About a year ago, I installed a secondary breaker panel in my detached barn. It is a very simple set up. I added a 50 amp single pole breaker on my main panel in the house, ran #4 wiring in conduit out to my barn. There I installed a sub panel with 3 breakers in it.
In the sub panel, the Black supply wire energizes the circuit rails, the white supply wire is connected to the Neutral bar and ground wire to grounding bar in panel. Breakers each have a single wire connected to each for 3 separate and very simple runs. One breaker controls a line of 3 outlets in the barn. The second breaker controls overhead lighting in the barn with one switch location. The third breaker is connected to a wire that is in conduit and goes underground to two smaller sheds to provide a light in each and an outlet in each.
These are all independent of each other, all done with new wire and have worked flawlessly for about a year now. The other day we had a very rainy day. I noticed that the barn lights were on, went in to check and confirmed that the light switch was off. This was obviously not right. I am not sure if the lights were fully illuminated or just partially, but they were on. I turned off the breaker controlling the lights and they were still on. Only when I shut the breaker going out to the sheds did the barn lights go off.
Somehow, the circuit controlling the shed lights and outlets is energizing the barn lights even with the breaker for the barn lights off and the switch off. I have rechecked my sub panel wiring and have confirmed that each circuit is wired properly and there is no visible way that those two separate lines should be energizing each other.
Somehow, power from one circuit is finding its way into a separate circuit and energizing the lights even with the breaker and switch turned off for that circuit. As I stated before, this system has worked flawlessly for about a year and this issue seems to come out of thin air. What did I do wrong?
