Who can help me understand this...?

[ChuckTH]

Okay, this seems to be happening on two separate circuits at my house. 1950s house - newer 200A service in basement and a sub-panel upstairs. The lighting circuits up are essentially ungrounded. (older, silver cloth covered, romex looking stuff. So - I'll explain one of the examples. I have a 20A circuit in basement main panel serves microwave and a light fixture in the pantry. I've followed all the wires in that circuit and opened all the junctions/boxes/outlets etc. It's all newer romex - no "mixing" with older wiring or sharing of neutrals etc. Then I have a 20A lighting circuit coming off my sub-panel that also powers a few bedroom outlets. When I turn off that sub-panel circuit. It all becomes unusable BUT, at one 3-way switch on the hall light and at a light fixture in the linen closet, my "volt sensor" still senses current. (It doesn't seem to be enough to power anything or hurt anyone) but anyway, when I flip the breaker downstairs on that microwave circuit then that "phantom current" in the lighting circuit goes away. I thought maybe I was sharing a neutral or something but like I said, I checked that whole circuit. Is this probably something feeding back through a ground? Like I said, I've got another 2 circuits doing essentially the same thing. What's happening here? How much of a concern is it? and what's the best procedure for running it down? - Thanks!!

 

[Wilko]

Hi - the cheap non contact voltage sensors are reliably unreliable, in my humble opinion. The cable might be live (hot) or it might have a floating (ghost) voltage induced on it from other nearby cabling that is genuinely still live.

 

[ChuckTH]

Hi - the cheap non contact voltage sensors are reliably unreliable, in my humble opinion. The cable might be live (hot) or it might have a floating (ghost) voltage induced on it from other nearby cabling that is genuinely still live.

- nothing else near these wires though.

 

[ChuckTH]

Okay, this seems to be happening on two separate circuits at my house. 1950s house - newer 200A service in basement and a sub-panel upstairs. The lighting circuits up are essentially ungrounded. (older, silver cloth covered, romex looking stuff. So - I'll explain one of the examples. I have a 20A circuit in basement main panel serves microwave and a light fixture in the pantry. I've followed all the wires in that circuit and opened all the junctions/boxes/outlets etc. It's all newer romex - no "mixing" with older wiring or sharing of neutrals etc. Then I have a 20A lighting circuit coming off my sub-panel that also powers a few bedroom outlets. When I turn off that sub-panel circuit. It all becomes unusable BUT, at one 3-way switch on the hall light and at a light fixture in the linen closet, my "volt sensor" still senses current. (It doesn't seem to be enough to power anything or hurt anyone) but anyway, when I flip the breaker downstairs on that microwave circuit then that "phantom current" in the lighting circuit goes away. I thought maybe I was sharing a neutral or something but like I said, I checked that whole circuit. Is this probably something feeding back through a ground? Like I said, I've got another 2 circuits doing essentially the same thing. What's happening here? How much of a concern is it? and what's the best procedure for running it down? - Thanks!!

Just to add.... In the case of the "ghost current" in the example I gave, I've been able to determine that if I unplug the microwave, it goes away. What might that mean? I've read a bit about "induction" and phantom load draws from appliances etc. - but I'm still confused. Anyone?... Thanks

 

[Megawatt]

Just to add.... In the case of the "ghost current" in the example I gave, I've been able to determine that if I unplug the microwave, it goes away. What might that mean? I've read a bit about "induction" and phantom load draws from appliances etc. - but I'm still confused. Anyone?... Thanks

It’s hard to say what’s going on but you the microwave needs to be on its own circuit