FERROUS OR NOT?

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PEDRO ESCOVILLA

Senior Member
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south texas
I SEE THINGS UNFAMILIAR TO ME. ONE THING I SEE IS CONDUIT (EMT) PROTECTING THE GEC TO THE GROUND ROD, (ONLY ONE HERE, THATS A CURIOSITY, WHY NOT TWO?) BUT NO BONDING BUSHING IN THE PANEL, AND NO CHOKER AT THE BOTTOM END? I ASKED THE BO ABOUT THIS, AND "HE'D NEVER HEARD OF IT". I'M STILL WAITING FOR HIS REPLY TO MY CODE REFERENCES. AM I COMING FROM THE WRONG PLACE ON THIS, EMT IS FERROUS IS IT NOT? IF SO, IT NEEDS TO BE BONDED AT BOTH ENDS WHERE IT PROTECTS THE GEC. :angel:
 
You are correct and it seems someone down there needs an education. I use PVC so I don't have to bond both ends,

BTW- welcome to the forum. Also please type without caps locks on--
 
250.64

(E) Enclosures for Grounding Electrode Conductors.​
Ferrous metal enclosures for grounding electrode conductors
shall be electrically continuous from the point of attachment
to cabinets or equipment to the grounding electrode
and shall be securely fastened to the ground clamp or
fitting. Nonferrous metal enclosures shall not be required to
be electrically continuous. Ferrous metal enclosures that are
not physically continuous from cabinets or equipment to
the grounding electrode shall be made electrically continuous
by bonding each end of the raceway or enclosure to the
grounding electrode conductor. Bonding methods in compliance
with 250.92(B) for installations at service equipment locations
and with 250.92(B)(2) through (B)(4) for other than
service equipment locations shall apply at each end and to all
intervening ferrous raceways, boxes, and enclosures between​
the cabinets or equipment and the grounding electrode.
Click to expand...

Show the boss this.
 
At the service panel it is bonded by virtue of the main bonding jumper. I do not feel additional bonding at the service panel end is needed.
 
iwire said:
At the service panel it is bonded by virtue of the main bonding jumper. I do not feel additional bonding at the service panel end is needed.
Click to expand...
As long as the EMT is continuous from the bond on the ground rod end all the way to the EMT connector that is tightly secured in the knockout of the steel (ferrous metal) of the service panel, then the bond at the service panel is already in place where the GEC is tied to the panel steel enclosure by the Main Bonding Jumper (MBJ).

The key, to the bonding both ends requirement in 250.64 is that the ferrous raceway and enclosure is electrically continuous through tight EMT fittings. Look at that second sentence in 250.64.

The physics involved causes a current to flow in the steel, when the current is flowing in the GEC. To maintain the efficiency of the physically protected GEC the current has to travel on BOTH the wire and the pipe. The MBJ to panel enclosure to EMT connector to EMT path is the service panel end bond.

Now, if the EMT used for physical protection of the GEC is just a short segment on the outside of the building, then the EMT segment (that is not electrically continuous to the MBJ) has to be bonded at both ends to the GEC wire. Then the wire and the EMT segment can share carrying the current.
 
I like pictures.

GECpipe.jpg
 
FERROUS OR NOT?

Section does require the ferrous wiring method to be bonded at both ends per 250.94(B), so to keep from using a grounding bushing and bonding jumper you would have to use grounding lock-nuts.
 
jumper said:
I like pictures.

GECpipe.jpg
Click to expand...

I like pictures as well but IMO that one shows more than required.

cripple said:
Section does require the ferrous wiring method to be bonded at both ends per 250.94(B), so to keep from using a grounding bushing and bonding jumper you would have to use grounding lock-nuts.
Click to expand...

There is no requirement to bond it twice at the service panel.

The EMT is bonded to the GEC via the main bonding jumper in the panel.
 
Considering the Mike Holt graphic that Derek (Jumper) posted - make the EMT run long enough that a 4" square metallic j-box is included somewhere between the service center panel and the ground rod end.

Based upon the implied guidance in the Mike Holt graphic, are you going to install a bond from EMT to EMT in the 4" j-box?
 
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