So I am trying to set up a GE 12725 and 12732 (fan speed control and dimmer) for the ceiling fan in my bedroom. I have them wired to fan properly but there is no neutral on that circuit at the switch location. There is however another neutral from another circuit there as well as a hot. They are on the circuit for the receptacles around the room. I assume they are there so one could have a table lamp on the switch if desired. Anyway, if I connect one or the other smart switch to that neutral alone, it works fine. If I connect them both, the breaker trips on the fan circuit AND the receptacle circuit.
Does anyone have any idea why this might be? Any idea on a remedy? Do I need to move one of the smart devices to the fan box?
This called a shared neutral, those circuits are being different phases. This could be a potential hazardous situation. see this https://www.youtube.com/watch?v=IBcw2JJsELs . One easy solution is to go to the breaker and put both circuits on the same breaker.
This circuit is coming from a different breaker.
Do not mix them.
Two ways to fix: 1. Rewire (preferred) and 2. Used an in-wall relay at the light.
It is not. Would be if 2 circuits would have a common neutral (basically illegal). In this case there is only one Line+Neutral circuit. The first one only has power from the light to the switch and then back to light.
I don’t think you wired them correctly. There are two possibilities that caused both breakers to tripped.
The circuit is overloading because of too many loads on it.
Your smart switches is not wired correctly and caused a short circuit when both connected. Mind drawing out your old wiring configuration and how your wired your smart switches with the borrow neutral?
Borrow a neutral from another circuit is not a good idea especially if both lines are on the same phase. If they are not on the same phase then you need both breakers tie together with a handle tie. It’s a clip to trip both breakers if one tripped. Possibly your local state allows this but you have to check.
I know the switches are wired to the fan correctly as I can get them to work one at a time with the borrowed neutral. However, it sounds like the consensus here is that using that borrowed neutral is a bad idea. I will disconnect that and probably have to run the neutral from the fan box down to the switches. I don’t think there is enough room in the fan box or fan housing for the switches.