12ga and 14ga under same screw on ground bar

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sweetcav

Member
Location
Central Pa
One of my guys got hit for putting a 12 and 14 under same screw, tried looking up a code article for it, but on road right now, is there a code article for this or is it just good workmanship.
 

bphgravity

Senior Member
Location
Florida
Section 110.14(A) of the NEC:
Terminals for more than one conductor and terminals used to connect aluminum shall be so identified.

The UL486 standard permits the termination of two or more conductors and conductors of different CMs, but they need to be tested and certified that way, and then marked or identified for those sizes and combinations.
 

qcroanoke

Sometimes I don't know if I'm the boxer or the bag
Location
Roanoke, VA.
Occupation
Sorta retired........
One of my guys got hit for putting a 12 and 14 under same screw, tried looking up a code article for it, but on road right now, is there a code article for this or is it just good workmanship.

If they were neutrals only 1 allowed per hole.408.41 NEC 2014
Different sizes under same screw I'm not really sure about.
 

Carultch

Senior Member
Location
Massachusetts
One of my guys got hit for putting a 12 and 14 under same screw, tried looking up a code article for it, but on road right now, is there a code article for this or is it just good workmanship.


Terminals need to be rated for the type of metal in the conductor.
Terminals need to be rated for the size range the conductor.
Terminals need to be rated for the temperature ampacity column, otherwise 110.14(C)'s defaults apply.
Terminals need to be rated for more than one conductor, otherwise are by default rated for only one.

Most terminals rated for multiple conductors are able to accept any mix of sizes within range, provided that it is either all copper, or all aluminum.
Few (if any) are rated for mixing copper and aluminum, and usually would have a physical separator.
 

sweetcav

Member
Location
Central Pa
These are both copper conductors, they are just worried that since they are torqued to 20 in lbs the 12 would be torqued better than the 14. It is a siemens panel, I will have to check the instructions when I get back
 

iwire

Moderator
Staff member
Location
Massachusetts
These are both copper conductors, they are just worried that since they are torqued to 20 in lbs the 12 would be torqued better than the 14. It is a siemens panel, I will have to check the instructions when I get back

The directions most likely allow two conductors of the same size.

As far as a code section I would say 110.3(B).
 

jim dungar

Moderator
Staff member
Location
Wisconsin
Occupation
PE (Retired) - Power Systems
Most terminals rated for multiple conductors are able to accept any mix of sizes within range...

Terminals that have one conductor on each side of the screw are often capable of accepting different size conductors, however those that use a single hole without a pressure plate, like those on a ground bar, commonly require the conductors to be the same size.
 

rubink33

Member
Location
Arizona USA
Most panels and ground bars have manufacturer specs that you will go off of it tells you what can and can not do and if there isn't one then I would just go for the sure thing and put one per hole.

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