Multiple structural steel systems

[justin59]

I am working on a church that is half remodel and half new construction. In the new part of the sanctuary there are 5 steel structures that consist of 2 steel I beam posts and 1 I beam cross member. None of them are connected above grade but im pretty sure (but will verify monday) that they are connected by rebar in the footings. Also, there is one more structure just like the forementioned installed in the existing part of the building. I don't think that there is any connection to the other structures. My question is do I need to install a GEC between all of the structures if there is no connection between them or do I only need to run a GEC to one of them?

Thanks for any help.

 

[jca0108]

i would connect it as per 250.50. it says bond if present. also 250.52(A)(2)-2and 3 , 250.64(f) and 250.68(a) exception(2).its not the answer but its a start. almost forgot check 250.104(C) as well.

 

[kwired]

250.50 Grounding Electrode System.
All grounding electrodes as described in 250.52(A)(1) through (A)(7) that are present at each building or structure served shall be bonded together to form the grounding electrode system. Where none of these grounding electrodes exist, one or more of the grounding electrodes specified in 250.52(A)(4) through (A)(8) shall be installed and used.




(2) Metal Frame of the Building or Structure. The metal frame of the building or structure that is connected to the earth by any of the following methods:
(1) 3.0 m (10 ft) or more of a single structural metal member in direct contact with the earth or encased in concrete that is in direct contact with the earth
(2) Connecting the structural metal frame to the reinforcing bars of a concrete-encased electrode as provided in 250.52(A)(3) or ground ring as provided in 250.52(A)(4)
(3) Bonding the structural metal frame to one or more of the grounding electrodes as defined in 250.52(A)(5) or (A)(7) that comply with 250.56
(4) Other approved means of establishing a connection to earth

does your metal structural members meet the requirements above if not it is not a grounding electrode.

however it must still meet 250.104 (C)

(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.


Likely to become energized is open to interpretation.

 

[augie47]

Locally you would need to attach 1 time.

 

[justin59]

250.50 Grounding Electrode System.


however it must still meet 250.104 (C)



Likely to become energized is open to interpretation.

this is the one that I was concerned about. I guess since its a wood framed building and if I don't strap any conduits or boxes directly to the isolated steel structure, then it wouldn't be likely to become energized.