Stranded Wire under box ground screw

Flex

Senior Member
Location
poestenkill ny
Anyone know of a code that doesnt allow you to wrap stranded wire around the box ground? I know the premade groundtails they sell use solid wire. I prefer to use solid but I recently had a job with alot of long homreuns and chose to use stranded. The few that have boxes with splices in them I just used one of the incoming stranded greens to bond the box. Felt getting a solid tail would be wasting time.
 
There has been discussion on this I believe the NEC is silent on this. However, it is a listing issue. If it is listed for stranded wire then you are OK. If i remember correctly.
It is a care and skill issue. Before terminating, one should make sure that the twisting of the stranded wire remains and many electricians choose to just hand twist it even more than the original and when you're bearing down on the loop with the screw, make sure that all the strands remain under the head and you don't have oppurtunistic 'flyers' sticking out 'waiting' to pierce a phase wire insulation pressed against it.
 

masterinbama

Senior Member
I always strip about 1/4 " more than needed then restrip 1/4" of insulation and pull it until it is at the end of the wire. This little 1/4" piece of insulation keeps the strands grouped and makes for a better termination.

You also need to keep in mind if you use field installed crimps that you make sure they are listed for grounding. (some aren't)
 

Little Bill

Moderator
Staff member
Location
Tennessee NEC:2017
Occupation
Electrician
I have done this for years with stranded wire. Twist the wires counterclockwise then wrap around the screw. The strands won't come apart when tightening the screw this way.
 

kwired

Electron manager
Location
NE Nebraska
There has been discussion on this I believe the NEC is silent on this. However, it is a listing issue. If it is listed for stranded wire then you are OK. If i remember correctly.
Listing of what? Grounding screws are not listed, and are not required to be either. This has been mentioned a few times on this forum before, if it is wrong please provide some references.



masterinbama-

Where do you find these terminals that are listed for grounding? I did some searching and come up with nothing so far.
In a PDF catalog for T&B I did a search for the word "ground" and had zero hits. My Google searches come up with anything but what I was trying to find.
 
I always strip about 1/4 " more than needed then restrip 1/4" of insulation and pull it until it is at the end of the wire. This little 1/4" piece of insulation keeps the strands grouped and makes for a better termination.

You also need to keep in mind if you use field installed crimps that you make sure they are listed for grounding. (some aren't)
The Pro's pro:lol:
 

edward

Senior Member
Listing of what? Grounding screws are not listed, and are not required to be either. This has been mentioned a few times on this forum before, if it is wrong please provide some references.
What i meant is the device has to be listed not the screw.

I believe if it not listed as "solid Only" then it is ok to wired with stranded conductor.

i am looking in the white book see if i can find anything.

Here is link that limits the side screws to solid wires only. Residential grade.

Here is a link that allows solid and stranded.

Here is a spec grade that allows both
 
Last edited:

kwired

Electron manager
Location
NE Nebraska
What i meant is the device has to be listed not the screw.

I believe if it not listed as "solid Only" then it is ok to wired with stranded conductor.

i am looking in the white book see if i can find anything.
Terminal screws on devices has been talked about on here before - they are acceptable for stranded conductors.

This thread is about stranded wire under the ground screw in the back of the outlet box not the device screws.
 

edward

Senior Member
Terminal screws on devices has been talked about on here before - they are acceptable for stranded conductors.

This thread is about stranded wire under the ground screw in the back of the outlet box not the device screws.
Sorry, I misread the OP post. I thought it was about a device.

apologize. i need to pay more attention.
 

masterinbama

Senior Member
masterinbama-

Where do you find these terminals that are listed for grounding? I did some searching and come up with nothing so far.
In a PDF catalog for T&B I did a search for the word "ground" and had zero hits. My Google searches come up with anything but what I was trying to find.


I bought some that specifically said not listed for equipment ground termination. (or something to that effect).


Usually if they don't say they are not, they are.
 

kwired

Electron manager
Location
NE Nebraska
I bought some that specifically said not listed for equipment ground termination. (or something to that effect).


Usually if they don't say they are not, they are.
If they are listed for grounding there has to be listing documentation somewhere otherwise how do we know it is listed?

They may or may not be required to be marked but something has to exist to be able to say they are indeed listed.
 

kwired

Electron manager
Location
NE Nebraska
If I'm using stranded wire. I prefer to use the crimp on forked terminals. Its a good solid connection.
Seems like it would be good and solid. But to be truthful I think I have seen more of those fail than I have seen conductors wrapped around a screw fail.
 

don_resqcapt19

Moderator
Staff member
Location
Illinois
Occupation
retired electrician
Wire connectors, either crimp or wire nut types are not required to be listed for bonding and grounding when used to terminate grounding and bonding conductors. See 250.8(1). This was added in the code because without it there would only be one wire nut that you could use with grounding conductors as the green wire nut is the only one listed for that purpose. (both wire nuts and crimp connectors are pressure connectors and covered by the same UL Guide Information sheet, ZMVV)
 

jim dungar

Moderator
Staff member
Location
Wisconsin
Occupation
Retired Electrical Engineer - Power Systems
Wire connectors, either crimp or wire nut types are not required to be listed for bonding and grounding when used to terminate grounding and bonding conductors. See 250.8(1). This was added in the code because without it there would only be one wire nut that you could use with grounding conductors as the green wire nut is the only one listed for that purpose. (both wire nuts and crimp connectors are pressure connectors and covered by the same UL Guide Information sheet, ZMVV)
Isn't that all 'voltage rated' connectors can also be used on grounding conductors, but 'grounding rated' connectors can be used only for grounding.

Ideal kind of forced this new category when they put the hole in the top of their 'greenie'.
 
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