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#216200 - 11/01/15 03:43 PM GEC dilemma
sparkyinak Offline
Member

Registered: 07/08/07
Posts: 1286
Loc: Alaska
Here is my dilemma. I have to ground a weather vane which is a 20 feet of 2" rigid in the center and above the main roof. It is anchored to the wall where the roof access three stories up. The building is part poured concrete and prefab concrete located in a very hospitable area weather rise. Imagine a harden concrete bunker that is a maze of floors, rooms, and concrete. This building is like that but worse.

The #2 GEC needs to go down two floors and a good 100' through a dozen concrete walls which will not be easy to drill, even for concrete. I could take it down to the basement then across to bypass a few walls, however being a GEC, the shorter the better. Running it on the exterior is out and due to the prefab concrete, I can't count on using the building steel. The old drawings are ambiguous and without reliable information, I can't use building steel.

One option I would like to explore but not exactly to code is panel feeders are all rigid pipe which are encased in the pour concrete. Before go and seek an engineers and AHJ's approval, my theory is bonding to the rigid feeder a near by panel. This would be the shortest route back to the MDP (providing proper bonding).Would this present a potential problem besides code would this not be no way possible to keep from even trying getting approval?

It's out of the box approach and the code is the box. I'm just trying to avoid a laborious process when there is in its self a very long run for a GEC. ensuring that it a safe and reliable installation. I'm not out anything on this project but time. It's the customer, ie the tax payer that will be footing the bill and I'm about safety and economics of any project

Is this idea dead before it started?
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#216201 - 11/01/15 04:18 PM Re: GEC dilemma [Re: sparkyinak]
HotLine1 Offline

Member

Registered: 04/03/02
Posts: 6785
Loc: Brick, NJ USA
First....is what you are attempting 'lightning protection'??

If so, that is out of the NEC realm, and is done to UL specs AFAIK. Braided Cu conductors, run on the exterior, on standoff supports, eliminate any 'tight bends', and terminate at a ground rod. Then bond all rods AFAIK.
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#216202 - 11/01/15 07:04 PM Re: GEC dilemma [Re: HotLine1]
sparkyinak Offline
Member

Registered: 07/08/07
Posts: 1286
Loc: Alaska
It's more grounding and static build up. Lightening is a rarity here and then it's the higher elevations. Weather vane has a wind meter which is wired into a very expensive data collecter with inline surge supressors so everything ahead of the supressors needs to be grounded straight to ground
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#216203 - 11/01/15 10:48 PM Re: GEC dilemma [Re: sparkyinak]
gfretwell Offline

Member

Registered: 07/20/04
Posts: 9012
Loc: Estero,Fl,usa
You definitely want your grounding conductor shorter than your data cable, if you have to coil the data cable up.
(actually not a bad idea, along with ferrite beads)
You want the lightning shot bonded out before it can get to the equipment. I am not sure how the science works out but that is what works practically.

If lightning is even a possibility you need to follow John's advice. You do not want that fire ball transiting the building. It will be flowing down the outside of that conductor.

I didn't use anything but a long data cable and some ferrites on my weather station and that mast has been hit at least twice with no damage.

Best is if you can optically or RF connect your data, even if the air gap is only an inch or so.
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