[Karl Hungus]

On a 20 amp circuit breaker, my basement bathroom has a switch that controls 2 lights, 2 unswitched outlets, and a group of 3 switches to control the lights/fan in shower.

I'll describe it as simply as I can. It seemed straightforward to me to bring 12/2 to the first box which houses the first switch and use pigtails to the switch and a 12/3 wire from there. The 12/3 connects to the first light's box, then the first outlet which is on the wall, then the second light and then bring 12/2 to the final outlet (GFI) next to the sink, which shares a box with the switches to the lights/fan in the shower. With the 12/3 I was able to use the red wire to switch the 2 lights and maintain power with the black to the first outlet.

This set-up worked for the most part without the GFI on the wall. However, the inspector noted that I had the GFI over the sink, but wanted me to put one in on the wall too, as it isn't downstream from the one over the sink. When I try to do this, the GFI keeps tripping every time I switch the light on. I connected the black directly to the line in on the GFI, the corresponding neutral to line in. The load black/neutral connect directly. The red wires tie together. With the switch off, it works. Or if I take the light off altogether, cap the ends and hit the switch it works without tripping the GFI.

Is it because the red/black are sharing a neutral? If this is the problem, is there a solution?

One other thing, I have gone through 2 dimmer switches in a year-and-a-half. They stop having the ability to dim, but still work as a switch. Not sure if this is evidence of another problem or cheap dimmers.

Thanks in advance.

[tkrussell]

I sketched out as you describe the circuit, if I follow it correctly, the white wire between the first GFI and the second light is a shared neutral, and this will always trip a GFI.

Change the first GFI to Line only, and use a GFI with Line only at the last outlet.

[Karl Hungus]

Thanks. That worked. At least it isn't popping when I hit the switch. I assumed I had to have something run out of the load side.