Two breakers, one neutral bundle

I’ve read through the threads and not sure if I’ve found anyone with this specific situation…

I’ve connected up more than 20 GE smart toggle switches with no problem, until yesterday. Here is the problem I am running into…

I am connecting a ceiling light that is on a 3-way. The master is in a 3-gang box. The other two switches (one is a standard “dumb” and the other is a GE smart toggle controlling a corner light) are on one circuit. The ceiling light is on a separate breaker, and the slave is in a 5-gang box across the room.

The problem is that there is only one bundle of neutrals in the box - it appears to be a total of 4 white, one coming out with each of the 3 switches, and one coming from the bundle of copper/ground. This is relatively new construction in North Carolina - less than 18 months old.

No issues with the corner light, but (surprise) connecting the splice from the toggle controlling the ceiling light to the neutral bundle immediately trips the breaker, but does not trip the other breaker which controls the “dumb” switch and the corner light controlled by the smart switch.

I’m 99.99% sure the line, load, and traveler are wired correctly, as is the slave switch.

There were no issues with the shared neutrals prior to swapping out for the two smart switches, so I’m pretty sure that’s the issue (and understand why with GFCI on that circuit could cause it to trip).

I’m not an electrical novice, but neither am I a licensed electrician. My question is, is there any way of unbundling the existing neutral wires to connect properly, or will a new neutral need to be pulled? Or any other suggestions?

I’ve checked and in other gang boxes I do have some with more than one circuit and only one neutral, but in every other situation where I’ve had to connect to a shared neutral, it’s been with only an add-on switch, so this is the first instance that I’ve had two master/standalone switches in the same box attempting to connect to a single bundle of neutral wires.

is there a neutral bundle available in the other switch box? sounds like you should switch your master and aux swtich

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There are two neutral bundles in the 5-gang box, yes, and the add on is also connected to neutral. As I understand it, both master and add on have to be connected to neutral.

yes they do. But you can connect them both to the same neutral.

Ok. I will try this. In which case if I am switching, the hot in box one (current master) should then be pigtailed with the wire that is currently in load (black), red traveler remains same, white neutral remains same?

Then in box 2, remove pigtail between existing load (from 1) and red load on that box, connect black to line, connect previously pigtailed red to load, and other red traveler remains same?

tough to say without some pictures or wiring diagram. Which diagram from this site fits?

I’ll take a look and report back. Thanks!

Pretty sure it is option 1.

Just to close the loop on this… I did exactly what was outlined above (essentially bypassed Box 1 altogether and made it the add-on switch) and, aside from first realizing the neutrals from two different breakers in box 2 were switched around and fixing those, all is now working properly.