I’m trying to under stand what the problem here is. It’s hard to follow but these two breakers (circuits) share a single neutral (MWBC?). One problem is that they look to be on the same phase (?), am I correct on that? another problem is that you can turn off the power to one breaker at a time which is dangerous because of the shared neutral. To make this right, the wires should be on a two pole breaker or use a breaker handle tie to make sure it is on two different legs and able to cut power to both. I’ve indicated where the wires come in and the neutral wire with circles. The arrows show which breakers.
I do not know why some of my photos are showing up sideways. I rotated them before I uploaded them.
Yes, the two circuits of the MWBC sharing a single neutral need to be on different “phases” otherwise the current become additive in the neutral conductor. This is a common error for DIY’ers.
The simultaneous disconnect requirement has only been around for a few code cycles so on older installations it was not required.
Thanks Robert, so technically the 40 amp current can be on the neutral.
Yes when you have two 20 amp circuits.
The 40 amp current IS on the neutral, not “can be”.
I think** Can be** is correct .
The only way 40 amps IS if there was 20 amps on each hot wire not likely to happen .
Yes, the neutral current will be anywhere from 0 to 40 amps depending on the phase current, that’s why these wiring errors may be there for years or decades without any problems.
Oh yes, I stand corrected.
That would be if both breakers were drawing 20 amps each
This is correct. The potential for 40 amps on the neutral is possible under the correct conditions, but not always present.
Yes, I meant potentially, or up to 40 amps on the neutral.
If you have a clamp meter and both circuits are in use, you can validate whether the grounded conductor is carrying the combined amperage or differential, but you don’t need to, you nailed the issue.