# Can I run constant power and a three-way switch with three conductors?

Picture this>

• I want to run power from a house to a garage.
• I want power at the garage at all times
• I want a three way switch with one switch in the house and one in the garage to activate the outside light on the garage.

Here is the problem. I believe I made a big mistake. I ran four wires. (black, white, Red, GreenGround) through PVC. Unless I am missing something I don't think there is any way to wire this the way I wanted without one more wire to run to the garage making a total of 5 wires. Am I right? or, is there a way?

• You will need additional wire to do what you want to and be code compliant. Oct 31 '16 at 13:01

There is a way but it is no longer acceptable by code. The reason is the method used will constantly flip the polarity of the hot and neutral lines to the light making either wire and lamp socket parts hot depending on the switches. Edit: This method is dangerous for this reason. The lamp socket shell, which is always supposed to be neutral, can become hot creating a shock or electrocution hazard.

If you can, run a fourth wire. It can be any color save for green and white. I'd go with blue. Make the red and blue the three way leads and let the black stay live the whole time.

Or, Consider a motion detector and leave the red wire disconnected.

Or, Use the red wire for a light only controlled from the house.

• Yes, this was the way I was leaning. Just use one switch in the house and drop the 3 way plan. I really don't want to pull that fourth wire. Thank you! Oct 31 '16 at 14:25
• I updated my comment to include the reason why the three way, three wire with constant power is no longer acceptable. Oct 31 '16 at 14:37

there is another way you can do it, and its all code compliant, but its more complicated.

you run the power there with two of the conductors (lets say black and white as line and neutral) and green as the ground

you use the red wire as a signal wire. now all you need is another switch and signal wire at the garage end. both signal wires get wired into a programmable logic controller at the garage side that is supplied with power at the garage side. you put in a 24vdc power supply at the garage side to give power to the signal wires and wire them to ground, through a standard switch, at their respective device boxes. when you hit the switch, it grounds (or ungrounds), the plc sees that as a change of state and uses that as cue to energize/deenergize an output on the plc I/O rail, and that energizes a relay that you use to control the light.

you can do it yourself pretty easily with some of the siemens plc's. but you may need someone to program it for you.

its a more industrial way to do it, but quite normal in industrial and hvac type installations. and its completely legal because your conductors are within conduit.

• Eh, that's a little over the top. Rube Goldberg would be proud! You can do that with a few relays to implement a flip-flop. But that is even over the top for a simple garage light! Oct 31 '16 at 14:54
• its only over the top if you aren't use to using them. in industrial use, its as common as can be. plc's are much more reliable than multi-relay circuits, and can be programmed for anything you can imagine; time delays, random operation, etc. but certainly out of the range of an everyday residential electrical job. Oct 31 '16 at 15:31

Yet another solution, similar to ppa'a solution but off-the-shelf: run unswitched power, and use home automation equipment to control switches at the far end

• keshlam makes a good point. nowadays, wink style home control units use wifi, bluetooth, etc to make all of this possible an have it accessible remotely from wink switches, phones, etc. Nov 12 '16 at 14:35