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SaxTeacher 06-27-2008 07:29 AM

Wiring diagram for three-way switches with pilot light
 
I'm preparing to wire a circuit with two three-way switches. One three way switch is in the garage and one is in the house. Both the power and the light fixture are in the garage; the switch in the house will be a switch leg only.

Because the light fixture being controlled by these switches is not visible from inside the house, I'm using a combination switch that includes a pilot light.

As many of you know, wiring a three-way switch with a pilot light is a tricky business - more complicated than just wiring two three-way switches to control a light fixture. I've got a roll of 14-4 (yes, 4-conductor) wire ready...

Neither of the two books I have on electrical wiring ("Wiring Simplified" and "Wiring 1-2-3") provides a wiring diagram for this circuit. I've been searching the internet for a wiring diagram that clearly shows how this needs to be done, but haven't come up with anything.

Any pointers or diagrams would be appreciated!

rjniles 06-27-2008 10:40 AM

There a 3 way switches with small neon pilot lights that glow when the controlled light is off. The way they are wired in the switch is they are connected across the 2 travelers and use the path thru the bulb filament to find a neutral. (There is always power on one of the travelers). If your combination 3 way switches have neon pilots you could wire the same (pilot across the travelers)

rjniles 06-27-2008 10:47 AM

To use regular pilot lights you do need 4 wires between the switches, At the switch where the hot is not connected to the common (meaning the black of the lamp is connected), connect the pilot between the common and neutral. Use the 4th wire to run that common back to the other switch and connect pilot from the 4th wire to neutral. Lacking 4 wire cable you can run 2 two wire cables between the switches.

Stubbie 06-27-2008 11:41 PM

1 Attachment(s)
Try this to go along with rjniles explanations.....drawing is borrowed from levitons technical library

SaxTeacher 07-02-2008 09:24 PM

About that neutral...
 
Thanks for the replies! That diagram is just what I needed. I am almost ready to proceed but I will need one more answer:

I have a floodlight on the outside of my garage. It is currently controlled by a 2-way switch in the garage. I am adding a UF cable buried under the yard to connect it to the house. I will change the 2-way switch in the garage to be a 3-way switch, and will add a 3-way-switch-with-pilot-light in the house.

Since there is already power to the existing switch in the garage, the underground wire from garage to house will be the switch leg only. It will contain two travelers plus the common.

BUT since the 3-way switch inside the house is going to have a pilot light, I will need a neutral there.

The 3-way-switch-with-pilot-light is going to be located inside the house, in a 3-gang box with a couple other switches.

So my QUESTION is:can I tap into the neutral wire already existing inside the box as the neutral needed to make the pilot light work? Or is that unwise/unsafe/not allowed, because the neutral already in the box is from an entirely different circuit? (The neutrals from all the circuits in the entire house DO end up all wired onto the same bar in the panel, right? So how, then, could it matter which one I use?)

Thanks again for your help!

P.S. Please note I am talking about a PILOT LIGHT - that is, an indicator light that lights up when the outdoor floodlights are ON. This is not an illuminated switch, which would illuminate when the lights are off.

theatretch85 07-02-2008 09:50 PM

Using one of the neutrals from another circuit does NOT sound like a good idea. I installed some pilot light 3 way switches in a recent garage complete re-wire project and they don't need the neutral wire for the pilot light to work. The switch is only lit when the load is off (in this case its to find the switch in the dark), and it works just like rjniles said through the travelers. The current required to illuminate the pilot light is next to nothing, so it runs through the filament of the bulb. If the load is disconnected (for instance bad or removed bulb) the pilot light will not light. In thinking about this, I realize what your are looking for is a indicator that shows that the connected light on your garage is on. This would require a neutral, to make it easier and simpler, I would just install a 3-way switch that only lights up when the lights are off. Little backwards than what you want, but its a lot easier than running different wire or re-wiring the lights to pull power from the house instead of the garage.

jimmy21 07-02-2008 11:24 PM

what im thinking...... there would be two ways to do this, either way you would need 4 wires between the two 3-ways

method 1: Power at 3-way, switch leg at the other 3 way. You would need 2 travelers, a neutral, and a switch leg to go back to the first 3-ways pilot light

method 2: power and switchleg both at the same 3 way, dead end at the other side. You would still need 2 travelers over, a switchleg back, and because of the pilot light, you would need a neutral to operate it

Stubbie 07-02-2008 11:25 PM

Quote:

So my QUESTION is:can I tap into the neutral wire already existing inside the box as the neutral needed to make the pilot light work? Or is that unwise/unsafe/not allowed, because the neutral already in the box is from an entirely different circuit? (The neutrals from all the circuits in the entire house DO end up all wired onto the same bar in the panel, right? So how, then, could it matter which one I use?)

Thanks again for your help!

P.S. Please note I am talking about a PILOT LIGHT - that is, an indicator light that lights up when the outdoor floodlights are ON. This is not an illuminated switch, which would illuminate when the lights are off.
I see absolutely no problem with your plan. The neutral your going to use is not a different circuit but the same branch circuit that is powering the switch loop back to the 3-way pilot light.

At the pilot light switch in the house you will need a small jumper from the switched common to the pilot light terminal.

jimmy21 07-02-2008 11:32 PM

you can't use a different circuits nuetral. Yes it will work, and it won't make any difference. But if you do that you can overload the nuetral. Your hot wires are on circuit breakers, limiting them to 15 or 20 amps Which would limit the nuetral to the same, unless you started using nuetrals from other circuits

SaxTeacher 07-02-2008 11:37 PM

Quote:

Originally Posted by Stubbie (Post 135579)
I see absolutely no problem with your plan. The neutral your going to use is not a different circuit but the same branch circuit that is powering the switch loop back to the 3-way pilot light.

At the pilot light switch in the house you will need a small jumper from the switched common to the pilot light terminal.

This sounds incorrect to me based on the wiring diagram that was provided above. Does anyone else think this is wrong? I don't want to wire it this way and have a big POP when I turn on the breaker...

theatretch85 07-02-2008 11:38 PM

The op has indicated that the power for these lights is coming from the garage, not the same box as this switch in question inside the house. If it were getting power at the house side, then there would be no issue here. I don't think its an issue of overloading the neutral, since it would only be powering the pilot light at one switch.

Stubbie 07-02-2008 11:41 PM

Where is the different circuit coming from...? He is replacing the single pole at the garage with a 3 way then cabling back to the house with 4 conductor for his pilot light 3 way switch loop. He is not adding a branch circuit just changing what he has to a 3 way. He could even keep the single pole if he wanted and add the 3 way and still be using the same neutral not a different one.

Stubbie 07-03-2008 12:08 AM

1 Attachment(s)
This is what I understand you have and using your 4 conductor cable

HouseHelper 07-03-2008 07:11 AM

Stubbie: I don't believe he is planning to use 4 conductor between the garage and house (see post #5)... that is why he is considering "borrowing" a neutral... a bad idea!

Best way would be to power the garage light at the house so you would have a hot and neutral from the same circuit there. The 3 conductors to the garage would be the 2 travelers and the switch leg. That makes the switch leg available at the house to connect the pilot light to.

theatretch85 07-03-2008 07:19 AM

Stubbie, your drawing would require a 5 wire cable to complete. It would require a Ground, Neutral, plus 3 hot wires (two travelers, plus a common); and you cant use the ground as the neutral wire. I am guessing this 4 wire cable the op has is 3 wire + ground (bare ground, white, black, red). Unless the op is running conduit the entire distance from switch box to switch box, and pulling individual wires through the only logical way to do this would be what HouseHelper and I have suggested is to power the garage light from the house side of the circuit.


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