Baffled - Cutting wire tripped fuse board

OlyBobs · 7 Apr 2013

Hi there,

Does anyone have any thoughts of what might have occured in this situation.

I have a power outlet in my bathroom cupboard which mysteriously stopped working around the time we merged two seperate flats in our property together into one. It's tough to know what specifically might have led to this happening but we've been ok to concede that this supply is now redundant.

Im currently doing some work in this bathroom cupboard and keen to get this supply either up and running again or safely capped off somehow. We tested the wires in the power outlet and sure enough they seemed to be dead. We tied the live and neutral together, thinking this would be an idea to ensure the fuse board would trip should the power come back to this wire.

Anyway, yesterday I decided I would cut the wire close to where it enters the floor, so I could wire it into a blank outlet box and label it as being redundant. Weird thing is when I cut the wire, the lights went as the fuse switch to our whole first floor tripped. I cant figure out how a wire which has not worked for 2 years and when tested shows no sign of life but when cut has tripped the fuse board. Any thoughts?

ricicle · 7 Apr 2013

//www.diynot.com/wiki/electric...ergised_circuits_with_neutral_to_earth_faults

sparkwright · 7 Apr 2013

Was it an RCD (or RCCB) or MCB that tripped?

If the live wire was disconnected, and the neutral and earth was connected, cutting the cable could trip the RCD if there is one.

If this is the case, it seems the live has been disconnected, or perhaps the live is connected to the light, meaning the shaver only works when the light is on????

WabbitPoo · 7 Apr 2013

OlyBobs said:
Hi there,

Any thoughts?

Yes, you don't know what you are are doing and are a danger to yourself and others.

Linking a live and neutral in the hope that it'll "trip the fuse board" in the future seems to me to be highly risky (not that I am an electrician, but I do know my own limitations).

Just my 2p and I hope it helps (keep you alive)

ban-all-sheds · 7 Apr 2013

OlyBobs said:
Hi there,

Does anyone have any thoughts of what might have occured in this situation.

Yes - it all goes back to this time:

I have a power outlet in my bathroom cupboard which mysteriously stopped working around the time we merged two seperate flats in our property together into one.

when you allowed an ignorant buffoon to do electrical work in your property.

It's tough to know what specifically might have led to this happening

Incompetence.

OlyBobs · 7 Apr 2013

Wow, some jumping to conclusions going on there

The person who worked on the merging of the electricity of the flats was a highly experienced electrician. And I should point out my comment that it is tough to know how the supply stopped working relates to the fact that there had been a large amount of work taking place in our property. Ie. we dont know what day this occurred and what work may have triggered it. How anyone can assume the electrician was incompetent I don't know.

Yes I understand linking live and neutral together is not safe. Again some jumping to conclusions though, this was done at one point during supervised testing and was not intended to be any kind of solution, I agree that would be stupid

Really appreciate the help from those who have pointed out ideas on what is going on, and ill try to be clearer next time in my post. Cheers

ban-all-sheds · 7 Apr 2013

OlyBobs said:
How anyone can assume the electrician was incompetent I don't know.

Because he left a socket which was not only not working but he didn't know why it wasn't working.

Yes I understand linking live and neutral together is not safe. Again some jumping to conclusions though, this was done at one point during supervised testing and was not intended to be any kind of solution, I agree that would be stupid

Actually connecting all unused conductors together and to earth is recommended.

mikhailfaradayski · 7 Apr 2013

OlyBobs said:
....../snip/...... supervised testing

That sounds interesting.

Just out of curiosity, can you expand on that bit please.

Scoby_Beasley · 8 Apr 2013

OlyBobs said:
Wow, some jumping to conclusions going on there.

Not really. I'm not having a dig but when the re-wire/alterations were made the electrician should have found where that outlet was supplied from. If it was to be made redundant, all conductors should have been connected together so at any time in the future it would be obvious (maybe not) to the next electrician/person that this is a dead cable.

That is at both ends.

As has been said, by cutting the cable you made a momentary connection between neutral and earth and tripped the RCD.

OlyBobs · 9 Apr 2013

Ok thanks for all the replies, I do understand the POV regarding the electrician, the thing which i maybe wasn't clear about was that this supply was found to not be working a good week or two after the electrician had done his work. Floorboards had been re-installed and a lot of work completed, hence my comment that we were happy to concede this supply was dead.

Ive never been very comfortable about this odd cable though, hence my plan wire it into a (labelled) blank box. What I should have done before cutting the wire is turn off the power first so that has been a learning point for me to leave it to the experts. I was quite surprised that a seemingly dead cable could trip the RCD. But on the plus side at least it now has given us a clue as to the situation, we can now chat to an electrician and see about getting it resolved one way or another

Thanks again

gaspro1981 · 10 Apr 2013

ban-all-sheds said:
OlyBobs said:

How anyone can assume the electrician was incompetent I don't know.

Click to expand...

Because he left a socket which was not only not working but he didn't know why it wasn't working.

Yes I understand linking live and neutral together is not safe. Again some jumping to conclusions though, this was done at one point during supervised testing and was not intended to be any kind of solution, I agree that would be stupid

Click to expand...

Actually connecting all unused conductors together and to earth is recommended.

Sorry to have to ask but why is this ??

flameport · 10 Apr 2013

Unused conductors are connected to earth as if left unconnected, voltages can appear on them due to capacitance or inductance.

It also ensures that if one of them was mistakenly connected to a live conductor, or someone put a nail through the cable etc., the fuse or circuit breaker would operate and disconnect the supply.

gaspro1981 · 10 Apr 2013

flameport said:
Unused conductors are connected to earth as if left unconnected, voltages can appear on them due to capacitance or inductance.

It also ensures that if one of them was mistakenly connected to a live conductor, or someone put a nail through the cable etc., the fuse or circuit breaker would operate and disconnect the supply.

Cheers muckka, makes sense ta

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Baffled - Cutting wire tripped fuse board

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