Building addition grounding

[steve66]

An existing building has a 480V, 400 A service with 600 KCM service entrance conductors.

The building will get a new addition, and the contractor will run a 300 amp feeder (350 KCM wire) to a new panel in the new addition.

I would like to specify a concrete encased electrode in the new addition. In addition, it the addition will have a new water service.

Question #1: Can the concrete encased electrode just be connected to the new building steel? Or do I have to run a 1/0 wire back to the existing service panel.

Question #2: What size wire do I need to run to the new water service, and for the meter jumper?

I guess I'm mostly confused because the service isn't near the new addition.

Thanks in advance:
Steve

 

[augie47]

The method I have used in the past, which hopefully others find Code compliant, was to assure the addition steel is connected structurally or via "jumper" to the existing steel and then connect my new electrodes (Cee, new water, etc) to the new steel based on the service size.

 

[roger]

I agree with Gus, all that would be needed is to bond everything together and follow the rules of 250.104.

IMO there is no need to for any bonding of the footer steel, the GES is already in place.

Roger

 

[George Stolz]

Question #1: Can the concrete encased electrode just be connected to the new building steel?

I agree with Roger and Gus.

Also, the new water service bonding jumper could simply connect to the building steel.

Question #2: What size wire do I need to run to the new water service, and for the meter jumper?

1/0 CU or 3/0 AL.

1/0 CU from building steel to water pipe.
#4 CU from CEE to building steel.
1/0 CU minimum from building steel to the service, but I assume it's already that big or bigger.

 

[Pierre C Belarge]

These additions are installed in so many different ways, but the end result in my opinion is either of two methods.

The steel for the structure being added is structurally tied into the existing building and no additional bonding is required.


The steel for the structure being added is not structurally tied into the existing building and bonding of the steel will be required.

Obviously, the feeder supplying the new panel will require an EGC as per 250.118.


There is a 3rd scenario I just thought of. The wall(s) & door(s) between the existing structure and the addition may be firewalls and doors. If that is the case, the addition would be considered a separate structure, and grounded as such, which means the concrete encased electrode would be part of the grounding electrode system.

 

[steve66]

The method I have used in the past, which hopefully others find Code compliant, was to assure the addition steel is connected structurally or via "jumper" to the existing steel and then connect my new electrodes (Cee, new water, etc) to the new steel based on the service size.

That's pretty much what I was thinking too, but I wasn't sure if that would comply.

IMO there is no need to for any bonding of the footer steel, the GES is already in place.

Roger

I thought about that too, but I could also see how 250.50 could be interperted such that a CCE would now be "present". Anyhow, I think CCE's really make for a good ground, & I usually try to include one whenever possible.

Steve

 

[George Stolz]

Just noticed:

An existing building has a 480V, 400 A service with 600 KCM service entrance conductors.

The building will get a new addition, and the contractor will run a 300 amp feeder (350 KCM wire) to a new panel in the new addition.

Was the existing service that underutilized?

 

[steve66]

1/0 CU or 3/0 AL.

OK, I thought I could reduce this to #6 copper per 250.66(A). But I see now that the "pipe electrode" in 250.66(A) is not the same as the water service pipe.

Just noticed:


Was the existing service that underutilized?

Yes, the existing service was once used for welders for welding classes. But all the welding equipment has been removed.

The thing I didn't mention is that this building also has a second existing service that is 208/120V, and it basically runs the entire existing building.

Since we aren't doing anything with the 208V service, I'm wasn't planning on messing with it's grounding. Like Roger said, I assume its already grounded per code.

Steve