3/0 GEC Installation

[Seven-Delta-FortyOne]

Commercial metal building.

Plans have a 3/0 GEC.
Apparently, an “Engineered Ground System”.

We have 10 mil vapor barrier, so while I’ll connect to a Ufer, in my opinion, I need two ground rods outside. Plans only show one however.

I have a few ideas about the logistics of this installation.

I could run the wire continuous through the ground clamps, and attach it to the out side of the building.

I’d prefer to run it in conduit, with that conduit to ground clamp fitting that I can’t remember the name of right now.

But the physics of fitting two of those, plus a feed through 3/0 on one ground rod is something.

I could mount a J-Box with a ground bar, and run 3 individual 3/0 to each rod plus the Ufer.

I ready don’t want to have 3-3/0 coming into the panel landing on the ground bar.


What are some ways you guys have done this?

 

[letgomywago]

2 clamps on first rod to second.
Look into crimps this size of project could make it worth while
Maybe RFI the GEC for groundrod and ufer

 

[Seven-Delta-FortyOne]

I have all the crimp tools.

Ill have to look for tee crimp connectors in 3/0.

 

[Barney B]

Did your AHJ approve plans with a CEGE above a vapor barrier?

 

[letgomywago]

I have all the crimp tools.

Ill have to look for tee crimp connectors

Permaground Copper Grounding C Crimp, Main Conductor Range 4/0-3/0 Sol, Tap Range 4/0-3/0
Listed for grounding

 

[infinity]

Apparently, an “Engineered Ground System”.

Apparently not very good engineering with a vapor barrier below the footing and a #3/0 to a single ground rod. All that is required by the NEC is a #6 to two ground rods. If you want to follow their design I would install a ground bus and run a single #3/0 to the service disconnect.

 

[Seven-Delta-FortyOne]

These is the most, uh, Spartan set of plans I’ve ever worked off of, especially for commercial.

The vapor barrier isn’t even shown, but it’s required here.

It does show the CEE, plus one ground rod. Stamped by the AHJ.

I called the engineer who did the structural s and the plans, and he said he just copied what was given him by and electrical engineer that did the ground system years ago when the parcel was first developed. Apparently the AHJ required that.

It’s a multi-phase commercial development.

After how long it took to get the plans approved and a lot of headaches, I opted not to try to get that changed, even though it’s goofy to me, and just put in what they have.

I like the ground bus in a separate box. I think that would be the cleanest.

 

[Seven-Delta-FortyOne]

So after a closer reading of 250.64(c), it doesn’t appear that a busbar in a J-box is permitted.

 

[curt swartz]

Is the electrical engineer activly involved with the project? If so talk to them about the grounding. If the engineer is not involved talk to the electrcial inspector. If most cases they are looking for NEC minimums and not concerned about following every detail of the plans.

 

[Seven-Delta-FortyOne]

Footing inspection is tomorrow and I’m going to bring it up, but I’m sure he’s going to want to see installed what is in the plans.

Dont know who the EE was, it was done years ago during first phase of development.

As an aside, in my opinion, if the rebar does not qualify as a CEE, then it’s not required to be bonded. Its not a “normally non-current carrying metal part, likely to become energized”. In my opinion.

Another option I thought of, this is a metal building, and steel columns are permitted to be used to extend a GEC.

I could land all three on the column, and then bond the column to the bar in the panel. I’ll bring that one up tomorrow as well.