LIVE EARTH WHEN REWIRING DOUBLE DIMMER

esalglop · Oct 11, 2023

I have carried out home wiring for 60 years as a competent person, for the last 20 years, I employ a local electrician to check my work and sign it off. My new partner’s dimmer switch failed, the push button would not push, so I purchased a new unit. I turned off the MCB for First Floor Lights and took a photo of the connections. I could not then get the whole circuit back on. When I got the two dimmer switches working correctly all other lights were not powered, however, the earth lead to the other lights was full power.
I had to admit defeat and asked my partner to get her electrician to fix it. He came the following day for twohours, told her their was a fault in one of the other lights (which his employee installed),but it would have been OK for me to have wired all the earths back. I just do not accept this! I hope that she will not now get a massive bill for what I think is maybe an apprentice error?

newfutile · Oct 11, 2023

A loose or disconnected earth or cpc as we call it would not stop other lights from working ,neither should it become live as I assume you mean?
it could possibly appear live due to phantom voltage depending on how you tested this?
if the wiring was an apprentice fault then the lights would not have worked at any point

westward10 · Oct 11, 2023

As above how did you test this earth to say it is live. I would be asking the electrician what this fault actually was.

esalglop · Oct 11, 2023

I wasn’t at my own home so just tested the earth wire with electric screwdriver which showed same bright orange as the brown wires

esalglop · Oct 11, 2023

esalglop said:
I wasn’t at my own home so just tested the earth wire with electric screwdriver which showed same bright orange as the brown wires

westward10 said:
As above how did you test this earth to say it is live. I would be asking the electrician what this fault actually was.

esalglop · Oct 11, 2023

Unfortunately the conversation with her electrician is reported secondhand, he said that the wrong lamps in another dimmer were causing the problem.

westward10 · Oct 11, 2023

How did you test this earth?

Avo Mk8 · Oct 11, 2023

esalglop said:
I wasn’t at my own home so just tested the earth wire with electric screwdriver which showed same bright orange as the brown wires

A neon screwdriver is not a reliable indicator in this situation, as the "ghost" voltage capacitatively coupled from the adjacent live (at least with a disconnected or open circuit cpc) will light the screwdriver. I fear you became convinced the cpc was 'live' by the orange glow, but in reality the voltage would disappear when the cpc was connected, or even if you touched it! (not the recommended method

).
You need a proper low impedance dead tester for doing work like this.

There are many comments on this forum about dangers/ mis-interpretations when using a basic single probe tester.

esalglop · Oct 11, 2023

Thank you for that information. I have never encountered such a problem in my 79 years, although I have lit a flourescent tube by holding it under the low pylon cable so can understand what you are saying.

Avo Mk8 · Oct 11, 2023

esalglop said:
Thank you for that information. I have never encountered such a problem in my 79 years, although I have lit a flourescent tube by holding it under the low pylon cable so can understand what you are saying.

You've got 4 years on me!
My childhood bedroom had a 15A socket (as below) on the skirting board, with the socket part horizontal at the top, and I would stand my neon tester screwdriver in the live socket and watch it from my bed glowing in the dark! (the leak to atmosphere from the top cap being enough to illuminate it).
I don't know who it was gave me a neon screwdriver while I was still at primary school, but it taught me well

[ElectriciansForums.net] LIVE EARTH WHEN REWIRING DOUBLE DIMMER

davesparks · Oct 11, 2023

esalglop said:
I have never encountered such a problem in my 79 years,

Then you've been lucky.
I've encountered it many times in my 20 years of doing this professionally and I'm sure the 100's of years of combined experience on this forum has seen it a heck of a lot.