I'm trying to figure out a circuit in my home that operates two sets of lights: a set of track lights over the stairwell, and a light fixture at the end of the upstairs balcony. At the bottom of the stairs is a 3-way switch, at the top of the stairs is a 4-way switch, and at the end of the balcony there is what appears to be a 3-way switch. When the switch at the bottom of the stairs or the top of the stairs is flipped, it turns the stairway lights on/off like a regular 3-way circuit. The switch at the end of the balcony also turns the stairway lights on/off like a regular 3-way circuit, but at the same time it turns the balcony light fixture on/off. By flipping the balcony switch you might be turning both lights on, turning both lights off, or turning one on and one off. The two stairway switches have no effect on the balcony lights.
I have two questions about this setup:
- How is the circuit wired to produce this behavior from the balcony switch? I do understand how a basic 3-way circuit works, but I don't understand this extra wrinkle.
- Would it be easy to rewire the circuit so both light fixtures turn on or off together and are controlled by any of the three switches? Or failing that, to rewire the circuit so the stairway lights are controlled by the switches at the bottom and top of the stairs, and the balcony lights are controlled by the switch on the balcony? Easy is the keyword here; I'm not able to run any new wiring, only to change connections inside the junction boxes.
EDIT: As requested, here's a truth table for the possible switch combinations. S1 is a 3-way at the bottom of the stairs, S2 is a 4-way at the top of the stairs, and S3 is a 3-way at the end of the balcony. L1 is the lights over the stairway, and L2 is the light fixture at the end of the balcony.
S1 S2 S3 L1 L2 down down down on on down down up off off down up down off on down up up on off up down down off on up down up on off up up down on on up up up off off
S1, S2, and S3 in combination work like a normal 3-way circuit for L1. Regardless of the positions of S1 and S2, S3 works as an on/off for L2 with down=on, up=off.
EDIT 2: I added photos of the switches below. For each photo, I circled which wires are grouped together in the conduits. The only difference I see from a standard 3-way circuit is that Switch 3 has an extra black wire connected to a traveler screw.