RCD trips a few minutes after lights turned on

[harpoon]

A multimeter ...

 

[harpoon]

In the end, it was a L-E fault ... One of the lights had too much insulation around it causing the wiring insulation to become brittle and eventually short.

All is good now ...

 

[harpoon]

Congrats to Murdoch and Ian for their educated guess ... We should have a competition on here for fault finding ...

 

[Octopus]

Congrats to Murdoch and Ian for their educated guess ... We should have a competition on here for fault finding ...

Thanks for feedback. Who found the issue?

 

[DPG]

In the end, it was a L-E fault ... One of the lights had too much insulation around it causing the wiring insulation to become brittle and eventually short.

All is good now ...

What about the N-E short you said you had found? Did the L-E short not trip the MCB?

 

[harpoon]

We opened up the switch box and eventually the electrician determined that it was not the N-E short. The N-E fault was a false alarm probably triggered by the RCD (not sure about that) ?
The L-E fault was still resistive, low enough to trigger the RCD, but high enough not to draw too much current.
Goes to show that electricians and builders have different mindsets ... I guess the builder was over-keen to put insulation in the ceiling ... and just overdid it. The electrician on the other hand did anticipate this and created enough space around the lights.
In any case, I'll be switching to LEDs from now on ... less heat and power dissipation !

 

[SparkyChick]

The N-E 'fault' is most likely the N-E loop of a TN-C-S installation. If you're not an electrician, with TN-C-S you have a line conductor and a neutral conductor coming in to the service head. The earth is then linked to the neutral conductor. TN-C-S stands for Terra Neutral Combined Separate as in earth/neutral combined (in the cable) and then separate (at the service head).

On the consumer side, if the installation is not fully isolated you will get a continuity reading between earth and neutral which is why you should fully isolate circuits for this kind of fault finding.

 

[harpoon]

Thanks SparkyChick ... I drew the line when I have to open up my consumer unit.
Maybe later in the year (can't believe June is coming to an end !) I will enroll in a course and get qualified as an electrician to better protect my house !

btw, I had the electrician test my RCD again to make sure it is all working and it is.

 

[Octopus]

^^ qualify as a spark won't give you the expertise and experience to fault find imho

 

[harpoon]

agreed ... but it is a start. I am already competent in most things electrical/electronic ... but do not know much about a household (or industrial) installation as well as all the tests that are typically performed. Saw my electrician's Kewtech KT65DL and I was already drooling ... =)

 

[Ian1981]

The N-E 'fault' is most likely the N-E loop of a TN-C-S installation. If you're not an electrician, with TN-C-S you have a line conductor and a neutral conductor coming in to the service head. The earth is then linked to the neutral conductor. TN-C-S stands for Terra Neutral Combined Separate as in earth/neutral combined (in the cable) and then separate (at the service head).

On the consumer side, if the installation is not fully isolated you will get a continuity reading between earth and neutral which is why you should fully isolate circuits for this kind of fault finding.

Will happen on TN-S also as neutral and earth connected at the star point of the transformer

 

[SparkyChick]

Will happen on TN-S also as neutral and earth connected at the star point of the transformer

Very true

 

[Deleted member 9648]

Thanks SparkyChick ... I drew the line when I have to open up my consumer unit.
Maybe later in the year (can't believe June is coming to an end !) I will enroll in a course ,perhaps in November,and by Christmas I'll officially be qualified as an electrician to better protect my house !

btw, I had the electrician test my RCD again to make sure it is all working and it is.

Corrected that for you to be more realistic with current training requirements.

 

[Octopus]

Why would anyone spend up to £6k plus tools to protect their house?

 

[static zap]

Why would anyone spend up to £6k plus tools to protect their house?

Some of need a hobby , away from job ,etc !