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#184066 01/31/09 08:42 PM
Joined: Sep 2005
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Tripp Offline OP
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It seems that all too often I get called by someone who wants a ground for their computer where the house wiring has no ground. They've had the idea that I could just take a separate ground wire to the outside or to the panel.

I thought that was a code violation because it would be creating more than one path to ground, or something like that. The best that I could do, I would tell them, is to install a GFCI for personnel protection (per NEC 406.3(D)(3))and a surge suppressor for equipment protection.

But today I was reading an old article by Rex Caudwell in which he says that "neither a surge arrestor at the panel nor a point-of-use arrester at the appliance will work properly without a high quality grounding system to dissipate the surge."

So I decided to investigate further and found me 250.130(c), in which I was surprised shocked to learn that I can, indeed, run a separate EGC from an ungrounded recept right out to the GE or any point along the GE system.

So am I getting this right? confused And if so, how could I have missed this all these years? blush crazy

2017 / 2014 NEC & Related Books and Study Guides
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L
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--So I decided to investigate further and found me 250.130(c), in which I was surprised shocked to learn that I can, indeed, run a separate EGC from an ungrounded recept right out to the GE or any point along the GE system.

So am I getting this right? confused And if so, how could I have missed this all these years? blush crazy--

many miss this,not the preferred practice but compliant.
unless in Massachusetts. Not allowed here.

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Tripp Offline OP
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Wow. Well, I'll be darned.

BTW, would you tell me then, why this is not the "preferred practice"? Is it for the reason I stated? (or tried to state, in a rather bumbling fashion -- something about multiple paths to ground?)

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L
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Most like to keep all conductors for a ckt together.Or a new ckt for the device.

Electrically it's fine.

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Tripp Offline OP
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Thanks again.

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G
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The real problem is how you actually connect this. If you read 300.3(A) it says you can't just string THHN back to a ground point. (not a chapter 3 wiring method)
On the other hand I think if it is suitably protected that is better than having ungrounded outlets.
I have heard of running a new grounded circuit in the accessible areas and tapping off that with fished grounding conductors down/up to the ungrounded outlets through the wall where they are somewhat protected.
I would talk to the AHJ and see what they think.

Personally I would just run new cables for grounded outlets in the locations that actually use the ground. (most consumer products have 2 prong plugs anyway)


Greg Fretwell
Joined: Sep 2005
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Tripp Offline OP
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Okay, Greg. Lts more code to check out. And you're right: the AHJ is a very good idea.

As for "I have heard of running a new grounded circuit in the accessible area and tapping off that with fished grounding conductors...to the ungrounded outlets through the wall where they are somewhat protected" -- if I am able to fish a ground, usually I can fish the entire NM cable (as you suggest in your next paragraph).

"Most consumer products have 2 prong plugs anyway": I am looking at the adapter for this laptop rigth now and it is 3-prong! smile

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G
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As was pointed out, if your plug has a ground pin, the equipment expects a real ground. You are taking your chances with an adapter. I certainly would not connect an ungrounded PC to a grounded phone line. Your modem becomes the fault path.


Greg Fretwell
Joined: Aug 2007
Posts: 853
L
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Originally Posted by gfretwell
The real problem is how you actually connect this. If you read 300.3(A) it says you can't just string THHN back to a ground point. (not a chapter 3 wiring method)

I would talk to the AHJ and see what they think.

Personally I would just run new cables for grounded outlets in the locations that actually use the ground. (most consumer products have 2 prong plugs anyway)


300.3(2) says we can run the bond/ground alone. 300.4, protection must be considered as well.

That's what I meant by 'Preferred' method Tripp.
If you can snake in the ground,(chances are you need to gt all the way back to the panel anyway) A new ckt is just as easy/hard.

Joined: Jan 2005
Posts: 5,316
Cat Servant
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I'm sorry, but I was under the impression that stringing in a new ground was a practice no longer allowed. That is, all conductors had to be in the same cable / conduit.

I remeber this being depicted when grounds were introduced, and I have encountered houses built with a separate ground strung along with the 2-wire romex. Yet, I have heard many assertions that you can't do this any more ... nor can you just tie it to any handy piece of plumbing.

I do see the need for a real ground path, though. Electronic appliances often use the ground path ... either to always have power ("instant on," timers, motion sensors, etc.), or in order for the surge suppressor to work.

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