Hello to all,
I'm looking for help in answering a question that has been posed elsewhere on the 'net. This was mainly asked concerning a single-phase residential install, but it could have applications elsewhere.
Would it be allowable (stictly from a code standpoint) for two circuits to share a common grounded conductor if they were fed from the same leg of the service and if the grounded conductor were sized properly for the maximum load? For example two 15A 120V circuits sharing a #10 copper grounded conductor.
My first thought was no but when I tried to find a specific code reference, I was unable to do so. Since there is no voltage between the two ungrounded conductors in this arrangement, it doesn't satisfy the definition of a multiwire circuit and in my mind the requirements for multiwire circuits couldn't be enforced. Likewise, since the grounded conductor would not be carrying the unbalanced current of two (or more) ungrounded conductors I don't think it could be called a neutral. Everything that I found that I thought might apply to this situation used one or both of those terms. With that in mind, I was unable to find anything that specifically prohibited or regulated this type of installation.
This would all just be a mental exercise, but when thinking about it I began to see some potential problems. For example, IF this is not specifically prohibited and IF it is not required to follow the rules for multiwire circuits (because it doesn't satisfy the definition of a multiwire circuit), then it would be possible for someone to supply split wired receptacles with this arrangement without complying with 210.4(B).
In reality, this doesn't seem like a practical way of running two circuits but I do see where someone could try to apply it. In my mind this should be either prohibited by code or if allowed, it should have to meet the requirements for multiwire circuits.
This may be in the code and I have just missed it. If so, I'll be embarrassed but relieved. Hopefully you guys can straighten me out on this.
Thanks in advance,
Jim
[This message has been edited by jb (edited 06-26-2003).]
