Home>Discussions>ELECTRICAL & LIGHTING>Knob/Tube 3-way. I'm confused....
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Mike
Knob/Tube 3-way. I'm confused....

I am having an upstairs bathroom remodeled and have a wall opened up that exposes some knob tube that I ultimately want to replace.  First, though, I want to understand what's going on.

Fixtures and Switches
1 light at entry of main floor.  1 switch downstairs.
1 light on second floor.  1 switch adjacent to light.

Knob/Tube I can see

2 wires originating from a push button light switch that are in between 2 2x4's   Call them L1(left) L2(right)
1 wire that runs full length of opening ( presuming traveling between the 2 light switches ) that also enters the upstairs light switch box.  Call this wire L3.

Positions of switches and whether current detected with non-contact current sensor

Dowstairs Switch      Upstairs Switch         L1          L2            L3                     2 lights are

Off                              On                            Yes          No           No                        Off

Off                              Off                             Yes          No          Yes                      On

On                              Off                             No            Yes         No                      Off

On                              On                             Yes            Yes        Yes                     On

Can someone explain to me what's going on here?  I have read about Carter 3-ways and just can't get my head around this.

Thanks

 

HandyAndyInMtAiry
Re: Knob/Tube 3-way. I'm confused....

Mike,

First of all, stop trying to figure out the way a 3-way circuit was wired with single stand wire. Also, there is no "On" or "Off" position on a 3-way circuit. It only routes the current to a line that is open to make the circuit open. When you replace that with modern day wire, it will be totally different. What you see, there is no dedicated neutral. You will not follow the same design with modern day wire. Today, you are not allowed to have power enter a light fixture, it must enter one of the switch boxes. It does not matter the number of light fixtures attached, (to a point that is). You just parallel the lights together. Depending on where the power enteres the circuit, will determine how you wire the entire circuit. This is not difficult at all if you have done any kind of residential electrical work. You will need 12-2 and 12-3 wire to design and create this circuit.

Andrew

Handy Andy In Mt Airy NC

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