Shock from neutral when changing light fitting - why?

[colinj]

Hi All, I was changing a light fitting (something I've done many times before). Since it was a switched live to the ceiling fitting I had left the circuit still live (I know but no comments about that please!). Touched the neutral and got a small shock. So used a test screwdriver to see if the neutral was 'live' - it did show live for a few seconds and while I was doing that test another light on the same lighting circuit was flickering. However, after a few seconds the neutral no longer showed 'live'. Many of our light bulbs are LED (some 2 way and 3 way) and I did have an interesting capacitance related problem on another lighting circuit which was solved by using a different LED. Any suggestions please?

 

[James]

simple, the circuit you were working on was not isolated, therefore a shock is likely if you come into contact with a live cable.
N can become live if it is poorly connected or disconnected from the neutrual terminal of the supply.

Always ensure you have tested a circuit and proved it is dead before working on it.
shortcuts can be fatal.

 

[colinj]

simple, the circuit you were working on was not isolated, therefore a shock is likely if you come into contact with a live cable.
N can become live if it is poorly connected or disconnected from the neutrual terminal of the supply.

Always ensure you have tested a circuit and proved it is dead before working on it.
shortcuts can be fatal.

Hi James - thanks for your answer. I understand that might occur if there was a permanent fault. This seemed to 'discharge' from being live merely by me touching with a test-screwdriver such that a few seconds later was no longer 'live'. Hence my thoughts about some sort of capacitance discharge? I should have said that this is my house that I have lived in for 30 years so I am very comfortable with the wiring being OK. It has had several modifications over the years, all done by qualified professionals and certified so I don't think that there is a permanent wiring fault causing this.

 

[James]

If you get a shock from a neutral conductor, there is a fault somewhere

N should be tied down to earth potential

 

[Darkwood]

I would suggest you broke the neutral circuit when changing the fitting, was there more than 1 neutral? If so this could raise the potential of one of the neutrals to 230v, you are lucky you are able to post a query as it can kill you just like the live wire can, this is why you should fully isolate the power regardless, with all respect to DiY status we always say a little knowledge can be dangerous and you nearly learnt that the hard way, other causes are faults and borrowed neutrals all would have likely been isolated if you switched off your power.

 

[colinj]

I would suggest you broke the neutral circuit when changing the fitting, was there more than 1 neutral? If so this could raise the potential of one of the neutrals to 230v, you are lucky you are able to post a query as it can kill you just like the live wire can, this is why you should fully isolate the power regardless, with all respect to DiY status we always say a little knowledge can be dangerous and you nearly learnt that the hard way, other causes are faults and borrowed neutrals all would have likely been isolated if you switched of your power.

Good point - i think you've solved it. There was more than one neutral - though they were twisted together. It is possible that they were loose enough not to make a good contact, so me or the screwdriver touching them completed the circuit - until they had slipped back into good contact and no longer tested live? Lesson learned - a little bit knowledge has just increased and I will be more careful in the future - thank you!