CEE as a common for multiple services.

[Tulsa Electrician]

There is four services on a single building.
As part of the GES the four service all have a 3/0 GEC to the CEE.
The water service is plastic.
There is two rod electrodes driven at each service.
The metal part of the building has steel columns. (1 service)
The rest of the building is wood framed where the other services are located. (3 services)

From one service they have a GEC ran to building steel. The only tie to all four is the CEE.

Question:
Since the CEE is the only tie ( common) to the four and only one has a GEC to the steel. Would the CEE common be considered a violation under 250.53 (C) 2020 NEC.

 

[infinity]

Are there four separate services or four service disconnects?

 

[Tulsa Electrician]

Yes

 

[Tulsa Electrician]

Service one feeds the MDP for house equipment. Single service disc. (GEC to steel, 2 rods,cee)

Service two fees commercial area. Single service disc.
(Gec to cee,two rods)

Service three and four feed multifamily.
3 has two service disc, one location ( grouped)
4 has three service disc, one location.(Grouped)
(GEC to cee, two rods)

3/0 to CEE and building steel
#6 GEC to rods.

 

[petersonra]

This sounds more like you have one service with multiple sets of service conductors.

The code would normally prohibit multiple services to a single building and most utilities won't do it absent some highly unusual situation like one service would not be able to be made big enough.

 

[winnie]

Is this officially 1 building or 4 buildings?

Are you saying that some of the services are supposed to be tied to building steel, but they are only connected via the CEE?

-Jonathan

 

[Tulsa Electrician]

I checked and it is a single bld.

Is this officially 1 building or 4 buildings?

Are you saying that some of the services are supposed to be tied to building steel, but they are only connected via the CEE?

-Jonathan

There is three separate transformers.

Maybe a quick drawing will help. I may be looking at this wrong.

This sounds more like you have one service with multiple sets of service conductors.

The code would normally prohibit multiple services to a single building and most utilities won't do it absent some highly unusual situation like one service would not be able to be made big enough.

 

[Tulsa Electrician]

see if this helps.

Not sure how they can say single building since its mixed use. Commercial and multifamily. That is what the AHJ determined.

 

[Tulsa Electrician]

I checked and it is a single bld.

There is three separate transformers.

I meant to say four, sorry

 

[Tulsa Electrician]

Are you saying that some of the services are supposed to be tied to building steel, but they are only connected via the CEE?

-Jonathan

Yes. One one service disconnect has a GEC to the building steel. This one is the MDP.

 

[winnie]

I'm not sure that it is a real safety issue (grounding has lots of crazy excess requirements), but I believe you have identified a potential code violation.

Each service is supposed to be connected to all available electrodes. I wouldn't stress about the connection from one service to the others' ground rods, but the connection to building steel serves both grounding and bonding. 250.53 (C) states that _rebar_ can't be used as the conductor to interconnect the various grounding electrodes.

Since CEEs are usually rebar, you probably have a code violation. On the other hand if copper is entering the slab from each of the services, you might be fine. (You could have copper wire connected between the services acting as both the jumper between electrodes and the connection to the rebar.)

-Jonathan

 

[Tulsa Electrician]

I'm not sure that it is a real safety issue (grounding .

Since CEEs are usually rebar, you probably have a code violation. On the other hand if copper is entering the slab from each of the services, you might be fine. (You could have copper wire connected between the services acting as both the jumper between electrodes and the connection to the rebar.)

-Jonathan

Good point, I will ask for picture of what they did. I like the idea of the 20' CU 3/0 and attachment. This way it would comply.

Thank you for a better way to do it when there is more than one service.

 

[Strathead]

250.58 Common Grounding Electrode. Where an ac system is
connected to a grounding electrode in or at a building or structure, the same electrode shall be used to ground conductor enclosures and equipment in or on that building or structure. Where separate services, feeders, or branch circuits supply a building and are required to be connected to a grounding electrode(s), the same grounding electrode(s) shall be used. Two or more grounding electrodes that are bonded together shall be considered as a single grounding electrode system in this sense.

250.68(C)(3)(c) states: Rebar shall not be used as a conductor to interconnect the electrodes of grounding electrode systems.

So that pretty much says, not legal.

 

[Tulsa Electrician]

Thank you. Wanted to make sure I was not missing anything. This was a change from 2020.

 

[Strathead]

Thank you. Wanted to make sure I was not missing anything. This was a change from 2020.

I should have stated that, but that is the 2020 code I was citing.

 

[jaggedben]

See comment here:

Grounding electrode system

I understand why we ground for nearby lightning strikes and surges. The other main reason we ground is to establish zero potential to neutral and ground, to the Earth. Is there more nuance to the purpose of establishing zero potential?

forums.mikeholt.com

If all services are connected to the CEE, then all the electrodes may be effectively connected to each other so there's no violation. But the details are a bit unclear.

 

[Strathead]

See comment here:

Grounding electrode system

I understand why we ground for nearby lightning strikes and surges. The other main reason we ground is to establish zero potential to neutral and ground, to the Earth. Is there more nuance to the purpose of establishing zero potential?

forums.mikeholt.com

If all services are connected to the CEE, then all the electrodes may be effectively connected to each other so there's no violation. But the details are a bit unclear.

There would still be a violation, because a CEE is not one of the code accepted means of connecting electrodes together.

 

[winnie]

Just a pedantic detail: a code accepted means of connecting electrodes together may also be a CEE. A suitably sized copper wire can be used to connect electrodes. If that wire is long enough and embedded in concrete that is in contact with earth, then it would also be a CEE.

That was the essence of my answer to the OP, that rebar is not an acceptable jumper, most CEEs are made of rebar, so most CEEs are not code compliant for interconnecting other electrodes. But an acceptable copper jumper could be part of the CEE, and that this might be a good solution in some situations.

Jonathan

 

[Strathead]

Just a pedantic detail: a code accepted means of connecting electrodes together may also be a CEE. A suitably sized copper wire can be used to connect electrodes. If that wire is long enough and embedded in concrete that is in contact with earth, then it would also be a CEE.

That was the essence of my answer to the OP, that rebar is not an acceptable jumper, most CEEs are made of rebar, so most CEEs are not code compliant for interconnecting other electrodes. But an acceptable copper jumper could be part of the CEE, and that this might be a good solution in some situations.

Jonathan

Good point. I was going to tell you you were wrong, then I read what I had written and realized I was the one mistaken. Oh Well!

As typical, we view things through a lens, which is why I always pull out a code book when answering a question instead of answering what I "KNOW". In his diagram, the chances of a copper UFER being run around those building corners is close to zero.

 

[winnie]

As typical, we view things through a lens, which is why I always pull out a code book when answering a question instead of answering what I "KNOW". In his diagram, the chances of a copper UFER being run around those building corners is close to zero.

Agreed. Unless someone specifically thought of this issue ahead of time, they probably just tied each service to a local bit of rebar and called it good.