Terminations of Grounding & Bonding Equipment

[Paul W. Abernathy]

The termination of equipment grounding and bonding conductors must be by exothermic welding, listed pressure connectors of the set screw or compression type, listed clamps, or other listed fittings. Sheet-metal screws cannot be used to connect grounding (earthing) or bonding conductors or connection devices to enclosures.

Obervations- As Mr. Holt so well put on this....note that drywall screws or wood screws are not mentioned here as being prohibited in the 2002 NEC.

When the HI is browsing around in the ole' electrical panel have you ever seen nice shinny sheet metal screws wrapped with a EGC or on in the older panels when they TRY to add EGC's doing this...

Why it is a problem ( and personally why the wood screws and drywall screws are also wrong in my opinion even though the NEC does not call it out ) is because the threads on these types of screws to not make enough contact with the enclosure to ensure a good bond...pre-threaded holes do with at all points within the thread count...but not with the screws listed above.

In a situation where their is a fault and it travels through that "sheet metal " screw the lack of contact could provide a less efficiant bond...and could actually loose the effective bond.

Just figured you all would like to know...Educational Moments...

Images Courtesy of Mr. Mike Holt

[Paul W. Abernathy]

Bump.....

[Jeffrey R. Pope]

Welcome back Paul

[Paul W. Abernathy]

lol......Educational Fella....Only educational....

[Patrick Bolliger]

...

Better change that last thing I did...DANG!

[brian winkle]

Paul, is it true that when using a #10 machine screw it must be a 10/32 and not a 10/24? We have a er, well I'll just say strict, county inspector here who is always trying to nail us on trivia like this. Last week he grilled me on the thread count on my bonding screws.

[Paul W. Abernathy]

Brian,

Man, I would think that AHJ would have better things to do...lol....

Anyway the NEC states that the screw should be " Connection means that are listed, are part of listed equipment, or are exothermically welded are required to ensure a permanent and low -resistance connection"

Now the issue he is probably bringing up is if a screw is used that is not designed to work directly with the equipment...much like stated about machine screws and so on...the funny thing is as I believe I posted in another topic...the NEC does not specifically rule out Sheetrock Screws and so on.....just Sheet Metal Screws in the NEC 2002 Verbage....

My opinion would be...I would never use Sheet Metal, Sheet Rock or Wood Screws anyway.....BUT to his point I am sure he is trying to say if the equipment is machined for 10/32 screws ( 32 thread count Spacing ) then anything other than that is not per the manufacturers listing.....

However......I have YET to see an AHJ say anything about this in my everyday experience..so it would be one nit picky AHJ....Here is the deal....When you BUY these unit it is kinda standardized anyway so chances are most all green bonding screws and so on designed for this will meet the manufacturers specs.......he is pushing it a bit.....

has he turned anything DOWN because of this...?

[brian winkle]

"has he turned anything DOWN because of this...?" So far he has not caught me up on anything..............

The screws he was referring to were ones I had drilled and tapped into J & P boxes.

He also requires us to install a breaker holdown in the new Cutler Hammer meter combos that come from the factory without one on the backfed main, even though the code says "on field installed backfed devices"

[Paul W. Abernathy]

Bump....Good Info

[Paul W. Abernathy]

Bump Again...I was looking around and found this.......enjoy !

OPPS...did anyone notice I said Low Resistance Connection....thehehe..Shame on me.....Low Impedance Connection.....Love It...lol

[jtedesco1]

Originally Posted by brian winkle

Paul, is it true that when using a #10 machine screw it must be a 10/32 and not a 10/24? We have a er, well I'll just say strict, county inspector here who is always trying to nail us on trivia like this. Last week he grilled me on the thread count on my bonding screws.

2008 NEC 250.8

(5) Machine screw-type fasteners that engage not less than
two threads or are secured with a nut

(6) Thread-forming machine screws that engage not less

than two threads in the enclosure

[Paul W. Abernathy]

lol....the date on the original post was PRE-2008 NEC acceptance fella...lol

[jtedesco1]

Originally Posted by pabernathy

lol....the date on the original post was PRE-2008 NEC acceptance fella...lol

yes, ...... and in the 2008 NEC SECTION 250.8 includes this new requirement for anyone who is interested!

(5) Machine screw-type fasteners that engage not less than
two threads or are secured with a nut

(6) Thread-forming machine screws that engage not less

than two threads in the enclosure

[Paul W. Abernathy]

Most Excellent.......I wish more states would just JUMP right to the 2008 NEC and bypass all the redtape. In Virginia, we wont see the 2008 NEC until about 2010 or 2011...sad to say.....

[jtedesco1]

I just finished two one day 2005 NEC Changes seminar for a few counties in Virginia, and they said that they are adopting the 2005 NEC in March:

PS: I was also told that the utility company is responsible for most of the service equipment, and the AHJ has no say on this issue, can you expand?