reverse polarity?

[electricalist]

Went to a service call,very old house, not as old as k&t.
Customer says if she turns a switch on for the kitchen the dining room light flickers. Its a 3 way for the kitchen lights, I put in a new one. The panel wasnt labeled so I went down one side turning them off and as i turned off one of the a phase breakers the dining room lights come on but dim. This was also the kitchen lights breaker and is now off.I turn the breaker back on ,turned the dining lights on and found it to be a diff a phase breaker..
My only guess is those circuits are sharing a neutral and theres reverse polarity somewhere and something is feeding it through like a light bulb or the fridge...
Any ideas,,,,thanks

 

[kwired]

Went to a service call,very old house, not as old as k&t.
Customer says if she turns a switch on for the kitchen the dining room light flickers. Its a 3 way for the kitchen lights, I put in a new one. The panel wasnt labeled so I went down one side turning them off and as i turned off one of the a phase breakers the dining room lights come on but dim. This was also the kitchen lights breaker and is now off.I turn the breaker back on ,turned the dining lights on and found it to be a diff a phase breaker..
My only guess is those circuits are sharing a neutral and theres reverse polarity somewhere and something is feeding it through like a light bulb or the fridge...
Any ideas,,,,thanks

I think you should check to make sure the neutral is good, even though it is not a proper multiwire branch circuit - it is still a neutral carrying unbalanced current and you changed the balance when you turned off one side hence the change in voltage across the light in question. For it to work with one side of the circuit off means it is not completely open, but must have a high resistance somewhere on the common supply portion.

 

[electricalist]

The wiring is cloth and there's about 6-8 joints in each light box,the switches were 3-4 way, nothing like a neutral in there. I kinda think the fridge is where there is reverse polarity and that's how the neutral actually makes it back to the panel. I'm really not sure. There's a neutral that makes it back somewhere or they wouldn't work at all.

 

[electricalist]

I think you should check to make sure the neutral is good, even though it is not a proper multiwire branch circuit - it is still a neutral carrying unbalanced current and you changed the balance when you turned off one side hence the change in voltage across the light in question. For it to work with one side of the circuit off means it is not completely open, but must have a high resistance somewhere on the common supply portion.

The fridge could be the high resistance?

 

[kwired]

The fridge could be the high resistance?

Compared to light bulb the fridge would be low resistance - if it is warm enough the compressor is in the circuit anyway.

So if you have open neutral (actually would need to have some conductivity or you lose all loads when opening one ungrounded line) you have a 240 volt series with your light and the fridge. The light will have higher resistance and will have more voltage drop across it. But if you have some neutral continuity to the source it will throw what may be expected off to some degree, compared to totally open neutral.

 

[electricalist]

At the kitchen light I had voltage on hot and neutral but nothin between them. I suspect one of those wires was a neutral after a load.

 

[domnic]

polarity

polarity

Reverse polarity on Chicago 3 way.

 

[electricalist]

I'm sure I'll figure it out. I think reverse polarity and a open neutral because everything works until the kitchen breaker is off. How does a Chicago 3 way work

 

[kwired]

I'm sure I'll figure it out. I think reverse polarity and a open neutral because everything works until the kitchen breaker is off. How does a Chicago 3 way work

First link I found with a good drawing.

The load gets reversed polarity at times - which is a big factor in it no longer being NEC compliant for a circuit with a grounded conductor and also containing a screw shell lampholder.

Was more commonly used in the days when know and tube were being installed, though I have occasionally seen it in other situations.

Worked great when you wanted a set of three way switches between a building and another structure for an exterior light on the either structure - can use one less conductor between the structures assuming you also wanted 120 volts for other loads at the remote structure.

 

[cowboyjwc]

Might want to check that you haven't dropped a phase on the panel too.

 

[kwired]

Might want to check that you haven't dropped a phase on the panel too.

Absolutely, backfeed through 240 volt loads will confuse you the first time you see it, one quick easy check is to turn off all 2 pole breakers in particular the water heater or other direct controlled 240 volt heating elements, contactor controlled equipment generally isolates itself if the control power is lost.

 

[electricalist]

Both circuits are on A phase and I did check that both phases were there with a volt meter then I turned off both 240 v loads. Just to be sure I'm not fooling myself as I was checking things.