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PostPosted: Fri Sep 24, 2004 5:42 am 
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Joined: Mon Aug 09, 2004 11:28 pm
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Location: spokane, wa
OK, Ive reviewed the star grounding system that will help eleminate the potential for a ground loop, but this one may be a little different. Let me throw another one by some of you.

I have the possibility to do a little wiring for a client that has a steel building, steel studs, and metal outlet boxes mounted to the steel studs. No isolated ground. Pretty much EVERYTHING is bonded together, metal boxes to metal studs, metal studs to metal building, and the building is bonded to the service via copper conductor and bolted lug. The whole install is one big metal structure bonded and grounded together.

Does this scenario create a better chance of ground loop problems, or not. I am not looking for a perfect answer, just wondering if this has been covered and/ or if anyone has any interesting input.

I have the opportunity to wire a home theatre and some small XLR wiring for the guitar player who lives there. (They have turned a big shop into a residence/ crash pad)

thanx

d

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PostPosted: Fri Sep 24, 2004 6:25 am 
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Location: Music City
I'm not for certain, but from reading another post that Steve had made several months ago, I seem to remember, the metal boxes should have their separate ground from the isolated outlets.

In other words, it's probably fine for all the boxes, etc to be grounded, but I would still recommend or suggest running isolated/star grounding for the outlets, so all outlets have one common ground point.


If that makes any since? :? That's my take on it anyway.


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PostPosted: Fri Sep 24, 2004 10:51 am 
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Location: spokane, wa
The problem is that it is all existing, and sheetrocked. I just wanted to go into the job (if I do it) with a better understanding of what may happen if we do a little audio install using the existing plugs and stuff.

Ive put in a few theatres using existing wiring and there were no problems, but this whole building is metal, studs are metal, etc...

d

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PostPosted: Fri Sep 24, 2004 2:37 pm 
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From your description am I right in thinking there is no conduit involved, but instead romex with stud shields? If that's the case, there's no way to add IGR's correctly. If, however, I missed something and the wiring is individual conductors in conduit, you could always use one of the wires to pull two more, and add separate grounds.

If that's not possible, the best you could probably do is to use only one outlet for all electronic gear, and if possible isolate each chassis from the others, so that each get their ground from the same ground pin at the wall receptacle.

Then, for optimum S/N, custom cables can be made for each connection, with the shield only connected at one end (like the receiver in this case) - this takes shielded twisted pair for unbalanced audio; you use the red for center conductor, the black and shield go to ground at the receiver, and the shield is clipped just short of making connection with the plug at the other end, while the black is connected to the outer conductor at the far end of the cable.

That's about the best you can get if you can't add wires and the job's already closed up... Steve


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