Faultfinding #6

[Paul.M]

HT I've pm-ed you my answer. Am I correct?

 

[High Tower]

Yup!!!

 

[Paul.M]

I've come across the same problem HT.

After you have given the answer I post up on this thread another example of this fault which will be useful to everyone, almost caught me out once but never again.

 

[High Tower]

Ok so as I said guys don't let your mind over complicate your fault finding process, you always need to be methodical and start with the obvious.

The fault was reverse polarity on the supply tails, by switching the mcb off what I was actually doing was switching the neutral.

Easily diagnosed with a voltage meter

L-n gives supply voltage, but
L-cpc gives 0v, this could also be presented with a disconnected or incomplete cpc so to confirm reverse polarity ....
N-cpc will give supply voltage.

 

[Paul.M]

That is what I came across, reverse polarity but at the meter. The meter had been moved by another electrician and messed up the tails. Since then I always have a quick look at the meter, Henley block and the incoming tails in the cu to make sure. As you say HT it will be switching the neutral at the mcb therefore the line conductor is always live at the fitting.