Dwelling Unit Grounding Debate

[NTesla76]

2023 NEC
Single family home has an emergency service disconnect outside (meter/main).
Bonding screw is installed in emergency service disconnect
4 wire from emergency service disconnect to interior panel.
Interior panel has equipment ground bar installed. Neutrals and grounds separated.
Grounding electrode conductors to concrete encased electrode and copper water line terminate in interior panel.
I say 250.24 does not allow this.
Another inspector says 250.118(B) Exception allows this.

Any input?

 

[infinity]

The GEC must terminate in the service disconnect on the outside. You could set up the EM disconnect as not service equipment with 3-wire to the service disconnect in the panel but that's not what you've described.

 

[NTesla76]

After reading 250.118(B)(1) Exception several times, I'm not exactly sure how this would apply.

 

[tortuga]

After reading 250.118(B)(1) Exception several times, I'm not exactly sure how this would apply.

The Exception states:

A wire-type equipment grounding conductor installed in compliance with 250.6(A) and the applicable requirements for both the equipment grounding conductor and the grounding electrode conductor in Parts II, III, and VI of this article shall be permitted to serve as both an equipment grounding conductor and a grounding electrode conductor.

The way I read that is the equipment grounding conductor in the 4-wire feeder can also serve as a grounding electrode conductor if it meets all the requirements for both conductors.

Say for example you have a single family dwelling (SFD) that has a meter outside, run of conduit to a interior service panel. Your scope of work is to remove the meter and install a new combination meter/loadcenter so a new heatpump can be added on the exterior, you'll convert the interior service to a feeder, update the grounding electrode system (GES) and seperate grounds and neutrals in existing panel.

Since there is a existing 1-1/4" EMT to the interior panel you pull new #2 CU's and per T250.122 you size your EGC as #6.
The #6 green is actually larger than #8 the minimum size required for a GEC in 250.66 based on the #2 CU.
You can add bond wedge on each end of the raceway, and install this #6 per 250.64(C) and per the exception it can serve as both a EGC / GEC.
In the existing panel all the other GEC's move to a new ground bar.

 

[augie47]

I would agree that 250.118(B)exception would allow the installation but meeting the bonding requirements might be more trouble than terminating directly to the emergency disconnect.

 

[tortuga]

I would agree that 250.118(B)exception would allow the installation but meeting the bonding requirements might be more trouble than terminating directly to the emergency disconnect.

Yeah I have never done it that way that I can recall, I think the exception is newer,
I tried to think of a example of when I would do it, I was thinking in my example not a EM disconnect rather it would be a meter/main/loadcenter, and a manageable wire size like #6 green.
Even then both the concrete encased electrode and water clamps would need to be very close to the existing interior panel, and / or you alredy own a crimping tool.