AHJ Grounding Electrode Requirement

[Rick Christopherson]

Well true and I forget that not everyone is on a Y system as many are on delta local sub feeds, I need to remember this, but in my area our MGN is a Y and I think Don is also as to why his response, but even with a delta system you will still have a MGN using a ziz-zag tie which should not cause a problem being bonded to the secondary neutral to the dwelling.

It is easy to get lost in the slangs each areas might use.

I don't think you understand the question. Are you suggesting that your POCO is setting up their single-phase customers with non-seperately-derived-systems? Is there an electrical connection between the primary-winding to secondary-winding of their transformers?

 

[hurk27]

I don't think you understand the question. Are you suggesting that your POCO is setting up their single-phase customers with non-separately-derived-systems? Is there an electrical connection between the primary-winding to secondary-winding of their transformers?

would you like a photo? a bond across these two points are do not keep it from being a separately derived system, current only flows back to source, it does not flow across this bond in normal use, and yes this is the way it is done in many areas with a Y system, I will take a photo so you can see and post it tomorrow

 

[suemarkp]

I am not sure where you are going with this, so maybe you can clarify it some more. It kind of sounds as though you think I am suggesting the Earthen-ground is supposed to do something about fault current. That is not what I said.

What I'm saying is not correct is this: "When metallic piping enters the Earth, it is grounded and held to ground potential." How the voltage gets on the pipe can be multiple ways (fault, normal voltage drop on neutral, elevated voltage on neutral from a failing/loose neutral). The why doesn't matter, as there is almost always some voltage on the neutral compared to the earth.

As other have mentioned, the resistance of the earth is too high to pull the voltage on that pipe to zero in less than a few feet of soil. Length doesn't matter much, as it is the small surface area of the dirt touching the electrode that is the problem. Once you've got the volume of a few feet of dirt, there is much more soil-soil contact and the voltage is quickly becomes "near ground potential".

"Ground potential" is difficult to define, as it can vary depending on where you poke a hole in the earth to measure as a reference. That is why "step potential" is such a major problem.

 

[Rick Christopherson]

would you like a photo? a bond across these two points are do not keep it from being a separately derived system, current only flows back to source, it does not flow across this bond in normal use, and yes this is the way it is done in many areas with a Y system, I will take a photo so you can see and post it tomorrow

A photo is not going to explain where the connection electrically resides. Just explain it in non-jargon terms where this connection is made between the primary-winding and the secondary-winding. By the way, it is not about current-flow. It is about voltage.

 

[Rick Christopherson]

As other have mentioned, the resistance of the earth is too high to pull the voltage on that pipe to zero in less than a few feet of soil.

Your statement is the same mistake I already pointed out to someone else. It doesn't matter how much resistance is across a path, if no current is flowing through that path, then both ends of the path must be at the same voltage. That is Ohm's Law.

The resistance of the connection is not stopping it from pulling the voltage down. There may be a voltage drop due to current sinking through the ground rod, but that is not the same as your statement above.

 

[Smart $]

A photo is not going to explain where the connection electrically resides. ...

Then perhaps a diagram...

If the left pot were removed, you'd have a typical single phase service.

 

[Rick Christopherson]

Then perhaps a diagram...



If the left pot were removed, you'd have a typical single phase service.

I don't see an internal bond inside the can that was otherwise suggested. I see an electrician that made an improper external connection that will kill someone when a tree drops on the neutral conductor upstream from the can.


Break the neutral upstream from that can:
C-phase = H1 = H2 = N = n = G = dead person

While we're at it, since G=C-phase:
G = n = x2 = x1 = x3 = c = a = totally dead person there too

 

[Smart $]

I don't see an internal bond inside the can that was otherwise suggested.

Don't know what was suggested. You guys get so verbose, I just skim the posts.

I see an electrician that made an improper external connection that will kill someone when a tree drops on the neutral conductor upstream from the can.


Break the neutral upstream from that can:
C-phase = H1 = H2 = N = n = G = dead person

While we're at it, since G=C-phase:
G = n = x2 = x1 = x3 = c = a = totally dead person there too

Yes, that's one possibilty. However, other possibilities exist...

For what's depicted in the diagram, if (or when) the upstream neutral (N) breaks, the primaries act in series and single phase. Say it's a 4160Y/2400 primary. Each primary winding normally sees 2400. With an open upstream neutral, each primary would see [perhaps] 2080V 1?, dependent on balance of downstream loads (if any) and how much primary [broken] neutral current returns through earth and other paths around the break.

The difference between the above (what's depicted in diagram) and one-pot single phase service is that one or more other single phase pots may be located downstream and connected to the other lines, which would potentially provide the balancing just mentioned above. Some single phase service customers may not even notice anything.

I recall a thread quite some time ago talking about this very circumstance. Broken POCO neutral and current was traveling through neighborhood earth and people were getting shocked around their pool.

 

[Rick Christopherson]

Don't know what was suggested. You guys get so verbose, I just skim the posts.

Then you shouldn't be participating in a technical discussion when you admit you are not up to speed on it. :rant: It's not like you are new around here or something, and didn't realize that arguing with me was supposed to be some sort of cake-walk.

 

[Smart $]

Then you shouldn't be participating in a technical discussion when you admit you are not up to speed on it. :rant:

Skimming your posts exceeds your speed from my perspective.

It's not like you are new around here or something, and didn't realize that arguing with me was [NOT] supposed to be some sort of cake-walk.

:slaphead:

 

[iwire]

We have had past discussions about "super nodes" through the shared plumbing system before. However, during the course of those discussions it was revealed that too many situations were attributed to this fairly rare problem. It is far more rare (problem wise) than it was being given credit for.

I am not sure what you are trying to say but a metal water piping system that is common to more than one service is not rare at all in this area.

All I was pointing out was that often a metal water line has more than just it's contact with dirt as a path back to the source. It often has multiple wire connections back to earth. (Edit: that should have been 'source' not 'earth')

 

[Rick Christopherson]

I am not sure what you are trying to say but a metal water piping system that is common to more than one service is not rare at all in this area.

All I was pointing out was that often a metal water line has more than just it's contact with dirt as a path back to the source. It often has multiple wire connections back to earth.

I'm sorry for the confusion. I did not mean to imply that the common plumbing was rare. It is only the alleged problems that were rare, or more specifically, overstated.

That was 2 years ago, so forgive me for not recalling the specific final conclusions of the discussion. Nevertheless, they did address the myths.

 

[don_resqcapt19]

No they are not, and you need to read up on what constitutes a seperately derived system. Bonding primary neutral (or center-tap) to secondary neutral automatically constitutes a non-seperately-derived-system.

If this is a response to my comment that all transformers installed in a code compliant manner have a electrical connection between the primary grounded conductor and the secondary grounded conductor, then you need to understand the code rules that apply to the installation of transformers. The code is very clear that the transformer is SDS unless there is a direct connection of a circuit conductor from one system to a circuit conductor of another system.

The code requires that the primary feeder to the transformer have an EGC and that conductor be connected to the non-current carrying parts of the transformer. The code requires that the secondary have a supply side bonding jumper that will be connected to the non-current carrying parts of the transformer. Assuming that both systems are grounded systems then there is a direct code required electrical connection between the grounded conductor of the primary and the grounded conductor of the secondary.

 

[don_resqcapt19]

I'm sorry for the confusion. I did not mean to imply that the common plumbing was rare. It is only the alleged problems that were rare, or more specifically, overstated. ...

The problems caused by the parallel path for the grounded conductor current via the water pipe may be overstated, because the "problems" are only noticed when there is a problem with both the service grounded conductor and the water pipe. In a typical installation in an area with a common metal underground water piping system, it is not uncommon to find 20% or more of the grounded conductor current flowing on the water piping system. This poses no problem to the people working on the water piping system as long as there is no problem with the service grounded conductor. The only voltage that will appear between the two ends of the water pipe when it is cut is the voltage drop on the service grounded conductor between the secondary of the transformer and main bonding jumper at the service disconnect. If the service neutral is open, then there is a serious hazard to the person who cuts the water pipe and gets between the two ends. This happens often enough that some water companies require that their workers bond across the water pipe so that there is still an electrical connection between the two ends of the pipe when they cut it.

 

[iwire]

This happens often enough that some water companies require that their workers bond across the water pipe so that there is still an electrical connection between the two ends of the pipe when they cut it.

And some water departments are installing dielectric fittings at the homes water service entrance. I think Tom Bakers area was doing that.

 

[iwire]

I'm sorry for the confusion. I did not mean to imply that the common plumbing was rare. It is only the alleged problems that were rare, or more specifically, overstated.

That was 2 years ago, so forgive me for not recalling the specific final conclusions of the discussion. Nevertheless, they did address the myths.

Thanks, for the clarification.

 

[Strathead]

8 pages of stuff! There are two major issues regarding a water pipe correct? One is utilization as a grounding electrode per 250.52. The other is 250.104. It seems to me that the O's question was in regards to 250.52, how often does anyone here see a new installation where the incoming water system is metal underground water piping? Even on the high end specification jobs nowadays, I usually see plastic. I have read that the Concrete encased electrode is a very effective connection to earth ground and that is why the code is no requiring it in all new contruction. Why not modify the code, to require the UFER as the primary grounding source for all new contruction? Removing it as a method period from 250.52, unless one can proove that an underground water pipe is at least 10 feet in length, which means digging it up in existing construction? Otherwise, how deos anyone know that it is a proper electrode?

On top of that, why does the bond for 250.104 need to be a table 250.66 sized conductor? What makes the water piping inside the structure any different that other metal systems? On a side note, how does one go about bonding the parts of the water piping system together? It seems to me that the code doesn't designate what constitutes a part of the system, so any 2 foot section that is spearated by a dielectric fitting, for example would need to be bonded over the fitting with a 250.66 sized bonding jumper. Especially including a bond between the cold and hot water at ANY heater including and insta hot. Why isn' this done?

 

[jxofaltrds]

8 pages of stuff! There are two major issues regarding a water pipe correct? One is utilization as a grounding electrode per 250.52. The other is 250.104. It seems to me that the O's question was in regards to 250.52, how often does anyone here see a new installation where the incoming water system is metal underground water piping? Even on the high end specification jobs nowadays, I usually see plastic. I have read that the Concrete encased electrode is a very effective connection to earth ground and that is why the code is no requiring it in all new contruction. Why not modify the code, to require the UFER as the primary grounding source for all new contruction? Removing it as a method period from 250.52, unless one can proove that an underground water pipe is at least 10 feet in length, which means digging it up in existing construction? Otherwise, how deos anyone know that it is a proper electrode?

On top of that, why does the bond for 250.104 need to be a table 250.66 sized conductor? What makes the water piping inside the structure any different that other metal systems? On a side note, how does one go about bonding the parts of the water piping system together? It seems to me that the code doesn't designate what constitutes a part of the system, so any 2 foot section that is spearated by a dielectric fitting, for example would need to be bonded over the fitting with a 250.66 sized bonding jumper. Especially including a bond between the cold and hot water at ANY heater including and insta hot. Why isn' this done?

Marysville Ohio uses copper supply.

I agree with the hot/cold bond but everyone thinks I'm nuts on that one! Even when I explain that my reasoning comes from being Licensed as a Plumber and former Plumbing Inspector.

 

[iwire]

I agree with the hot/cold bond but everyone thinks I'm nuts on that one!

Why would it required to be bonded a second time if they are not isolated?

 

[kwired]

8 pages of stuff! There are two major issues regarding a water pipe correct? One is utilization as a grounding electrode per 250.52. The other is 250.104. It seems to me that the O's question was in regards to 250.52, how often does anyone here see a new installation where the incoming water system is metal underground water piping? Even on the high end specification jobs nowadays, I usually see plastic. I have read that the Concrete encased electrode is a very effective connection to earth ground and that is why the code is no requiring it in all new contruction. Why not modify the code, to require the UFER as the primary grounding source for all new contruction? Removing it as a method period from 250.52, unless one can proove that an underground water pipe is at least 10 feet in length, which means digging it up in existing construction? Otherwise, how deos anyone know that it is a proper electrode?

On top of that, why does the bond for 250.104 need to be a table 250.66 sized conductor? What makes the water piping inside the structure any different that other metal systems? On a side note, how does one go about bonding the parts of the water piping system together? It seems to me that the code doesn't designate what constitutes a part of the system, so any 2 foot section that is spearated by a dielectric fitting, for example would need to be bonded over the fitting with a 250.66 sized bonding jumper. Especially including a bond between the cold and hot water at ANY heater including and insta hot. Why isn' this done?

The concrete encased electrode has been in the code for a long time. It was not being used because of how it was worded. It used to say "if available". When they changed it (2005 I believe, maybe 2002) the wording was changed to "if present". That means if a qualifying electrode is present you must use it, not that you have to install a qualifying CEE. Previous to the change nobody was using the CEE because the footings were done and no longer accesible (making the "if available" wording kick in) when the electricians showed up at the project.

A water pipe electrode likely has lower resistance than CEE and is reason why it still is the "primary" electrode if it is present.

I agree with the comments on interior piping.