article 250.50

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mike k

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The drawings on the project I am working on show a ground ring around the entire building with multiple ground rods. Also has a 3 ground rod counterpoise, a connection to the water pipe and the building steel (at 1 location). The problem is the inspector is asking us to bond each steel column in the building to the ground ring. Is this required?
 
Re: article 250.50

Mike,
Good question. I can't see according to 250.52(A)(2) that you would have bond each beam to the ground ring. However if the AHJ says to, well you know the drill. A formal code interpretation will probably take about 3 months if you're lucky.

Britt
 
Re: article 250.50

Some questions that come to my mind is are the columns tied together or are they free standing with wood members? Are these columns tied to rebar encased in concrete?

Should these columns be tied to the rebar that is concrete encased or if they are tied with joist or purling then I don?t see the need for each to be tied to the grounding ring.

A column that is only anchored to concrete by some type of anchor bolt and has a wood rafter system is not effectively tied together. It cannot be used as part of the grounding electrode system and would be required to be bonded using table 250.122.
:)
 
Re: article 250.50

This is a steel bar joist structure.Therefore all the steel is tied to gether and effect bonded.
The columns are set on concrete pier pad which do have rebar in them and the floor pad also has rebar . We have bonded to the rebar in the pad,building steel (at one location) ground ring, water main and ground all rods.The real problem is this is a military base and the engineer is no longer under contract his contract was to provide only stamped drawings & specs.Therefore he will not take any RFI(s) in regards to any questions or clarifications. The inspector i referenced is an contracting officer employed by the military base. The contracting officer is not an engineer nor an electrician he only references the drawings and specs for compliance. The drawings do not call out to bond each column nor do the specs specifically. However they do ca;; for us to comply with NEC 250.50 whic now we have an interpretation issue.
 
Re: article 250.50

250.104 (C) Structural Metal. Exposed structural metal that is interconnected to form a metal building frame and is not intentionally grounded and is likely to become energized shall be bonded to the service equipment enclosure, the grounded conductor at the service, the grounding electrode conductor where of sufficient size, or the one or more grounding electrodes used. The bonding jumper(s) shall be sized in accordance with Table 250.66 and installed in accordance with 250.64(A), (B), and (E). The points of attachment of the bonding jumper(s) shall be accessible.
:)

Edited to add
Ooops, I see my mistake now, not 122 but 66
:eek:

[ June 24, 2005, 07:27 PM: Message edited by: jwelectric ]
 
Re: article 250.50

Mike I think you are forgetting a key part.

and is likely to become energized
Click to expand...
An isolated steel member is not likely to be energized. :)

[ June 24, 2005, 07:31 PM: Message edited by: iwire ]
 
Re: article 250.50

just what does "likely to become energized" mean?

it's a term not defined in the code.

generally, it seems to be understood that something is not likely to become energized if there is no source of electrical energy in the immediate vicinity.

I have seen it argued that having a piece of emt running up a column makes it "likely to become energized" because there is electrical energy near the column. In that case the individual who objected eventually decided that the beam clamps used to secure the emt to the column effectively bonded the column to the emt (a perfectly legal egc) so it was no longer an issue.

I also once heard that the beams holding up an electric crane are considered likely to become energized no matter what.
 
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