Two wires under one screw... loophole

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Srv52761

Srv52761

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lowa
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Energy Manager
Seriously.
While replacing a switch in a metal 4” square box, I noticed the ground wire was not pigtailed to the box.
Instead, it was cut a little long, looped around the ground screw, then continued to the switch. Does this circumvent the concept of two wires under one screw? Is this code compliant? Seems you couldn’t get even pressure on the conductors.
 
No, it's only one wire. (And it's really common practice.)
AFAIK, yes.

There's nothing that says that a loop of wire can't continue to another terminal. The problem is more from trying to get two separate conductors under the one screw. If the wires are small enough to twist and loop (<18g stranded, for audio), it might work, but not with the usual building wire.
 
I've done that occasionally with the hot wire even on multi-gang switches and receptacles. Use t-strippers to cut then slide the insulation just enough to hook a screw. Usually when I ran out of the correct size wire nut for the number of wires I was combining at the end of the day and the end of the job.
 
Did that a lot.
Cut down on wire nuts taking up space too.
Would that be considered 1 wire?
 
There is no loophole, it's one conductor and permitted by the NEC. Also a fairly common practice.

BoxFillCalculationNEC_314SwitchesReceptaclesGroundsStrapsYokesWireNutsClampsMikeHoltPigtailsDoNotCount.jpg
 
gadfly56 said:
Wiring up fire alarm devices, this practice is a big no-no.
Click to expand...
What practice is a big no no?


Srv52761 said:
it was cut a little long, looped around the ground screw, then continued to the switch. Does this circumvent the concept of two wires under one screw? Is this code compliant? Seems you couldn’t get even pressure on the conductors.
Click to expand...

Why is there uneven pressure on the conductors? What was the other conductor? There is only one conductor with this method. Was the copper crossed over itself, as in more than a 360° wrap? That would not be good. I do a ~300° wrap, and all is well.
 
Think about the end of the wire being looped around the screw. Doesn't that have the same amount of contact as the one pictured above.
 
Frank DuVal said:
What practice is a big no no?




Why is there uneven pressure on the conductors? What was the other conductor? There is only one conductor with this method. Was the copper crossed over itself, as in more than a 360° wrap? That would not be good. I do a ~300° wrap, and all is well.
Click to expand...
Looping the wire under a screw. This is more an issue for conventional appliances. Since fire alarm devices are supervised, if the loop pops out from under the screw the panel thinks the device is still supervised.
 
gadfly56 said:
Looping the wire under a screw. This is more an issue for conventional appliances. Since fire alarm devices are supervised, if the loop pops out from under the screw the panel thinks the device is still supervised.
Click to expand...
Yes that's the reason the conductor must be cut, so that if the binding screw or a wire came out you would lose the supervisory loop and get a trouble alarm.
 
Frank DuVal said:
..... Why is there uneven pressure on the conductors? What was the other conductor? There is only one conductor with this method. Was the copper crossed over itself, as in more than a 360° wrap? That would not be good. I do a ~300° wrap, and all is well.
Click to expand...

Yes, in the the box I opened the ground wire was wrapped more than 360°.
 
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