Multiple Wires Under a Set Screw Neutral Bar

[djcrzysounds@yahoo.com]

I received a service call about a 'bad breaker'. I opened the panel cause I heard an arcing noise. Part of a Square D Neutral bar was beginning to melt. Long story short. There were 3 wires under the terminal screw, 2 Grounded Conductors and a Ground. The panel is the main. What and where does the NEC state that it has to be one wire per terminal in the panel, or is that part of the UL Listing? Also what is everyones feelings about more than one wire under a terminal.

 

[chevyx92]

I received a service call about a 'bad breaker'. I opened the panel cause I heard an arcing noise. Part of a Square D Neutral bar was beginning to melt. Long story short. There were 3 wires under the terminal screw, 2 Grounded Conductors and a Ground. The panel is the main. What and where does the NEC state that it has to be one wire per terminal in the panel, or is that part of the UL Listing? Also what is everyones feelings about more than one wire under a terminal.

Suppose to be listed for more than one under one terminal. Theoretically it will work with more than one, same as a splice! Not saying it's ok.

 

[lucky1974]

Cant have more than one grounded conductor under a screw hole.408.41

 

[JohnJ0906]

Cant have more than one grounded conductor under a screw hole.408.41

True.

Multiple EGCs are allowed under one screw, provided the panel is rated for it. Most modern load centers that I am aware of will allow 2 or 3 #14s/#12s.

 

[weressl]

I received a service call about a 'bad breaker'. I opened the panel cause I heard an arcing noise. Part of a Square D Neutral bar was beginning to melt. Long story short. There were 3 wires under the terminal screw, 2 Grounded Conductors and a Ground. The panel is the main. What and where does the NEC state that it has to be one wire per terminal in the panel, or is that part of the UL Listing? Also what is everyones feelings about more than one wire under a terminal.

When you would unwire one circuit and attempt to remove the corresponding EGC, the equipment still in service would be unprotected while the wire to be abandoned is removed. In the case of neutrals it is even a bigger problem as you would need to shutdown the 'other' circuit as well. So as a general rule one EGC and neutral per set-screw.

 

[JohnJ0906]

So as a general rule one EGC and neutral per set-screw.

Do you mean "one EGC or neutral"?

 

[weressl]

Do you mean "one EGC or neutral"?

Yes and no, yes and no, yes and no. One EGC per each ground set screw and one neutral wire per each neutral set screw. Certainly don't suggest to terminate the EGC under the neutral set screw or vice versa.......

 

[macmikeman]

When you would unwire one circuit and attempt to remove the corresponding EGC, the equipment still in service would be unprotected while the wire to be abandoned is removed. In the case of neutrals it is even a bigger problem as you would need to shutdown the 'other' circuit as well. So as a general rule one EGC and neutral per set-screw.

I shut down the whole panel prior to removing wiring from busbars....

 

[weressl]

I shut down the whole panel prior to removing wiring from busbars....

From the neutral or ground bus? Really? How do you justify that.

 

[don_resqcapt19]

Yes and no, yes and no, yes and no. One EGC per each ground set screw and one neutral wire per each neutral set screw. Certainly don't suggest to terminate the EGC under the neutral set screw or vice versa.......

While you make a good point about why it would be a good practice to use one screw per EGC, the code and the listing does not normally require this. For most panel terminal bars the listing permits more than one EGC per screw.

 

[Dennis Alwon]

Yes and no, yes and no, yes and no. One EGC per each ground set screw and one neutral wire per each neutral set screw. Certainly don't suggest to terminate the EGC under the neutral set screw or vice versa.......

Before the code change on neutrals under individual screws I use to land the neutral with its corresponding egc under the same screw in the MDP. This made it easy if the wires needed to be replaced.

 

[Jim W in Tampa]

Heck why do we care if a circuit loses the ground for a minute or 2 ? What could happen in a few minutes ? At most we kill some one. NEC not always thinking things out.

 

[macmikeman]

From the neutral or ground bus? Really? How do you justify that.

Simple, I"m a pro.

 

[weressl]

While you make a good point about why it would be a good practice to use one screw per EGC, the code and the listing does not normally require this. For most panel terminal bars the listing permits more than one EGC per screw.

Hence my sig:

Just because it works it doesn't mean it's right!

 

[don_resqcapt19]

Before the code change on neutrals under individual screws I use to land the neutral with its corresponding egc under the same screw in the MDP. This made it easy if the wires needed to be replaced.

So you are one of the reasons for the code change. This rule was part of the listing instructions for many years before it became part of the code. The only reason it became part of the code is the fact that the installers were not reading and following the instructions provided on or with the panels.

 

[djcrzysounds@yahoo.com]

I look at everyone's justifications for either allowing it or disallowing it. I have always been one to land a Neutral and EGC under the same terminal. But as of late and seeing things like poor terminations I try to land every wire under their own set screw. I still can't believe the NEC has nothing that would require 1 wire per terminal. I feel it should be but I can't change everything. Well not yet atleast.

 

[Dennis Alwon]

So you are one of the reasons for the code change. This rule was part of the listing instructions for many years before it became part of the code. The only reason it became part of the code is the fact that the installers were not reading and following the instructions provided on or with the panels.

Guilty as charged.

 

[steelersman]

Certainly don't suggest to terminate the EGC under the neutral set screw or vice versa.......

Certainly don't suggest that in a main panel that there are seperate bars for neutral and ground. They are all on the same bar or bars.

 

[weressl]

I look at everyone's justifications for either allowing it or disallowing it. I have always been one to land a Neutral and EGC under the same terminal. But as of late and seeing things like poor terminations I try to land every wire under their own set screw. I still can't believe the NEC has nothing that would require 1 wire per terminal. I feel it should be but I can't change everything. Well not yet atleast.

There supposed to be a separate neutral bus and a ground bus. Although some people suggested color distinciton, like one should be uncoated copper and the other tin plated, since aluminum is commonly used that distionction is impractical. But you can always distinguish the neutral bar since it is mounted on insulators, while the ground bus has galvanic connection to the housing/packplane and bonded to it or to the throughwall grounding bolt.

 

[daleuger]

I shut down the whole panel prior to removing wiring from busbars....

Good practice if that's feasible. We can all work a hot panel but prefer not to if it can be avoided, but what about if you're working in an existing building where they need it to be on?