Hey guys... while helping a fellow apprentice I encountered what I believe to be this infamous phantom voltage effect and I just would like to make sure I didnt leave anything out.
He was replacing a faulty light fixture in the dining room controlled by a single switch. When he tested the switch he was getting 120 volts on and 48 volts off... I found that the cable leaving the switch to go to some unknown device was a 3 conductor with red, black and white... the red was the switched leg to the light and black a constant power going an outlet perhaps. I thought about phantom voltage and this seems like a perfect scenario where it could happen... I didnt try and measure if the black had a load on it.
I thought that as the travel in the wall for some distance that this could induce a voltage on the switched leg.
I connected a temporary porcelain fixture and the bulb didnt stay on while the switch was off(and initially read 49 volts) also didnt measure a current with it off so I concluded it was phantom voltage..
Am I right?
What other tests can I do to see if it is phantom voltage?
Does an energized conductor with no load induce a phantom voltage? or does it have to have a load?
Thanks guys
