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#14351 - 09/19/02 03:15 PM Structural metal member
Frank Cinker Offline
Member
Registered: 07/29/01
Posts: 317
Loc: Pennsylvania
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?
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#14352 - 09/19/02 03:46 PM Re: Structural metal member
HotLine1 Offline


Member
Registered: 04/03/02
Posts: 6833
Loc: Brick, NJ USA
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
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John
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#14353 - 09/20/02 03:22 AM Re: Structural metal member
Frank Cinker Offline
Member
Registered: 07/29/01
Posts: 317
Loc: Pennsylvania
HotLine1-

Typically, where are the jumpers normally installed?
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#14354 - 09/20/02 04:12 AM Re: Structural metal member
George Corron Offline
Member
Registered: 05/16/01
Posts: 728
Loc: Lorton, Va USA
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.
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#14355 - 09/20/02 04:23 AM Re: Structural metal member
Frank Cinker Offline
Member
Registered: 07/29/01
Posts: 317
Loc: Pennsylvania
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
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#14356 - 09/20/02 05:37 AM Re: Structural metal member
Bill Addiss Offline
Member
Registered: 10/07/00
Posts: 4196
Loc: NY, USA
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).]
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#14357 - 09/20/02 11:55 AM Re: Structural metal member
Frank Cinker Offline
Member
Registered: 07/29/01
Posts: 317
Loc: Pennsylvania
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
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#14358 - 09/20/02 12:33 PM Re: Structural metal member
Bill Addiss Offline
Member
Registered: 10/07/00
Posts: 4196
Loc: NY, USA
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
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#14359 - 09/20/02 01:03 PM Re: Structural metal member
TE Offline
Member
Registered: 08/26/02
Posts: 37
Loc: USA
dis
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#14360 - 09/21/02 04:54 AM Re: Structural metal member
Frank Cinker Offline
Member
Registered: 07/29/01
Posts: 317
Loc: Pennsylvania
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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