When we bought the house one room had a light switch with a 'on at dusk off after X hours feature'. Something was wrong with this (working intermittently), so I replaced it with a normal light switch.
There are four MCBs marked lights and it was not clear which was the relevant one. So I switched all of them off and tested for dead with a multimeter.
Having replaced the switch with an ordinary but old one that we had, and the switch was working correctly, I wanted to determine which was the correct MCB. So I left the switch hanging off the wall, turned on the MCBs one at a time and after each one I used the multimeter to test for live.
In every case the meter showed no voltage. I know the meter is okay as I checked it on a socket and it showed c. 240V.
When I was testing for live I was connecting to the screws that hold the wires in. It is an old light switch and these screws have a lot of patina on them (they are very dull / dirty looking). So I wonder if this patina was acting as an insulator.
Does that sound plausible?
If so then (and this has only just occurred to me) I could replace those screws with ones from the switch that I removed. Those are chromed and so should be okay.
NB I subsequently realised that I could work out which was the correct MCB, by switching the light on and turning the MCBs off one at a time.
There are four MCBs marked lights and it was not clear which was the relevant one. So I switched all of them off and tested for dead with a multimeter.
Having replaced the switch with an ordinary but old one that we had, and the switch was working correctly, I wanted to determine which was the correct MCB. So I left the switch hanging off the wall, turned on the MCBs one at a time and after each one I used the multimeter to test for live.
In every case the meter showed no voltage. I know the meter is okay as I checked it on a socket and it showed c. 240V.
When I was testing for live I was connecting to the screws that hold the wires in. It is an old light switch and these screws have a lot of patina on them (they are very dull / dirty looking). So I wonder if this patina was acting as an insulator.
Does that sound plausible?
If so then (and this has only just occurred to me) I could replace those screws with ones from the switch that I removed. Those are chromed and so should be okay.
NB I subsequently realised that I could work out which was the correct MCB, by switching the light on and turning the MCBs off one at a time.
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