electrical wiring

[VJ]

Hello,

I have just discovered this weird thing in my apartment. I have a light switch that switches on two spotlights (GU10 fitting). Currently, there is one ledlamp and one halogen lamp (previous tennants). So I decided to replace the halogen one with another led lamp. And this happens:
- remove the halogen lamp -> other (led) lamp lights up very faintly (lightswitch is off!)
- screw in a led lamp -> other lamp goes out, but this one lights up faintly (lightswitch is still off).
I'm no electrician, but this feels very wrong here: even with the switch off, the lamps seem to get power.

I will have an electrician look at it as soon as possible, but in the mean time, what is my best/safest course of action? I decided to remove all the lamps, just to cut out any power.

I'd never have discovered it if I had not replaced the halogen lamp for a led lamp. It does make me worry about other lamps in the apartment though (there are many similar built in lights, and some of them are currently not working; I assumed it was just the bulb, but maybe there is more to it?).

Thanks!


Jörg

[Tjalfe]

is this by chance on a circuit where one of the light switches are illuminated?.. if so, the very little current which passes through to light the, usually neon bulb in the switch is enough to get the LED bulb going. I have the same here with lighted switches in a 3 way switch setup, which makes the CFL bulbs flash faintly

[Umfriend]

I've had that with normal switches. What I was told was that induction from the other wires going through the ceiling/walls might cause just a bit of current to pass-over(? overspraak-achtig? and, well, given how little these babies need to shine

[Chucky Cheese]

Transistor Bias

LEDs bulbs are diodes (Light Emitting Diodes) and restrict electrical flow to one direction. Depending on how the bulb is designed it could be a "forward" or "reversed" bias(refer to PNP or NPN transistor theory) phenomenum that you are seeing. The filament of the halogen bulb was more than likely part of the LEDs circut. A/C travels from positive to negative and with no return path one portion of the A/C sine wave is being consumed at the LED bulb with only half its power...almost as if it is acting like a "half-wave" rectifier.

My gut instinct tells me it is more of a nuisiance than a danger but it is always good advice to have an electrician check things out.

Good Luck!

[VJ]

is this by chance on a circuit where one of the light switches are illuminated?.. if so, the very little current which passes through to light the, usually neon bulb in the switch is enough to get the LED bulb going. I have the same here with lighted switches in a 3 way switch setup, which makes the CFL bulbs flash faintly

No, the lightswitch is not illuminated.

I've had that with normal switches. What I was told was that induction from the other wires going through the ceiling/walls might cause just a bit of current to pass-over(? overspraak-achtig? and, well, given how little these babies need to shine

It might be possible... but the thing is: this is the wall behind a bed. There are lights on the left and on the right; the ones on the left behave like this, the ones on the right do not. I preferred to have all led lights there, but even a faint shine is no good for use in a bedroom...
I actually haven't removed one of the lights on the other side, but with all lights in there none of them shines.

My gut instinct tells me it is more of a nuisiance than a danger but it is always good advice to have an electrician check things out.

Yes...

Thanks guys, I'm a bit more at ease now. I think this may be the reason why the previous tennants just put 4 leds and one halogen. But it just looks weird. I'll have an electrician check it out, but if the wiring is ok than I'll have to resort to putting all halogens.

[LvR]

The LEDs start producing visible light at very low voltages - white ones typically around 3V @ only 50uA ................ depending on your cabling and routing, EMI can quite easily induce low differential voltages on disconnected/switched- off lines and then, because the LED lamps contain a capacitor for DC storage that will act to increase the voltage seen by the LEDs, you may very will end up with sorta "permanent on" LED lamps. IMO the issue will be worse for the guys running at 110V rather 220V because of increased current flow and resulting stronger EMI that can be picked up or induced on cabling. I have the same issues here and my megger and electrician friend cannot find any other cause

[VJ]

The thing is: there appear to be no other electrical cables nearby... It is a fake wall behind the bed with on each side: 1 socket at the bottom, 1 lightswitche reachable from the bed and lights (one near the switch, the other higher). But maybe it is related to how the cables are routed...

The electrician is coming today; I hope he can find the solution. And if not, then it will be all halogen lamps... (I would have preferred leds though: there is about 20 cm between the lights and the bottom of the compartment). The electrician also has to check out a socket that is not working...

[VJ]

Oh, I intend to install some home automation system, so the switch would be replaced in time... The system I'm looking at has different light actuators. On of them is an "all pole" actuator that switches both fazephase and neutral; would this completely eliminate the glow?

I assume it would (unless the cause is through neighbouring cables, but that seems unlikely) as both lines are cut. But can anyone confirm? If so; I would opt for those actuators, even though they are slightly more expensive. Are there downsides to using such all pole actuators?

Jörg

[LvR]

Oh, I intend to install some home automation system, so the switch would be replaced in time... The system I'm looking at has different light actuators. On of them is an "all pole" actuator that switches both faze and neutral; would this completely eliminate the glow?

I assume it would (unless the cause is through neighbouring cables, but that seems unlikely) as both lines are cut. But can anyone confirm? If so; I would opt for those actuators, even though they are slightly more expensive. Are there downsides to using such all pole actuators?

Jörg

IMO if you use the better switch assemblies that cut both neutral and phase you will get rid of the problem - you can actually test/prove it easily before you spend the money by manually removing the common neutral feed from the particular light to the rest of the house

[Umfriend]

The thing is: there appear to be no other electrical cables nearby... It is a fake wall behind the bed with on each side: 1 socket at the bottom, 1 lightswitche reachable from the bed and lights (one near the switch, the other higher). But maybe it is related to how the cables are routed...

Indeed, as long as the cables at some stage are close to other cables you could experience EMI. I do wonder whether an all-pole actuator would, by definition, solve this by my guess is it would be highly unlikely for the issue to remain.

[VJ]

Thanks guys, I really want to put led lights there. I've found a solution of adding a capacitor inbetween, but I will not do those things (I leave all the electricity work to a qualified electrician, but would like to be well informed).
From what I've read, the most common cause has to do with the neutral wire still being connected and causing some issues. Of course, the LED would be lit up purely due to EMI intereference with another cable than I doubt the all pole switch would solve it. But there no cables near the ones for the lights; the all pole switch seems like the easiest solution (and actually another reason to go with that particular home automation system, apart from some poorly positioned lightswitches).

[degrub]

Could just be leakage across the switch - enough to light the LED, but not the halogen. Most switches just interrupt the hot wire leaving the neutral open to ground. Wouldn't take much current, just enough voltage at the LED. Is the halogen closest electrically to the switch ? THe halogen would drop the voltage enough that the LED might not pass current.

[VJ]

It doesn't matter where I put the lights...
1 led: it lights up
2 leds: the one closest to the switch lights up
1 halogen + 1 led: nothing lights up

Does the fact that it is the one closest to the switch that lights up mean it is due to leakage? In which case a new switch might solve it (and then especially one that switches phase and neutral).

The electrician said it is not due to a faulty wiring, but attributed it to old wiring in the building (a bit odd, since the wiring in my apartment is said to be recent). At least I'm reassured now that it is not a problem but rather a nuisance.

[LvR]

IMO my initial explanation is correct when looking at your report-back with the different combinations - the halogen by definition is effectively a resistive load and as such is always able to bleed off the EMI before it gets a chance to be rectified and accumulate in the base of the LED lamp to bridge the LED breakdown voltage.

With 2 LEDs on the same line and only one of them lighting up - quite normal IMO since the breakdown voltages of even 2 identical LEDs from the same batch is not always 100% identical - iow the LED lamp with the lowest breakdown voltage will illuminate first all other things being equal. If you swap the LED's physical positions chances are that the illuminating position will move with the swap - if not then there is still some EMI induced on the piece of cabling between the 2 LEDs on the same line.

I have the same situation in my place and despite every sparky declaring my wiring safe and conforming to spec, they cannot explain the phenomena .................. as an electronics engineer I do however think I have most of it right

[VJ]

I was so surprised to see the lights light up with the switch off, but the explanation makes sense. I haven't tried swapping the leds...

At least now I know everything is ok. I'll get switches that switch of both phase and neutral; the home automation system I'm looking at has them and that will solve the problem. I should probably get such switches on all places where I intend to put leds, just to play it safe (currently, most lights are halogen). they are a thad more expensive but if it solves the problem... :-)

Thanks again for your insights!
I've actually learned a lot from this thread.