I've successfully fitted a dimmer switch.
I've used a small voltage test pen to "direct test" the face plate screws on other light switches - I've noticed that some of the screws return a direct test result of between 12 and 36v.
I assume - maybe stupidly - that this is because they are part of an earth circuit.
Why is it though that some screws do not return a reading?
some boxes are made of plastic, especially those intended for fitting into plasterboard walls.
Are you sure thee ones which dont return a reading ar actually connected to earth though. Brian
Is this a proper tester, ie where you need to have a return, or are you in fact just reading a very high impedence induced voltage using yourself as the return, in which case maybe its you who is charged and the screws making the eearth return.
Brian
In article , charles scribeth thus
Sometimes the "earth" on lighting circuits isn't connected too well and the faceplate screws are "floating" above Earth potential thats to say there're picking up a small voltage via Capactive and inductive effects via leakage in the wiring.
You'll find that this will disappear if they are correctly earthed..
Was there an earth wire inside the switch backing box and was it connected? Older wiring may not have any earth on the lighting circuits. So you must only use plastic light switches and dimmers with that. And correctly, the screws should only be plastic - or if metal have a plastic cover.
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