[Bill Verburg]

Originally Posted by mikehinton

About 7 years ago, I installed a new wiring system for my shop, barn, and a couple of other outbuildings. All 4 of the circuits are serviced by a sub-panel, which was installed by our electrician. I did all of the other wiring myself (I've done similar projects several times over the last 20+ years). The circuits are all very simple - just a bunch of outlets with a few switched outlets for fluorescent lighting. There are no 3-way switches anywhere.

Everything worked fine upon installation, and continued to work fine until a couple of weeks ago. I went out to the barn to plug in a battery charger, and no power. Went to the box and found that the circuit breaker had tripped. That seemed odd, but I just reset it and continued on. A couple of days later, I went to turn on overhead lights, and same circuit was tripped. Strange. Reset it and continued. Last week, I encountered the same thing. This time, when I reset the circuit, I heard a "pop" coming from the barn, and the breaker tripped again. As far as I can tell, there was no load on the circuit when the breaker tripped.

So, I'm figuring that there must be a short somewhere in that circuit. A couple of questions: 1. Why would a short suddenly manifest itself after 7+ years? 2. Is there a way to track down the source without disconnecting everything? The "pop" I heard was coming from a junction box in the barn. When I removed the cover, the large wire nut (joining 6 neutral wires) was burnt to a crisp.

Any advice appreciated! Thanks for reading!

Mike

Is any of the wire separate tnn wire in conduit? I had a similar occurrence after 10 yrs in service except the breakers and GFI didn't trip, there was just no power in one leg. The wire had apparently been nicked when pulled and it took all those years of arcing to ground to finally erode the wire to the point that it would no longer conduct. The funny thing was that per code all the conduit was plastic except where the nick was, under a paved drive. At that point code called for metal conduit which facilitated the arc.