Re: Simple EMT fill calculation..HELP!
Jack how are you doing today.
First in regards to 17 - 12 AWGs in 3/4" EMT that is over the 40% fill limit regardless of the amperage.
I have to ask how far you where able to do this.
Certainly not much length or many bends.
The issue of separate circuits on a common neutral, as are most things this is not a straight yes or no answer.
In general yes, on a 3 phase panel you can run a circuit from Phase A, B and C and use one neutral, this is a multi wire branch circuit and is actual considered by the NEC to be one circuit even though it can come from 3 separate breakers.
On single phase you can use 2 hots to one neutral.
Here is the NEC definition of this.
Branch Circuit, Multiwire. A branch circuit that consists of two or more ungrounded conductors that have a voltage between them, and a grounded conductor that has equal voltage between it and each ungrounded conductor of the circuit and that is connected to the neutral or grounded conductor of the system.
In commercial work multiwire branch circuits are quite common.
Now the other side they can have problems with non-linear loads (computers, amplifiers, some lighting) The neutral can get overloaded.
Also if the neutral breaks or is unspliced live on one of these circuits you could send over voltage to some of the connected loads.
You questions have been good ones and the members here will be glad to help out some one just getting their foot in the door.
Bob
