grounding screw?

[jason32]

250.148(A) States that the EGC should be connected to a metal box by a Grounding screw, is there a code reference that defines this as machined with a green finish? I can't seem to find anything other than 250.126 which refers to device terminals. Fellow worker was discarding unused MC clamp and re-using the screw to fasten EGC to box. Just doesn't seem right.

 

[bphgravity]

Re: grounding screw?

No, the code does not require the screw to be green. See section 250.8 This section does say "or other listed means". I don't know if a screw from a connector would qualify?

 

[petersonra]

Re: grounding screw?

You can't use a sheet metal screw, but a machine screw ought to be OK. i am not sure if there is any color requirement.

 

[hbiss]

Re: grounding screw?

Nope, there is no requirement that the screw be green or anything else other than it be a machine screw threaded into a hole in the box and not hold anything else. I would have to look but there is a minimum number of threads relative to the thickness of the box material and it cannot be self tapping.

A 10-32 clamp screw fits the requirements just fine.

-Hal

 

[electricmanscott]

Re: grounding screw?

A classic if ever there was one.
http://electrical-contractor.net/ubb/Forum2/HTML/001478.html
Be prepared to read!
And if youre eyeballs don't fall out of your head there's more!
http://electrical-contractor.net/ubb/Forum2/HTML/001492.html

 

[johndeereman]

Re: grounding screw?

Art.250.8 States how you are to make the connections. If you look @ Art.250.126 states the way the identifacation of the terminals are to be on devices & this is were the green screw comes into play. I hope this helps.

 

[peter d]

Re: grounding screw?

Originally posted by jason32:
Fellow worker was discarding unused MC clamp and re-using the screw to fasten EGC to box. Just doesn't seem right.

It may not seem right if you were trained a certain way, but there is nothing wrong with what your coworker is doing as far as the NEC is concerned.

 

[kilewatt2002]

Re: grounding screw?

I was looking at the screw issue & see all points were covered. As for using a set screw, my only question would be if the screw was long enough. I believe that the machine screw is to have 16 complete threads (I'm not sure on this statement so excuse me if Im wrong)

Glenn

 

[don_resqcapt19]

Re: grounding screw?

John,

Art.250.126 states the way the identifacation of the terminals are to be on devices & this is were the green screw comes into play.

That section only applies to the grounding screw on the device itself. It does not apply to the screw used to connect the EGC to the metal box.
Don

 

[hurk27]

Re: grounding screw?

By Glen: I believe that the machine screw is to have 16 complete threads

So a 8/32 would have to be only screwed in to a panel that is ?" thick? (8/32 would have 32 threads per inch which 16 threads of it would be a ?")
I think it was stated once in here that there needs to be at least 3 threads in contact? I'll have to find the thread (no pun intended) :roll: it was awhile ago.

By Hal: it cannot be self tapping.

Self tapping machine screws are used all the time for making grounding connections. most all MBJ's are a self tapping tapered threaded screw as well as the screws that are in the grounding tails we use for bonding box's. There is nothing that say's this in the code. A self tapping machine screw is not a sheet metal screw.

 

[physis]

Re: grounding screw?

A 4 sq. box made of 1/16 material only has two threads in contact with an 8-32.

 

[benaround]

Re: grounding screw?

I've never seen more than one thread on any machine screw,no matter what the length is!!

frank

 

[buck33k]

Re: grounding screw?

Granted, the screw from the MC connector would work fine when fastening a grounding buss or lug to the metal enclosure, but I'm not sure I'd wrap a conductor around it. The flange on the green grounding screw is 20% wider by my measurement. It sounded like Jason32's fellow worker was going directly to the box with the EGC using the mc screw. Although there may be no restrictions concerning this, it doesn't sound like the best connection to me.
I tried to find a box of green screws out in the truck to look for a UL listing, but no luck.
Buck

 

[wmhwdh00]

Re: grounding screw?

I think the word listed is the most important thing to look at. If the screw is not listed (tested) for the purpose then it can not be used no matter how many threads are sticking thru.

 

[don_resqcapt19]

Re: grounding screw?

wmhwdh00,

I think the word listed is the most important thing to look at. If the screw is not listed (tested) for the purpose then it can not be used no matter how many threads are sticking thru.

I can't find a UL listing for "grounding screws" or a box of green screws with a listing mark.
Don

 

[charlie]

Re: grounding screw?

What color is a green grounding screw? HMMM

OK, now to get serious. There are no listed grounding screws. However, you can find bags of #10-32 screws in plastic bags that are sold as grounding screws. In other words, you are permitted to use a #10-32 machine screw for grounding but you may not use a sheet metal screw for grounding.

Sorry, I couldn't resist saying the first line.

 

[ryan_618]

Re: grounding screw?

Originally posted by electricmanscott:
A classic if ever there was one.
http://electrical-contractor.net/ubb/Forum2/HTML/001478.html
Be prepared to read!
And if youre eyeballs don't fall out of your head there's more!
http://electrical-contractor.net/ubb/Forum2/HTML/001492.html

Boy does that take me back! I remember Charlie and I talking about this in a hotel bar in Salt Lake just about a year ago. Thanks for posting the link Scott.

 

[luke warmwater]

Re: grounding screw?

Originally posted by ryan_618:
I remember Charlie and I talking about this in a hotel bar in Salt Lake just about a year ago.

A great place to discuss such things, indeed! hiccup.

Scott,
the links were scary for sure.

 

[jimwalker]

Re: grounding screw?

Just had this issue brought up a couple days ago with a fellow worker.Seems when one of our men made up some AC disconnects they didn't know what to do with that green screw so kept it or throwed it away.My job was to inspect the building before we call the county.We had some machine screws 2 inch #10s so we used green marker and made some.But i pointed out to him that the code never said it SHALL be green.His reply was an inspector told him it must be.He thought he had read it but now not sure.So now we would like a code backed answer preferably in black and white and not mud brown or gray

 

[charlie]

Re: grounding screw?

The only references I know of for a green screw are 250.28(B), 250.126, and 406.9(B).