If either of these breakers are on, both of these wires have power. I believe that makes this a multi-wire branch circuit and that, configured thusly, this is a multifeed and that that is dangerous. Is that right?
Background:
I bought this house three years ago and am trying to untangle some electrical problems that came with it. Learning as I go. I did not wire this panel — I bought it this way.
Explanation:
Using my voltage detector pen, I can determine that if either of these breakers is on, both of these wires have power. Also, I traced the wires up to where they exit the box in a cable, and although it's hard to see so I can't be 100% sure, I'm 99% sure that they are part of the same 3-wire cable. Using the pen again, if either of these breakers is on, the cable registers voltage.
My research suggests that this is a multi-wire branch circuit and would be OK except that the two breakers should be on different buses, which these are not. I'm just hoping to confirm that understanding so I can see about fixing it.
Thank you for any insights!
Best Answer
The evidence would suggest that it is an improperly wired multi-wire branch circuit. The two legs of the circuit are erroneously and dangerously shorted together somewhere. When a MWBC is properly wired, the only path from one leg to the other is through the loads.
The reason the two breakers are on the same pole is some delirious spark monkey discovered that if installed properly they trip instantly when main power is restored. He was unable to discover the real problem but by moving stuff around at random he effected a miracle cure.
The quickest test for a real short circuit, as opposed to a phantom voltage transmitted through the loads, is to properly position the breakers on opposite poles and see if they trip immediately.