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scubar
06-19-2009, 04:27 PM
I've removed a Lutron dimmer switch with the goal of installing a regular light switch. There are two romex sets of wires coming into the box. One set reads a normal 118VAC between black and white. But the other set reads nothing between the black and white wires but on that set, there is 118 VAC between the black wire and ground AND between the white wire and ground.

Why do the readings on the second romex set make sense? Where would they be getting power from? The power goes away from all of the wires when the breaker is opened.

Appreciate your explaination on these readings.

Ron

Thatguy
06-19-2009, 07:00 PM
But the other set reads nothing between the black and white wires but on that set, there is 118 VAC between the black wire and ground AND between the white wire and ground.

The black and white are connected together (maybe by an incand. lamp filament)?

drick
06-19-2009, 08:23 PM
Why do the readings on the second romex set make sense?

Who said they did? Cheap digital DMMs are notorious for picking up stray voltages.



Where would they be getting power from?

Its induced voltage it picks up off other wires it runs next to in the ceiling/ wall/etc.



The power goes away from all of the wires when the breaker is opened.

Because you shut off the wire inducing the voltage.

Ok now before you go blowing your fingers off check if I'm right. Connect a test light between the ground and the white wire in the second set. Did it light up? If yes then I'm wrong and something else is going on. Otherwise its safe to say that the first pair is power and the second pair is from the fixture. Connect the whites from each pair together and wire the switch between the blacks.

rick

Thatguy
06-20-2009, 05:47 AM
An incand. test light; no neons.
http://en.wikipedia.org/wiki/Phantom_voltage

scubar
06-22-2009, 04:12 AM
Thanks for your responses. The switch works fine and the voltage was likely feed through another lamp.

Ron