I had an extension socket hanging off a switched wall socket. I turned off the switch and was manipulating the wires in the extension. In the process I managed to trip the circuit breaker. I am pretty sure the wires were not live, although not sure. Is it possible to trip the circuit breaker shorting neutral to earth, assuming the wall socket is single pole switched that did not isolate the neutral wire? I have not checked to see if the wall socket is correctly wired because it's in a hard to access place.
Shorting neutral to earth
- Thread starter DiyNutJob
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Neutral to Earth faults or touching will trip a RCB/RCBO - is that what you have - maybe photos would help , including the breakers that tripped
The circuit breaker is the typical domestic thing-box with fuses and flip switches near the electric meter. I did grab all 3 wires to feed them out of a blanking box. All 3 wires touched. I am just wondering if it is normal for that to trip the breaker? It took out power for other people in the house using devices.
As ETAF said, if you have an RCD or RCBO in the consumer unit it will trip if either the live or neutral touch the earth. If, for example you live in a two story house and it knocked out the sockets both upstairs and downstairs then I think you are on a split unit. The upper and lower crcuits might be on separate "fuses" (MCBs) but in the event of a earth leakage problem, all of the MCBs will be rendered in operable until the RCD is flicked up. The RCB deals with earth problems, the MCBs deal with too much current (that is may lay explanation- I am not an electrician)
I would expect the RCD to be double width and have a test button on it.
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Thanks. Whatever it is, it's working
I was a little surprised by the trip since I have switched it off.On a related note, for a switched, fused spur, is there still risk of a trip after switching off and taking the fuse out? Of course, I am talking about manipulating the output side of the spur.
Thanks. Whatever it is, it's working
On a related note, for a switched, fused spur, is there still risk of a trip after switching off and taking the fuse out? Of course, I am talking about manipulating the output side of the spur.
If the fused spur is only isolating the live, then yes, if the neutral after the spur hits the earth, it will trip.
I am only a lowly decorator but when loosening off face plates, I have tripped loads of RCDs even though I had already flicked the Mini Circuit Breaker (MCB) in the consumer unit. Sometimes the earth or other cables pop out when you loosen the metal socket plate for painting.
This is getting confusing.
The point is when you turn off the circuit breaker (MCB - Miniature Circuit Breaker) for just one circuit, it only disconnects the Line(live) wire and not the Neutral, so when you touch Neutral to Earth some of the current being used on the other circuits flows through the Neutral and through the Earth wire to Earth, consequently tripping the RCCB (double width Residual Current Circuit Breaker) which covers several circuits and is doing its job.
An RCBO (Residual Current Circuit Breaker with Over-current protection) is a combined MCB (Miniature Circuit Breaker {over-current}) and RCD (Residual Current Device) covering just one circuit.
The point is when you turn off the circuit breaker (MCB - Miniature Circuit Breaker) for just one circuit, it only disconnects the Line(live) wire and not the Neutral, so when you touch Neutral to Earth some of the current being used on the other circuits flows through the Neutral and through the Earth wire to Earth, consequently tripping the RCCB (double width Residual Current Circuit Breaker) which covers several circuits and is doing its job.
An RCBO (Residual Current Circuit Breaker with Over-current protection) is a combined MCB (Miniature Circuit Breaker {over-current}) and RCD (Residual Current Device) covering just one circuit.
No, the Switched Fused Connector Unit (FCU); the cable is the spur; has double-pole switching and switches off the Neutral as well. Taking out the fuse does not affect this.
That makes sense, and I have checked and see that there is possibility of a single pole switched, fused, spur. So, there's no short cut to turning off the entire circuit.
There's nothing lowly about being a decorator. If you know stuff, you are pro.
I am shaken by my experience with with the extension lead. Although there was no life risk. I always wear rubber gloves and rubber sandals when working with the electrics. The FCU is DP guaranteed 100%? Was this the case 30 years ago? The house I am playing with is built around then.
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It might not be the case with very old ones.
Ok, feck it, I'll turn off the whole circuit.
Always best, but not that important. Just take care not to touch the wires together.
If the FCU is DP then the Neutral will also have separate IN and OUT for the Neutral wires; if not both in same terminal.
A few years ago I was working at a mate's house. He didn't want to pay what the local electricity provider was paying to move the consumer unit from the back of the house to the front of the house. He found someone else that was cheaper (and accordingly illegal). The guy who moved the meter was telling me that he used to work for the company until they discovered that he was moonlighting and illegally moving meters for cash. Once he cut through the exterior braiding, he put on rubber gloves to trim the insulation on the live and neutral. I asked him how he could be sure that the gloves were safe to use. He said that as they approach the "end of life" he experiences a slight tingling. I then asked him what would happen if the two cables hit each other- would he plunge the whole neighbourhood in to darkness? He replied that if they are far enough away from the "box" in the street, the two cables would just keep making banging noises until separated.
(I took what he said at face value).
It goes without saying that I stayed on the other side of the room whilst he was working.
I have to admit that from time to time I have used insulated pliers and screw drivers to push live cables back in to sockets. It is not something that I would recommend though. AFAIK, you can only die once, but, by definition, it is pretty terminal.
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