A pump like a submersible thats on a plug at 600 volts will require an external solid bond if not equipped with a ground check system to verify grounds.

I like to bond the rack and splitter for a pump if located away from the switch room and near a submersible pump.
Just in case of a local touch potential.

So its common to find AUX grounds all over the place if there is a reasons for it like a distributed power system or people scared of local touch potentials because of water or high voltage.
But as said before you only gound XO once or your service neutral on a residential.

 

[740GLE]

With or without the extra ground rod.
It's still a sub panel and the neutral and ground must be separated.

You repeated his exact same comment.

 

[timselectric]

You repeated his exact same comment.

No
They said

If there is a ground electrode at a separate building

I said that it didn't have anything to do with if there was a local ground rod.

 

[wattmatters]

Our two outbuildings have their own ground rod. Standard practice here.

 

[FilterGuy]

Our two outbuildings have their own ground rod. Standard practice here.

Yup.... that is code and it has been the code for a long time. But no one has given me an explanation of why the code requires it. I like it a lot better when I understand the rationale behind the rules.

 

[hwy17]

I like 3 wire outbuilding services with the outbuilding having it's own main panel, bond, and ground rod.

I know they were disallowed by the NEC for open neutral risk, but I'm a lot more worried about my service drop from the utility going open neutral since it's literally hanging on it's neutral wire. Compared to an outbuilding service in conduit

I guess maybe the logic is that the outbuilding is more likely to suffer an open neutral in the process of someone doing work on the main house system.

 

[marionw]

The vide at the top represents NEC 2023.
The three largest counties in South Carolina (Charleston, Greenville and Spartanburg) all have adopted the 2020 National Electrical Code (with modifications). The NEC is generally considered the minimum requirements and AHJ's will often add additional requirements, often at the request of major builders/construction companies in the state (politics).

Folks can quote the NEC all day long but at the end it is still the AHJ and the inspector that have to be satisfied. It might be easier to just install the ground rod and move on.

 

[timselectric]

Yup.... that is code and it has been the code for a long time. But no one has given me an explanation of why the code requires it. I like it a lot better when I understand the rationale behind the rules.

It's changed over the years.
When I first started, no ground to the outbuildings.
Then, they added the ground rod requirement. (No EGC)
Then, they required either an EGC or a ground rod. But not both, as that was a violation.
Now, both are required.
Like everything else, the trend is towards the EGC only. Just have to hang on for a few more code cycles.
The rationale is "that's what we've always done" , versus "oh crap we had no idea how stupid that was".

 

[timselectric]

I like 3 wire outbuilding services with the outbuilding having it's own main panel, bond, and ground rod.

Omitting the EGC, omits the grounding system.
And relies on the neutral (a current carrying conductor) to also be the effective fault current path.
This is dangerous. because if the neutral is lost , so is the fault current path. While there are still live conductors that could be in a fault condition.

 

[hwy17]

Omitting the EGC, omits the grounding system.
And relies on the neutral (a current carrying conductor) to also be the effective fault current path.
This is dangerous. because if the neutral is lost , so is the fault current path. While there are still live conductors that could be in a fault condition.

Can you describe an example location of this fault current?

The way I see it for the outbuilding, it works like a regular house service, the panel is bonded so everything inside has an EGC for fault current to get back to the neutral on.

Is this about fault currents in the supply conduit? I don't see how those wouldn't clear either.

And don't get me wrong, I'm not smarter than everyone who writes the code, I would wire a new install with 4 wire. I just have an old install from the 3 wire era and I like it.

 

[timselectric]

Can you describe an example location of this fault current?

L1, or L2 shorted to anything metal that can be touched by people.
Conduit
Junction box
Metal framing
metal siding on a metal barn.
The metal case of any equipment that is plugged in.

Also with the extra ground rod, and wet earth.
A lost neutral without a grounding system, creates a potential step Hazzard between ground rods.

 

[Zwy]

Yup.... that is code and it has been the code for a long time. But no one has given me an explanation of why the code requires it. I like it a lot better when I understand the rationale behind the rules.

Over on the Mike Holt forums, there has been discussion about this topic a few times. No consensus and usually those advocating using a ground rod at each structure just repeat lightning is the reason. I've read a few of the recent threads and think over time the ground rod requirement may be dropped in NEC.

I think is the reason it still is in the code is due to past years when the EGC was not ran in a feeder circuit to another building. Bonding needed to be done at the panel at the end of the feeder circuit. This required a ground rod. Thus the practice has been carried over after adoption of running an EGC with the current carrying conductors on a feeder circuit. Think of all the stray voltage created out there with the bonding at each structure after a main service.

The only other reason I can think of is possibly long runs on a feeder and getting voltage potential to a minimum. Environmental factors (wind for example) can create some buildup of voltage potential that needs to be dissipated.

 

[Zwy]

Can you describe an example location of this fault current?

The way I see it for the outbuilding, it works like a regular house service, the panel is bonded so everything inside has an EGC for fault current to get back to the neutral on.

Is this about fault currents in the supply conduit? I don't see how those wouldn't clear either.

And don't get me wrong, I'm not smarter than everyone who writes the code, I would wire a new install with 4 wire. I just have an old install from the 3 wire era and I like it.

In the old 3 wire feeders, you had some voltage gradient from the second panel bonding thru the ground. This was discovered on dairy farms when cows would have low production and had health problems. Stray voltage was huge problem back in the 3 wire feeder days, many dairy farmers went bankrupt due to it.

 

[hwy17]

L1, or L2 shorted to anything metal that can be touched by people.
Conduit
Junction box
Metal framing
metal siding on a metal barn.
The metal case of any equipment that is plugged in.

Also with the extra ground rod, and wet earth.
A lost neutral without a grounding system, creates a potential step Hazzard between ground rods.

But this is my fault current path inside the outbuilding. It rides the outbuilding EGC onto the neutral and the neutral back to the source.

Now faults that happen in between House and Outbuilding gets more complicated. I am used to it being PVC conduit. If it was metal conduit that would complicate things. I don't even know how they 3 wire subpanels with metal conduit, the metal would carry regular neutral current. Maybe you're talking about these complexities in between.

 

[timselectric]

But this is my fault current path inside the outbuilding. It rides the outbuilding EGC onto the neutral and the neutral back to the source.

Not if that neutral is lost.
The grounding system should be separated from any current carrying conductors.
Only shared by the neutral on the service conductor. (Ahead of the first means of disconnect)

 

[hwy17]

Not if that neutral is lost.

Yes open neutral faults. But it seems so much more likely to me that the messenger wire on my triplex service drop will snap one day compared to anything happening to my outbuilding neutral in conduit.