effectively grounded steel

[augie47]

I was discussing "effectively grounded building steel" with another inspector and recall some graphics providing assistance in determining "effectively grounded building steel" being a "grounding electrode" vs shell building steel. Does anyone have any graphics or info to help show the difference ?

 

[Rockyd]

Like this?

More can be found here.

 

[augie47]

that helped, and additional searchs at the site also reminded me of 250.52A2 thanks

 

[M. D.]

Does this help,..I know it is not a graphic but I thought you might like the link
http://ecmweb.com/mag/electric_beyond_nec_changes/

Grounding electrodes (250.52). Revisions to 250.52(A)(2) now clearly identify four ways in which you can use the metal frame of a building or structure as a grounding electrode:

1. 10 feet or more of a single structural metal member is in direct contact with the earth or encased in concrete that is in direct contact with the earth.
2. The structural metal frame is bonded to one or more of the grounding electrodes as defined in 250.52(A)(1), (A)(3), or (A)(4).
3. The structural metal frame is bonded to one or more of the grounding electrodes as defined in 250.52(A)(5) or (A)(6) that comply with the requirements of 250.56.
4. Other approved means of establishing a connection to earth.

The intent of this additional wording to the Code is to outline some acceptable requirements for use of structural metal members as grounding electrodes ? and to ensure their use as part of the grounding electrode system by properly bonding the structural metal members to other electrodes.

 

[tom baker]

We had good language in the 05 NEC for this, 08 changes a bit and does not allow to connect to metal water pipe to count as effectively grounded. The quote above is from the 2005 NEC.

 

[Rockyd]

Glad that worked for you Augie47. Amazing how this forum saves us (at least it saves me) in the field now and again

 

[LarryFine]

I was discussing "effectively grounded building steel" with another inspector and recall some graphics providing assistance in determining "effectively grounded building steel" being a "grounding electrode" vs shell building steel.

My first thought is that building steel is effectively grounded if it is attached to anchor bolts in direct contact with the foundation steel.

I wonder if being bonded to the service neutral qualifies. Is your thought in using the steel as an electrode, or in properly bonding it?

 

[augie47]

The way I've been taught, there's somewhat of a fine line there, and revisons to '08 have muddied the picture for me. Ptrior to '08, my thoughts were if the steel is "effectively grounded" then it is a grounding electrode. As such, it had to be connected to the system and you could also "jump" from it to another electrode, say the water line.
If it were not "effectively gorunded" steel, then it had to be "bonded" per 250.104.
'08 has added a paragraph (3) that seems to indicate connecting the building steel to another electrode not only bonds it BUT makes it an electrode. It sems to me, if you "jump" from steel that has been bonded but is not within itself effectively grounded, then you are using the steel as a condcutor.

 

[dana1028]

Graphic - Bldg Steel Effectively Grounded

Graphic - Bldg Steel Effectively Grounded

I was discussing "effectively grounded building steel" with another inspector and recall some graphics providing assistance in determining "effectively grounded building steel" being a "grounding electrode" vs shell building steel. Does anyone have any graphics or info to help show the difference ?

IAEI 2005 Analysys of Changes Power Point has a great graphic of the code section showing the building steel in contact with earth. I'm in the field and don't have that graphic with me, but if you email me I'll send that graphic to you.