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#14351 09/19/02 06:15 PM
Joined: Jul 2001
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Who determines if a structual metal member in an existing building is "effectively grounded"? (NEC 250.52(A)(2)
Is there a particular test performed to decide?

#14352 09/19/02 06:46 PM
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Frank:
I guess it depends on who is asking, or requesting the bonding info.
The electrical contractor has the NEC responsibility in new construction, and major renovation work here. THe iron workers make-up "tight" connections, and we bond to the main beams usually. If the client, architect, engineer, etc. specs or requests, we install jumpers as specified.

John


John
#14353 09/20/02 06:22 AM
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HotLine1-

Typically, where are the jumpers normally installed?

#14354 09/20/02 07:12 AM
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Frank,
You can get IAEI Soares book on grounding for a very thorough explanation. If the steel is attached to bolts, in concrete, underground, it is basically considered grounded. It can get more complicated and I suggest a good read of Soares.

All steel needs to be bonded to the neutral though, don't forget that.

jumpers do not need to be attached for continuity, only welded or bolted together, and that usually is accomplished by the steel guys.

#14355 09/20/02 07:23 AM
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Thank you for responses. I'm meeting with an Electrical Engineer at job site this morning. Briefly, a separtely derived system is going to be installed on the eighth floor of our City Hall Building for County wide Court system. It is going to provide power for a computer room.
Running a grounding electrode conductor to the water meter in the basement is one option. Of course a ground rod must be driven. The other option is to use the structural building steel which does not require a driven ground rod.

Frank

#14356 09/20/02 08:37 AM
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Frank,

250.30(A)(4) specifies that it shall be the nearest of the two (eff. grounded structural steel or water pipe) that is used.

The way I read it a rod is not required either way if the steel or water pipe is available/used per 250.30(A)(4)(3)

Bill

[This message has been edited by Bill Addiss (edited 09-20-2002).]


Bill
#14357 09/20/02 02:55 PM
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Bill-

The Electrical Engineer deemed the structural metal not effecively grounded. He wants to use the metal water pipe. Wouldn't 250.53(D)(2) apply. ie. Supplemental electrode required, or doesn't that apply for separately derived systems?

Frank

#14358 09/20/02 03:33 PM
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Frank,

I read it that the rod is not required in this case (per 250.30(A)(4)(3)
) if you use the steel or the water pipe within 5 ft of point of entrance ro the Building. Does anyone else agree?

Bill


Bill
#14359 09/20/02 04:03 PM
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dis

#14360 09/21/02 07:54 AM
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Bill-

I have to continue to research this. I guess the basic question is: When using a metal water pipe for a grounding electrode for all Code applications, is a supplemental electrode required?

Frank

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