Panel: 1 neutral per lug

Does someone have an educational resource why you want 1 neutral per lug? I was working on my comment for this and am having a hard time trying to explain why you can have 1 neutral per lug.

Thank you in advance,

Stephen Rager

try this .

The NEC added language into the code to prohibit this practice even though it was already prohibited by the listing of the panelboard neutral bar.

This is an explanation from Mike Holt:

That was very detailed. Thank you for posting.

I usually tell them reason is very complicated and technical. The bottom line is that double tapping/lugging a neutral is not acceptable. There is a really good illustration in the link below.

Robert is correct…
408.41 Grounded Conductor Terminations. Each grounded conductor shall terminate within the panelboard in an individual terminal that is not also used for another conductor.
Exception: Grounded conductors of circuits with parallel conductors shall be permitted to terminate in a single terminal if the terminal is identified for connection of more than one conductor.

If two grounded (neutral) conductors were connected to the same terminal, and someone removed one of them, the other might unintentionally be removed as well. If that happens to the grounded (neutral) conductor of a multiwire circuit, it could result in excessive line-to-neutral voltage for one of the circuits.

These are all great explanations, to someone who understands electricity, and how and why it works. Talk imbalanced loads, and straying neutral conductores to a 60 year old widowed housewife will get you the deer-in-the-headlights look.

I just make it simple for them." When more than one wire is under a terminal, one can become loose, and start to corrode, and/ or spark from a loose connection. It should be repaired by a qualified electrical contractor."

If the detailed explanations are too complicated, just tell them this can happen

Zactly!! :stuck_out_tongue:

The same thing could happen with only a single conductor in a loose terminal. This is not limited to multiple conductors.

That’s correct, however he’s trying to get a point across and the likelihood is significantly greater when conductors are doubled or tripled up. IMO: most people don’t realize that the grounded conductors are current carrying.

Correct, that burnt conductor in the photo is the only conductor in the hole and since it’s in the bottom of the hole I would guess that it was never tightened.

So are you two claiming that double lugging of grounded terminals is not a contributing factor in some instances of overheating terminal connection?

I’m not, I won’t speak for Jim. IMO a single conductor per hole is an excellent requirement especially with older homes that may have MWBC’s.

Then I’m unclear exactly what point you are trying to make in this thread.

Give me a specific post and I’ll explain.

Some seemed to be making the point that this issue is limited to doubled grounded conductors. I was simply saying that it is not. I have worked in many many panels that had doubled neutrals or neutrals and ground mixed with absolutely no problems outside of the code or listing issue.

Who is some? I don’t know anyone named some. I’ve seen thousands of installations with double lugged neutrals that exhibited no apparent ill effects or thermal exceptions…

You might get away with running across a six lane highway any number of times without incident or you might get run over the first time that you walk across a school crosswalk. That doesn’t put the two activities in the same risk category. When you tell your child not to run across the highway, does it really matter that his friend did and lived to tell about it or that he knows of someone who got hit in the school crosswalk? No.

The odds of having a loose or high resistance connection that produces excessive heat are higher when you place multiple current carrying conductors under a lug rated for one conductor than when you have a single conductor under the screw. It’s not an absolute and it’s not a prediction, hence the use of the word “can” vs. “will”.

Multiple neutral conductors in a single termination create a significant problem as they may become loose or when loosening of two neutrals under the same lug under load for repairs is a safety hazard.

There is too much controversy when trying to reason out the technical facts with clients. Its best to stick to simple straight up reasoning - “NEC does not allow double tapping of neutrals” - and let the electrician explain it to them if need be.

Here are some examples of controversial tidbits,

  • It is lawful and okay to double tap grounds, the screws on bus bars are made and listed for it.
  • If I had a dollar for every double tapped breaker that an inspector wrongfully wrote up when it actually was not a fault I’d be rich, because many many many breakers are listed and made for it.
  • A 12-3 wire can lawfully feed two separate circuits with its red and black ungrounded conductors connected to their own breakers, and lawfully share a common neutral.

All these facts and more are available to drag out conversations farther than they need to be.

Home inspectors are not code compliance inspectors.