I'm working on a basement finish project, and need to add a light under the stairs. There are 2 3-way switches near where I want to add the new switch - 1 for the basement lights and 1 for the stairway light. There are 3 14-3 cables running into the box, so I assumed these switches were not at the start of the run. But I opened the box anyway. I found that 1 of the 14-3 cables has the red wire capped (not connected to anything). The black wire from this same cable runs to the common terminal on both switches. The other terminals are connected to red & black on the other 2 cables. I assumed at this point the builder ran out of 14-2 so just used 14-3 instead, and that I had a good source of power. But to be sure I traced the wire, assuming it would run back to the panel. It didn't. It goes to one of the lights on the circuit controlled by 1 of the existing switches. The only thing I can think of is the builder didn't have a single cable long enough for the home run, and used the light's j-box to "splice" the cable for the power source. It seems to me that's the only way the existing circuits would work correctly (which they do). But I don't understand all the 3-way switched circuit combinations. Are there any other possibilities, or can I assume I have a good power source?
Pulling power for new light from 3-way switch
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I find as I get older I find it harder to envision circuits described verbally, but here goes. For your new circuit you will need a hot an neutral (a clear path to ground, not a white conductor being used as a switch return). It sounds like you have a good hot but don't mention any of the neutrals. You mention that the other terminals of the switches are connected to red/black conductors of other cables. It unusual (and maybe not code compliant, IDK) to spread legs of circuits among different cables. I think you really need to figure out which conductor goes where and does what. Make sure everything is dead - there is always the chance that not all cables will be on the same breaker.
Thanks for the reply. I'm afraid I wasn't very clear - sorry about that. There's no spreading of legs among cables. Instead of trying to explain I've attached a crude drawing. I left out the grounds - they're all tied together and attached to both switches on the ground terminal. I've also checked the breakers, and the same breaker is used by both switches. I can keep tracing the wire, but the j-boxes are getting a little difficult to access (I have 6 lights on the basement light circuit). It just seems to me the only way this circuit will work is if the bottom black wire is always hot. I doubt there's a problem with the wiring. I'm the 2nd owner of a 10 year old home in suburban Denver. And a local remodeling contractor (highly reputable) told me a couple years back that it's common for remodelers (and possibly new construction contractors) to use a light fixture j-box to splice wires near the end of a job to save a run to Home Depot. And he told me he's never had an issue with an inspection even after pointing it out to the inspector. Also, based on the handwriting on the panel and the cables it appears whoever wired this wired the rest of the house as well (i.e. don't' think it's a botched DIY).
View attachment Basement Switch Wiring.pdf
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You really should label your drawing.
Are the large blue squares the switches and the small white squares the switches?
Or is the small white squares the switches and the large blue squares the light fixtures?
Plus 3-wire cable has a black, white and red wire, not two blacks and a red.
Electricians don't use 3-wire cable because they ran out of 2-wire cable. Electricians don't run out of 2-wire cable.
You didn't say but I am assuming that the red wire between the switch and the light fixture is not connected to anything at the light fixture. If that is correct the 3-wire cable was probably used so that the the fixture could be a fan/light fixture with the red wire used to power the fan.
Are the large blue squares the switches and the small white squares the switches?
Or is the small white squares the switches and the large blue squares the light fixtures?
Plus 3-wire cable has a black, white and red wire, not two blacks and a red.
Electricians don't use 3-wire cable because they ran out of 2-wire cable. Electricians don't run out of 2-wire cable.
You didn't say but I am assuming that the red wire between the switch and the light fixture is not connected to anything at the light fixture. If that is correct the 3-wire cable was probably used so that the the fixture could be a fan/light fixture with the red wire used to power the fan.
Actually the small white squares are the romex and the 2 blue rectangles are the switches. Labeled diagram below. The cable coming out of the top left goes to either the stairway light or the other 3-way switch on that circuit. Can't tell because it's rocked in. The cable coming out of the top right goes to another 3-way switch on the basement light circuit. The cable at the bottom (with red not connected) goes to a light fixture at the bottom landing of the basement stairs.
View attachment Basement Switch Wiring.pdf
Well, I know of 1 who did just that. I was having an exterior light added to a garage several years ago. The electrician realized he was going to come up short when he started pulling the cable (only by about a foot). He looked in his van, didn't have any more 14-2, so pulled out 14-3 and used that.
Haven't been able to get to the light yet. I have a bunch of sheetrock stacked under it and really don't want to move it. Would be a really strange place for a ceiling fan though - at the bottom landing of a basement stairway in an unfinished basement. And the fixture is a simple lamp holder. FYI - all of this will be re-done when I get to phase 2 of the basement finish in a couple years.
Anyway, there's a really simple solution to this. I own a volt-ohm meter (face palm). I don't know all the functions, but know how to determine if there's current present. Tomorrow I'll open up the switch j-box, hook up the V-O meter to the cable at the bottom and start flipping switches. Don't know why I didn't think of that in the first place.
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I understand your drawing much better now.
Are you saying that the light junction box (the one at the bottom) is a pull chain bulb holder? If so the electrician probably ran 3-wire cable so that that light could also be controlled by a switch if desired. If the red wire is not connected to anything in the fixture box, it can be ignored. You have a constant hot and a neutral at the switch location and can connect your new light and switch.
Are you saying that the light junction box (the one at the bottom) is a pull chain bulb holder? If so the electrician probably ran 3-wire cable so that that light could also be controlled by a switch if desired. If the red wire is not connected to anything in the fixture box, it can be ignored. You have a constant hot and a neutral at the switch location and can connect your new light and switch.
Thanks for the confirmation! I'll still test it tomorrow with the V-O meter to be sure.
The light at the bottom of the stairs is a simple bulb holder without the pull chain. It and the other 6 lights on the circuit are controlled by the right-hand switch in my diagram and another switch at the back door (walk-out basement).
The wiring all makes sense except for the presence of the capped red wire and the fact that the cable coming in from the bottom (assume it's the power source) doesn't run directly back to the panel.
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The fact that the cable comes in from the bottom of the box is not significant. It would be helpful to know the number and kind of cables and the wiring in the box of the bulb holder.
A couple of code cycles back the NEC began requiring neutrals at all switches. An exception was made for 3-way switches. Perhaps the electrician just has a DUH moment.
A couple of code cycles back the NEC began requiring neutrals at all switches. An exception was made for 3-way switches. Perhaps the electrician just has a DUH moment.
I wasn't assuming the bottom cable was the power source based on location. It's just that I can't see any way the circuit can work if it's not. I double-checked a drawing I found on the internet, and my wiring looks exactly like a 3-way circuit with power coming into the switch. Of course with the exception of the capped red wire.
Can you clarify what you mean about the requirement for neutrals at the switch? I have neutral (white) coming in on all 3 cables, and they're all wired together. Are you saying a neutral needs to attach to the switches? I haven't seen a simple 2-way switch that has a terminal for this. Just terminals for 2 hot (line and load).
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A change to NEC now requires that a neutral be available at all switches. That doesn't mean that it is used. When wiring a switch loop, that is when the power comes into the fixture, you only need one wire to bring power to the switch and one wire to return power to the fixture when the switch is on. So in the past when wiring a switch loop you used 2-wire cable.
I guess because so many people wanted lighted switches and remote controlled switches, which require a neutral People were using the ground as a neutral. The NEC began requiring a neutral at all switches even though it wasn't used at the present time. As stated there is an exception for 3-way switches.
You have a neutral because the stairway lighting connect in this switch box.
Examine and describe the wiring in the bulb holder box tomorrow and we can probably figure out how the wiring is run.
I guess because so many people wanted lighted switches and remote controlled switches, which require a neutral People were using the ground as a neutral. The NEC began requiring a neutral at all switches even though it wasn't used at the present time. As stated there is an exception for 3-way switches.
You have a neutral because the stairway lighting connect in this switch box.
Examine and describe the wiring in the bulb holder box tomorrow and we can probably figure out how the wiring is run.
Well, the good news is I tested the wiring at the switch box, and I have current no matter how the switches are set. So it appears I have constant current to pull my new switch/light.
I did go ahead and open up the box at the light as well. There are 3 14-3 cables going into the box. All of the wires are connected together by color (all whites connected, all reds connected, etc.). There's a pigtail off the red bundle that goes to 1 terminal on the lamp, and a pigtail off the white bundle that goes to the other. The black are all wired together but don't connect to anything else in the box. One of the cables goes back to the existing switch box (it's the cable with the capped red). I can't readily track the other 2 cables as they go above a long duct run. I don't understand this circuit, but at this point I've confirmed I have a constant current in the switch box which was the goal.
I need to move the existing switch box about 2 feet, and will need to re-run the cable between the switch box and the light fixture (about 12 feet). Since the red isn't used I'm going to run it with 14-2. Fortunately there's a service loop for the other 2 cables that gives me plenty of slack to work with.
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I would agree.
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