Funny switch’s?

[McLintock]

Have two rooms side by side on two different 15 amp breakers. Have a switch for the light and a switch for a fan. Ran 14/3 from the switch box to the ceiling box. Right now I have a lighting pig tail hooked up. Put one switch on the black (the one the pig tail is on) and one switch to the red.

The black switch turns on the light fully, as it should, but I turn that off and turn the red switch on the light is very dim, turn the switch off the light goes off completely. That’s where I am stuck. Both box’s are wired right, power to power, neutral to neutral, ground to ground. Have good voltage. It is a LED light in there.

Any thoughts out there that might help would by much appreciated.


“ shoot low boys their riding shetland ponies”

 

[synchro]

There may be enough capacitive coupling between the black and red wires that the LED is getting enough current off of the red wire to light it up very dimly. That's the problem with having such efficient LEDs

 

[Jraef]

There may be enough capacitive coupling between the black and red wires that the LED is getting enough current off of the red wire to light it up very dimly. That's the problem with having such efficient LEDs

...because the black and red wires are in the same cable for enough distance. Had you used separate 14-2s and put them even an inch apart, no inductive coupling would take place.

 

[McLintock]

There may be enough capacitive coupling between the black and red wires that the LED is getting enough current off of the red wire to light it up very dimly. That's the problem with having such efficient LEDs

That did cross my mind, I first thought something was wrong with the neutral


“ shoot low boys their riding shetland ponies”

 

[texie]

I'm under the impression that the OP has no load on the red lead. Can there be coupling with no load?

 

[McLintock]

I'm under the impression that the OP has no load on the red lead. Can there be coupling with no load?

The red lead only goes from switch box to ceiling box and it’s caped off, so no load


“ shoot low boys their riding shetland ponies”

 

[ptonsparky]

Keep the black off, turn the red on. Light?

 

[synchro]

I'm under the impression that the OP has no load on the red lead. Can there be coupling with no load?

You're correct in that there'll be no inductive coupling (i.e, through the presence of a magnetic field) unless there's a load on the red lead that draws current. However, there can be capacitive coupling because that only requires a voltage to be present.

By the way, I wonder if you could use a 3-way switch to connect the switch leg conductor to the neutral when you want the lamp to turn off. Then even with stray coupling there'll be no voltage across the lamp when it's turned off because both sides of the lamp will be at the neutral voltage.

For sake of argument, 404.2(B) says:
Grounded Conductors. Switches or circuit breakers shall not disconnect the grounded conductor of a circuit.

Now if the OFF state of the 3-way connection above, the grounded conductor is still connected just like it is in any lamp circuit with a neutral. So, I'd argue that the three way switch does not disconnect the grounded conductor of a circuit. But in the OFF state the switch leg is also connected to the grounded conductor just to drain off any very small stray current. Now in the OFF state the switch leg does disconnect from the grounded conductor, but as noted above the grounded conductor of the circuit going to the lamp is still connected.
I don't think the reasons for 404.2(B) are being violated in such a connection. It disconnects the lamp from the ungrounded wire to turn the light off, and so no voltage is present at the lamp that could cause a safety issue when it's turned off. And there are no conductors in parallel that could cause other issues.
What do others think about this? I can see that someone might object just because it's not normally done.

 

[LarryFine]

Any thoughts out there that might help would by much appreciated.

Try an incandescent bulb instead or in addition.

 

[Little Bill]

Sounds like it is wired for a future ceiling fan w/light. Once that is place I don't think the OP will see the problem.

 

[synchro]

Try an incandescent bulb instead or in addition.

If it has a replaceable bulb that would be the easiest thing to do.

 

[McLintock]

Try an incandescent bulb instead or in addition.

I’ll try that also


“ shoot low boys their riding shetland ponies”

 

[McLintock]

You're correct in that there'll be no inductive coupling (i.e, through the presence of a magnetic field) unless there's a load on the red lead that draws current. However, there can be capacitive coupling because that only requires a voltage to be present.

By the way, I wonder if you could use a 3-way switch to connect the switch leg conductor to the neutral when you want the lamp to turn off. Then even with stray coupling there'll be no voltage across the lamp when it's turned off because both sides of the lamp will be at the neutral voltage.

For sake of argument, 404.2(B) says:
Grounded Conductors. Switches or circuit breakers shall not disconnect the grounded conductor of a circuit.

Now if the OFF state of the 3-way connection above, the grounded conductor is still connected just like it is in any lamp circuit with a neutral. So, I'd argue that the three way switch does not disconnect the grounded conductor of a circuit. But in the OFF state the switch leg is also connected to the grounded conductor just to drain off any very small stray current. Now in the OFF state the switch leg does disconnect from the grounded conductor, but as noted above the grounded conductor of the circuit going to the lamp is still connected.

Are you saying connect the neutral to the common screw, and the light leg and the hot to the two other screws?


“ shoot low boys their riding shetland ponies”

 

[CountryBoy19]

Sounds like it is wired for a future ceiling fan w/light. Once that is place I don't think the OP will see the problem.

Maybe, maybe not. My ceiling fans glow dimly with the fan on and lights off with LED bulbs. That's with single-wire to the fixture using the pull-chains to switch them. Adding an incan bulb fixes it.

I'm curious to know the thoughts on what synchro suggested...

 

[McLintock]

Sounds like it is wired for a future ceiling fan w/light. Once that is place I don't think the OP will see the problem.

I hope that is true, most the houses I do all have can lights in the room, so we fire those up to give light to the other trades. When I wired up the switch’s a two months ago (only a family of three building a log cabin, so it takes them a while) I did not even turn that switch on, because it was not hooked up to anything.


“ shoot low boys their riding shetland ponies”

 

[texie]

You're correct in that there'll be no inductive coupling (i.e, through the presence of a magnetic field) unless there's a load on the red lead that draws current. However, there can be capacitive coupling because that only requires a voltage to be present.

Ah, I see.

 

[synchro]

Are you saying connect the neutral to the common screw, and the light leg and the hot to the two other screws?

Not quite. The light leg would be connected to the common screw. One of the other two screws (normally used for travelers) would be fed by the hot, and the second screw would be connected to a tap off of the neutral conductor that goes to the light. The neutral side of the light would be always solidly connected and not switched, as required by the NEC.
It would connect the light leg to the hot to turn the light ON, just as it's normally done. But instead of leaving the light leg "floating" and susceptible to stray coupling when the light is turned OFF, the three-way would make sure the light leg voltage is near zero by tying it down to neutral.

 

[synchro]

I just noticed that in my post #8 above when I said:
"Now in the OFF state the switch leg does disconnect from the grounded conductor, but as noted above the grounded conductor of the circuit going to the lamp is still connected."
It should be "Now in the ON state ..."

 

[McLintock]

Not quite. The light leg would be connected to the common screw. One of the other two screws (normally used for travelers) would be fed by the hot, and the second screw would be connected to a tap off of the neutral conductor that goes to the light. The neutral side of the light would be always solidly connected and not switched, as required by the NEC.
It would connect the light leg to the hot to turn the light ON, just as it's normally done. But instead of leaving the light leg "floating" and susceptible to stray coupling when the light is turned OFF, the three-way would make sure the light leg voltage is near zero by tying it down to neutral.

Next time i am there I will try that out


“ shoot low boys their riding shetland ponies”

 

[GoldDigger]

You're correct in that there'll be no inductive coupling (i.e, through the presence of a magnetic field) unless there's a load on the red lead that draws current. However, there can be capacitive coupling because that only requires a voltage to be present.
...
...

Just to complicate things, it is common usage to refer to the voltage produced by either capacitive or inductive coupling as "induced" voltage. In residential situations you rarely if ever have the combination of high current and wire layout necessary to get a noticeable voltage from inductive (magnetic) coupling.