Bond Bushings For GEC?

[The Iceman]

Just when I thought I had grounding and bonding down I came across this: A large sign had a combination 100A meter/panel mounted on the steel column base. In the back of the panel there was a 1" metallic chase nipple going into the steel colmn for the three branch circuits feeding the sign. They also took the # 6 AWG GEC through the same 1" metallic chase nipple, down the inside of the steel column, and to the ground rod.
Is this a violation of 250.64 (E)? I'm thinking this 1" metallic chase nipple should have bond bushings installed for the #6 GEC.

 

[stretch12]

are they on line or load side of ocp line need bond load plastic will do

 

[stickboy1375]

 

[The Iceman]

Stick I'm thinking because the #6 AWG passes through the 1" metal chase nipple it would need bond bushings.

 

[stickboy1375]

Stick I'm thinking because the #6 AWG passes through the 1" metal chase nipple it would need bond bushings.

And I agree with you.

 

[stickboy1375]

are they on line or load side of ocp line need bond load plastic will do

The OP was asking about the GEC.

 

[stickboy1375]

Here is a good explanation on why the ferrous raceway must be bonded,


Ferrous (iron/steel) raceways, boxes, and enclosures containing the grounding electrode conductors must have each end of the ferrous metal raceway, box, and enclosure bonded to the grounding electrode conductor [250.92(A)(3)]. ?Nonferrous? metal raceways, such as aluminum rigid metal conduit, enclosing the grounding electrode conductor aren?t required to meet the ?bonding each end of the raceway to the grounding electrode conductor? provisions of this section.

The bonding jumper must be sized no smaller than the enclosed grounding electrode conductor. Caution: The effectiveness of the grounding electrode can be significantly reduced if ferromagnetic raceway containing a grounding electrode conductor isn?t bonded to the grounding electrode conductor at both ends. This is because a single conductor carrying high-frequency lightning current in a ferrous raceway causes the raceway to act as an inductor, which severely limits (chokes) the current flow through the grounding electrode conductor. ANSI/IEEE 142, Recommended Practice for Grounding of Industrial and Commercial Power Systems (Green Book) states, ?An inductive choke can reduce current flow by 97%.? To save a lot of time and effort, simply run the grounding electrode conductor exposed if not subject to physical damage [250.64(B)], or enclose it in a nonmetallic conduit that is suitable for the application.


http://ecmweb.com/nec/code_top50nec_012607/

 

[Dennis Alwon]

Would the metal column be also considered a ferrous raceway and would you have to bond the GEC where it exits the column?

 

[The Iceman]

And I agree with you.

Even a nipple? I know that lightning causes excessive heat in a non-bonded metal raceway and could melt the GEC in two. But even a metal chase nipple?

 

[The Iceman]

Would the metal column be also considered a ferrous raceway and would you have to bond the GEC where it exits the column?

I was also wondering this. And way install a GEC for a panel mounted on a 12"+ steel column that is bolted to a concrete base in the ground? With the cost of copper and labor seems pointless.

 

[stickboy1375]

I think trying to provide protection against lightning at all is pointless. :wink:

 

[buck33k]

Would the metal column be also considered a ferrous raceway and would you have to bond the GEC where it exits the column?

I would say so.

 

[buck33k]

I was also wondering this. And way install a GEC for a panel mounted on a 12"+ steel column that is bolted to a concrete base in the ground? With the cost of copper and labor seems pointless.

IMO It would'nt be necessary to bring a GEC down the steel post. From the service panel a short GEC could hit the steel post(structure). If 10' of steel post were not in contact with the earth, another bonding jumper could connect the base to other electrodes.