Last night I dozed off on the sofa and was awakened by a cracking noise which I quickly traced to a plug on the wall which was clearly sparking inside the case. Alarmed, I unplugged it, turned it off and checked the trip switches but nothing else seemed untoward.
The plug in question runs to a four-socket extension. Plugged into the four sockets were a TV soundbar, two games consoles (and Xbox 360 and a PS4) and some incandescent Christmas tree lights, none of which were actively drawing power at the time this happened.
Today, presuming the extension to be at fault, I went out and got a new one with surge protection. I plugged the Christmas tree lights in first, and it seemed fine. Then I plugged in the PS4 and – without turning the console on – the surge protection tripped and the lights went out. Puzzled, I repeated this and got the same result.
I then plugged in the lights, Xbox and soundbar and everything seemed fine. Then I added the PS4 and there was no effect. I tried turning the Xbox on and the tree lights briefly went out, then returned. I turned that off and turned the PS4 on: no effect.
I cannot recall whether I'd ever seen this happen before: I have a vague memory of this extension sparking briefly once or twice when power was drawn. But this was prolonged sparking, enough to wake me from sleep. Also I have never had issues plugging in the PS4 before, but we don't normally run Christmas tree lights from this extension.
What's going on here? Should I be worried, or is the surge protection enough to keep me safe? Do I need to swap things around or unplug things when not in use?
Best Answer
You have a series arcing fault inside the receptacle. There is a gap in the conductors somewhere just large enough to make electricity leap across the gap. You know that because you saw it arc.
Left alone it can burn your house down. The arcing makes a lot of heat, and then it's a race between whether the arcing will erode enough material to widen the gap enough to arrest the arcing, or make enough heat to set something on fire inside the walls. Hard to fight a fire inside walls.
This type of problem is common, and it's caused either by the cheap 50 cent tier receptacles losing their grip strength or cracking, or "backstab" wire connections where a wire is jabbed into a hole and grabbed by a spring. The backstab only touches at a couple points, not a long edge the way screw connections attach.
The arc is in series with loads you plug into this receptacle, or possibly ones downline in the circuit. Removing the loads should stop the arcing for now, but this needs to be fixed.
The cure is to replace the receptacle. This is handyman work not even electrician work, and shouldn't need a permit. A handyman should watch for "tabs" on the side of the receptacle to make sure they are not broken off, as they need to be in some comfigurations. And should use the side screws, not troublesome backstabs. If you attempt it yourself, turn off the breaker first, use the better $3-tier receptacles, shoot pix of the "as-found" wiring before and check the wires for arc damage, more to conclusively determine the source. Don't hesitate to ask us if you get stuck.
Your "trip" didn't detect it because trips only look for one kind of failure: overload. This arc fault couldn't flow any more current than the appliances normally take. If you want a circuit breaker that also looks for that problem, get an AFCI ("Combination" Arc Fault Circuit Interruptor), which literally listens for arcish sounds. "Combination" means both series faults (which you've met) and parallel arc faults (where the wires short together, but do not flow enough current to trip the overload breaker). If you want one that also protects humans from electric shock, get a dual-mode AFCI/GFCI. GFCI, or Ground fault Circuit Interruptor, looks for wayward current that could zap someone. It is called RCD in Europe.