GEC Routing in Building Steel

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jeremyp

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I'm a licensed electrician that works for a company that builds power houses, gear houses, pump houses, power centers, etc. We put copper halos around the buildings off of insulators for the GEC to bond all of the service equipment (meaning transformers of differing voltages and panels which have a neutral only bonded within its parent transformer). On the corners of the building we put copper plates for the field installation of the GEC to earth. We currently take bare copper wire from the grounding halo thru the side of the building and bolt to these copper plates. The buildings are completely welded steel, 1/8th inch skin, 1/4 inch floor, Steel I-Beam joists. All equipment is installed with machine threaded bolts.

After fighting with the siding guys, siliconing several sleeves I thought probably ought to have bonding bushings on them and arguing with a mechanical engineer later I am ready to ask for help from the forum. My thinking is: the entire building is welded structural steel, provided all bonding connections are made with machine thread bolts to welded copper plates then the halo around the building is unnecessary if not dangerous. I also fail to see the reason for running a wire thru the wall to a welded plate as the connection is already continuous.

Any help would be great, two or fifteen more outbursts from me might just get this pipe bender fired.
 
It's been said for a long time that possession in nine tenths of the law. When it comes to grounding/earthing perception is nine tenths of reality. Dirt worshipers are not rational beings.

There's nothing wrong with the halo. I see them all the time in shelters on cell sites. Not all shelters have them though, and if you want to have a good time get two engineers in the same room to tell you which is better, halo ground or single point. Nine hours of the work day will get eaten up and you get paid for it.
 
I feel like I might be missing something embarrassingly fundamental about this. We're throwing 200# of copper bus bar at steel, then 4/0 bare to another grounding plate welded to the same structural steel. I would understand if the whole thing was light gauge steel studs and FRP on an OSB floor, but I look at four welders everyday that are making my job significantly easier and a harem of mechanical engineers that I'm pretty sure don't understand the point.:thumbsup:
 
250.4 (A)(1) FPN An important consideration for limiting the imposed
voltage is the routing of bonding and grounding conductors
so that they are not any longer than necessary to complete
the connection without disturbing the permanent parts of
the installation and so that unnecessary bends and loops are
avoided.

I think the addition of a grounding bus hung on insulators lengthens the path. Bonding to structural steel provides the shortest path. I think anyways...:?
 
My thinking is that bonding structural steel does two things: Provided a pathway back to source neutral for any accidentally connected live parts and to provide a cage that has zero (or near to it) potential difference between normally non energized conductive parts. So, having a copper bus installed on insulators ring the building which are then cabled down to two welded plates on the corners of the building has created a situation where there is a potential between the steel floor a person is standing on and the copper bus. If there is a high voltage spike on the primary entering the building, which then induces or directly applies voltage to the case of the transformer (albeit bolted to the floor which is structural steel) is there not a possibility of a difference of potential between the copper bus and other steel components within the building? Would it not be preferable to have the potential of the entire building raised equally within itself during an over voltage by having the service equipment GEC bonded directly to the structure at each derived point instead of providing a pathway with lower resistance exposed on the interior carrying high voltage current?

I'm beating this dead horse because I think that at best the copper halo is unnecessary/redundant and at worst dangerous.
 
jeremyp said:
My thinking is that bonding structural steel does two things: Provided a pathway back to source neutral for any accidentally connected live parts and to provide a cage that has zero (or near to it) potential difference between normally non energized conductive parts. So, having a copper bus installed on insulators ring the building which are then cabled down to two welded plates on the corners of the building has created a situation where there is a potential between the steel floor a person is standing on and the copper bus. If there is a high voltage spike on the primary entering the building, which then induces or directly applies voltage to the case of the transformer (albeit bolted to the floor which is structural steel) is there not a possibility of a difference of potential between the copper bus and other steel components within the building? Would it not be preferable to have the potential of the entire building raised equally within itself during an over voltage by having the service equipment GEC bonded directly to the structure at each derived point instead of providing a pathway with lower resistance exposed on the interior carrying high voltage current?

I'm beating this dead horse because I think that at best the copper halo is unnecessary/redundant and at worst dangerous.
Click to expand...

I think the chances of such a situation happening are so rare that it just doesn't make any real difference.
 
jeremyp said:
...
I'm beating this dead horse because I think that at best the copper halo is unnecessary/redundant and at worst dangerous.
Click to expand...
That's always the case with anything electrically related.

IMO the halo is entirely unnecessary.
 
Smart $ said:
That's always the case with anything electrically related.

IMO the halo is entirely unnecessary.
Click to expand...

I believe it is possible to over think every situation, one find countless ways to improve most jobs, particularly if someone else did the job and two
to find problems that MIGHT result in the worse case scenario.
 
brian john said:
I believe it is possible to over think every situation, one find countless ways to improve most jobs, particularly if someone else did the job and two
to find problems that MIGHT result in the worse case scenario.
Click to expand...

I agree that it is easy to pick someone else's work apart, which is why I bite my tongue when looking at other electricians' work. I also agree that worst case scenarios are easy to come up with, but a bad design is a bad design and to keep on installing the same bad design is a waste. The halo itself isn't the only issue, running bare 4/0 out of the building thru a sleeve has it's own code and workmanship problems. To me, its like telling a guy to install fourth leg on a round table then lecturing him on the best way to adjust the fourth leg to prevent wobbling.
 
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