What would happen?

Inspection yesterday (30th) the service panel had “grounding conductors” and “grounded conductors” together on the bus bars under one screw. I told client this was a safety issue and should be looked at (although I see this quite often up here) the house is ten years old and this is original wiring. Client asked me what could happen if wiring left like that? I don’t really know? What could happen and what should I have told client?

Probably nothing, but the two wires (grounded and grounding) are not permitted in the same hole but they are permitted on the same bus. You were correct to point that out. It’s an actual NEC violation too.

[FONT=Helvetica-Bold][size=2]Can [/size][/FONT][size=2][FONT=Helvetica-Bold]I install the [/FONT][/size][size=2][FONT=Helvetica-Bold]neutral and ground conductor in the same termination?[/FONT][/size]

Nice resource. As the document mentioned this has been part of the UL listing standard for quite some time. However, since many electricians are unfamiliar with every nuance of the listing standard it was highly ignored. The inclusion of the actual standard in the NEC has made this prohibition much clearer for the installer who is more familiar with the requirements of the electrical code.

It can cause a poor connection, which can lead to overheating of the conductors like this.


The larger of the issues with this type of installation that with more and more multi-wire branch circuit installations going on the risk of someone pulling loose a common neutral (grounded conductor) and creating a 240V series circuit is highly at risk. Another factor is that many times the installers may use two different sized conductors which makes it hard to compress the proper torque on conductors of different circular mils thus potentially leaving one with a poor connect when it is really needed…and I wont elaborate on that.

While the manufacturers have been clear on this via UL 67 for many years and with talking with Eaton quite a bit, the practice should be discontinued and actually why it made it into the 2002 NEC directly to help encourage what manufacturers already want.

Thanks everyone, I can now give a fairly intelligent answer when they ask me about what would happen. I sometimes would do a nice little jig and try to distract them but NO MORE!

When did they decide the neutrals and grounds should not go under the same teminal? I see in Pauls answer that in 2002 the NEC changed this. Is that when they officially put it in writing that they could not go together under one terminal? thanks again


As I stated in a previous post it has always been part of the UL listing of the equipment. By inserting it directly into the NEC wording it will be read by a much broader audience of electricians. Many electricians had never even read a UL listing standard.

Thank you Robert, right in front of me!

I just ask electricians, why do they have all those screws on a buss bar if you are not suppose to use them?](*,)

Their reaction is :shock: