ECN Forum Forums Code Related Discussion NEC & other Code issues 250.66 and Ufer

250.66(B) says that the "portion of the conductor that is the sole connection to the grounding electrode shall not be required to be larger than #4 copper wire"

If I have a 400 amp service and my only grounding electrode is the Ufer, do I need to use #2 copper per the table (250.66)?

No, it "Shall not be required to be larger than #4 copper wire".
The paradox is, if you have metal water pipes in the house, that connection needs to be sized to 250.66, even if you think it might be plastic where it goes into the ground.

Thank You Greg. This is new construction with Pex, and no gas at all. So the Ufer is the only grounding electrode. Our local AHJ seems to think there must be at least one GEC in the system sized to table 250.66, so if there is only one grounding electrode they consider it the "main grounding electrode" and want the GEC sized to the table regardless of the grounding electrode type. They will only allow the #4 to the Ufer as a tap from another GEC sized to table 250.66.

What would that other electrode be?

Your AHJ is not wrong (according to 90-4) but he is certainly confused.

I guess it's easier for me: the EE calls out the GEC system conductors.

As a general principle most AHJ are not going to allow downsizing bonding connections in the GEC System.

So if you have a Ufer using # 2 then that self same #2 is expected to be brought up to the GEC bonding/grounding rail in the Service.

Strictly speaking, a Ufer is a concrete encased electrode. Yet, it is commonplace for 'Ground Ring' sized conductors to be encased in concrete, too. Strict construction of the terms would require Ground Rings to be set bare into the soil, underneath the pour. I never see that.

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Out my way, #4 Ufers are explicitly mandated for 200 A Services. No ifs, ands or buts.

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Since one is expected to have an UNBROKEN CONDUCTOR RUN from the GEC up into the Service any effort to complicate it by downsizing with an irreverseable ( Cadweld/ultra-compression connector ) connector are entirely uneconomic.

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All of which makes me wonder why such brain matter is focused upon shaving that last itsy-bitsy bit of copper out of a job.

To my mind, the very short runs involved with GEC Systems make them no place to concentrate ones energies.

Instead, focus on clean, quick installations. That's where one makes it or breaks it.

I’m not sure I’m following this. Is the inspector saying that a GEC sized per Table 250.66 is required to be run and connected to the #4 CU for the Ufer?
If so, I would think that since 250.66[A] clearly says that portion of the conductor that is the sole connection to the CEE/Ufer only needs to be sized at #4 CU, the #4 from the Ufer should be able to be run to the main service equipment and connected to the neutral bus as is without issue.
Don’t we basically do the same thing with #6 CU and ground rods?

I suspect the inspector is confused because there is no metal water pipe in there.

We are not trying to save copper. What happened was a #4 solid got used to attach to the re bar in the slab before the pour, we were not in the picture yet.

Now we come along with a 400 amp service and the inspector says we need either a #2 to the re bar and if not we need to drive 2 ground rods and attach a #2 to them.

BigB:
Depending on how much time you have on this job, you may just decide to drive the 2 rods & get on.

Or, take the 'good fight'! A conversation with the inspector, book in hand. Or, a conversation with the Chief Inspector, again book in hand.

Here in NJ, you could go further via the Board of Appeals; $150 filing fee, 30-90 days to get on the docket & if you are anything other then a sole proprietor, bring the lawyer.

IMHO, the conversation route is the best shot, & if not helpful...drive the rods.

It's not conceeding defeat, its making the best decission.

Your inspector is just further confirming his confusion about 250.66. At a certain point you should just do what he says and get on with your life. You might prevail in an appeal but I doubt you will win.