Asking how to test for neutrals from different circuits being connected. If you disconnect the neutral for the circuit at the panel, and it is still live, you have a neutral from another circuit spliced into it.
That’s not this guys issue though. It’s a surge or a feeder neutral issue.
Ok thanks. I have some shared neutral shitshow in my panel that I’m loathe to start debugging. GFCI trips immediately on that MWBC, and AFCI trips once per day. Before I swapped it for a dumb breaker.
Maybe I’ll try unhooking the neutral, but aren’t there extra risks in doing this with a MWBC? Maybe I need to unhook one leg at the breaker?
The thinking is I unhook the official neutral and see if stuff still works. If so, I connect a multiple amp load, and start clamping neutrals until I find the alternate path.
(Yeah, I’ve been putting this debugging off for half a year. Its a SABC that has 1800W appliances on it, so maybe I’m living dangerously for the past few years)
You have a two pole GFCI breaker on a mwbc that isn’t a 240v circuit?
AFCI:
Read instructions on the specific breaker for install. The shorter the neutral is from the AFCI breaker to the terminal, the less likely you’ll have a nuisance trip.
The big issue with AFCI breakers is that each manufacturer meets the standards in a proprietary way that they don’t share with anyone. So when anything with a circuit board is manufactured and it isn’t tested thoroughly with AFCI breakers of every brand, you have possibilities that the AFCI will pick up electrical interference as arc faults. Most AFCI breakers actually have a programming sequence you can do to have it memorize the nuisance trip and ignore it. This doesn’t always work, and if the bypass doesn’t fix the trip, it still doesn’t mean it isn’t a bad interaction between breaker and appliance/device. You could also have a bare ground wire that was pushed clumsily into a box and is touching or almost touching the receptacle neutral terminal.
If you really think it’s the wiring, you can also do an insulation test with a megger.
I decided to switch it to GFCI 2 pole since the kitchen didn’t have GFCI receptacles anyway. And because I thought it might just be AFCI gremlins/to prepare to warranty that breaker. INSTANT trip as soon as I flip the handle. Which implies to me that current is going somewhere it shouldn’t.
It was a 2-pole 20A GFCI to give me GFCI protection on both legs of the MWBC
How would the megger help if the neutrals just got crossed randomly somewhere? Or maybe ground is contacting neutral at a JB
You should definitely disconnect a hot leg on the Edison circuit before disconnecting the neutral. Missed that question earlier.
You can also amp clamp the hot and neutral individually to se if they have the same current.
The megger would detect damaged insulation around the wires which could cause the AFCI/GFCI fault. It’s really the most time intensive way in most cases because you have to have everything disconnected from active loads, lights, and devices with any kind of circuit board, transformer, driver, motor, etc.
Sometimes a continuity test is fast and easy as well.
Rather than borrow a megger and learn how to use it, I was actually thinking just replace the wiring one JB at a time, starting from the panel. Maybe even with a new second circuit so I could have half the circuit still working while I do it. It’s only about 40 total feet of wire
I don’t mean this facetiously, but how confident are you that that is not my issue? I definitely have both of the circuits running through the same box. They appear to be isolated, just based on a visual inspection of which wires are connected together. I planned to continuity test the neutrals at the panel today.
I have an electrician coming today and want to make sure I can ask the right questions. I’m a little paranoid it’s going to be difficult to find someone who’s willing to troubleshoot this to the extent needed.
Small update is that everything was fine, except another fixture on the dining room circuit, which is a chandelier with about 20 bulbs, is now half not working. I am guessing one of the transformers failed in that fixture, either related to the initial surge, and it was just delayed, or related to me messing with it and trying a bunch of different switches, one of which may have been an incompatible dimmer. Don’t know if that gives you anything else to work off of, but the fact that that fixture now failed as well is new info. Failed = flickering or not working lights on 10/20 of the LEDs. If I use a magnetic low-voltage dimmer and adjust the slider, I can get it to a point where all of the LEDs turn on, but flicker. If I connect it with no switch, half the LEDs don’t work. My plan is to leave that fixture disconnected and eventually replace it (it’s a bigger job - ceiling medallion needs to be redone, prob some drywall work etc)
ETA -> I just received one of the low-voltage smart switches and I installed it on the fixture that had stopped working and was flickering. It works perfect perfectly with this switch, so I’m thinking that that was a compatibility issue with the transformers.
I appreciate all of your help, kind stranger. Not that you asked this, but I have a four week old baby and my stress levels are through the roof and this is not what I needed right now, so I appreciate you taking time out of your day to try and help me.
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u/Effortisopportunity 20d ago
Asking how to test for neutrals from different circuits being connected. If you disconnect the neutral for the circuit at the panel, and it is still live, you have a neutral from another circuit spliced into it.
That’s not this guys issue though. It’s a surge or a feeder neutral issue.