The Electrical Code

215.4 Feeders with Common Neutral Conductor. So to understand this there must be thorough understanding of why we can share the neutral. To begin AC stands for Alternate Current. Alternate Current, in this example, means that the voltage goes from 0 volts to +120 volts back to 0 volts then to -120 volts. Then back to 0 volts. This is called a cycle, and there are 60 cycles in one second in the United States uses this standard. In Europe uses they use 50 cycles per second. I will go into further description of hertz in a blog all to it self. I feel that it is important enough to go through this. So when one phase is hot the other phase is not. And at some point they meet at 0. Meaning they don’t need the neutral at the same time. They can share it with out overloading the neutral.

If I have described this enough for you then you can skip the next part of this. So in a single phase system that we have in our homes there are two phases. The reason they call it single phase is because when one is hot the other is not. Look at that I am a poet and didn’t know it. Hahahah. Then you have commercial applications that have three phases. And again in this set up you can still share the neutral because when one is hot the other is at 0 volts and the other is at -120 volts.

Remember this happens 60 times per seconds we don’t see the lights flicker because it is to fast for the eye to see it. The code does not have the obligation to describe this to you or anyone because it is not a technical book. No theory is explained here.

“(A) Feeders with Common Neutral. Up to three sets of 3-wire feeders or two sets of 4-wire or 5-wire feeders shall be permitted to utilize a common neutral.

(B) In Metal Raceway or Enclosure. Where installed in a metal raceway or other metal enclosure, all conductors of all feeders using a common neutral conductor shall be enclosed within the same raceway or other enclosure as required in 300.20.”