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Black Forest
07-31-2015, 12:54 AM
I wanted to change out a normal incandescent light fixture for a LED light fixture. No problem. There were only two wires going to the incandescent light fixture. So I mount the LED fixture and connect up the two wires to the fixture. The LED light lights up but very dim. I flip the switch and the light comes on bright.

In my electrically challenged mind I am not sure what is going on except I have some stray low level power coming from somewhere.

What do I need to do to figure this out? There is no provision for the earth ground wire on either fixture.

danlb
07-31-2015, 01:31 AM
The first thing you want to determine is whether you have a straight mechanical switch, or one that is electronic. A mechanical switch will open the path. An electronic switch may have a few milliamps of leakage across the load. The motion sensing switches in my hall use the light bulb as a path to provide current to the Passive Infra Red (PIR) sensor.

To keep the LED light from flashing on and off in my hall, I added a 5 watt night light to the light socket in parallel with the LED light. This provides a low resistance path for the current, and keeps the current through the LED low enough that it does not glow.

If you have a mechanical switch, then there is a problem with something leaking voltage onto the hot wire.

Dan

Black Forest
07-31-2015, 02:01 AM
The first thing you want to determine is whether you have a straight mechanical switch, or one that is electronic. A mechanical switch will open the path. An electronic switch may have a few milliamps of leakage across the load. The motion sensing switches in my hall use the light bulb as a path to provide current to the Passive Infra Red (PIR) sensor.

To keep the LED light from flashing on and off in my hall, I added a 5 watt night light to the light socket in parallel with the LED light. This provides a low resistance path for the current, and keeps the current through the LED low enough that it does not glow.

If you have a mechanical switch, then there is a problem with something leaking voltage onto the hot wire.

Dan

Yes it is an electronic switch. It is a switch that I added a wireless remote switch that just sticks on the wall. I am not sure how I could add anything to "use up" the leakage. Any suggestions?

RichR
07-31-2015, 02:02 AM
Is the switch the illuminated type so you can find it in the dark? If so the built in light might be supplying the current.

darryl
07-31-2015, 02:09 AM
Even with a mechanical switch there can be enough capacitance in the wiring to allow a small current to flow, enough for a simple arrangement of leds to glow slightly. An electronically powered led light won't have enough juice to provide for this, but a simple series arrangement of leds with a series resistor could respond. There's two ways that power is provided to a light socket- one is where the ac voltage comes to the switch, then feeds on to the fixture, and the other is where the full ac voltage is fed to the socket and the switch completes the circuit to ground when it's turned on. In the latter case the return wire going to the switch has some capacitance to the ground or neutral wire, and a small but not zero current can flow. Because modern leds are quite efficient they will produce some light even with almost zero current flow. I haven't seen this happen directly but it's plausible.

danlb
07-31-2015, 02:14 AM
Yes it is an electronic switch. It is a switch that I added a wireless remote switch that just sticks on the wall. I am not sure how I could add anything to "use up" the leakage. Any suggestions?

There are a few ways to do that.

You can add another outlet in parallel with the light bulb, and then put a 2 or a 5 watt night light in that outlet. The 5 watt bulb will light up with the LED.

You can look for a different bulb that is NOT dimming compatible. It may or may not flash on and off.

And you can install switches that are compatible with dimmable LEDs.


Dan

danlb
07-31-2015, 02:18 AM
...
the other is where the full ac voltage is fed to the socket and the switch completes the circuit to ground when it's turned on. In the latter case the return wire going to the switch has some capacitance to the ground or neutral wire, and a small but not zero current can flow. Because modern leds are quite efficient they will produce some light even with almost zero current flow. I haven't seen this happen directly but it's plausible.


If capacitance is the problem, would it not light for a fraction of a second and then go out? I don't see a 10 to 20 foot length of wire having enough capacitance to charge a circuit when one end is not terminated.


Dan

10KPete
07-31-2015, 02:46 AM
No one has suggested a floating neutral problem. Simple measurement: hot to good ground; hot to neutral. Better be the
same!

Pete

The Artful Bodger
07-31-2015, 03:14 AM
I suspect a leaking switching and the way to cure your problem is to put 'real' load across the lines that feed the light fixture. Low voltage night lights have been suggested and I agree.

yf
07-31-2015, 04:39 AM
Check if the circuit is back wired.
Meaning if the switch is after the load on the neutral.
If the hot wire is cut by the switch, you should not have any current going through fixture unless you have an ungrounded neutral.
Also check if the box is being used as a neutral.
I've seen it often here, where someone wants to install a timer on a light, and since this is the first city to be electrified, originally the fixtures all had pull chains and there were no outlets. (Early appliances were connected to light sockets.)

So, much later, someone ran a 2 conductor wire down a wall to install a wall switch, there is no neutral, because the 2 conductor, is hot feed to switch and switched hot to fixture. So to make timer work, someone (not me :))grounds timer neutral to box.

(its not always a timer. It could be anything, even an outlet which I've seen plenty too)

below you can clearly see the fender washer and the now bare wire that was under it. The insulation burned when the wood screw holding the washer got loose when the wood dried up and was making only intermittent contact with the box and was arcing when under load.
The tenants refrigerator was plugged into the outlet on the back side of the wall.
Most probably done by the superintendent decades ago. There was no neutral in that box. Just 2 switched hots and 2 hot feeds.

http://img.photobucket.com/albums/0603/machines/20150615_171635_zpsfx55t8hm.jpg (http://smg.photobucket.com/user/machines/media/20150615_171635_zpsfx55t8hm.jpg.html)

The Artful Bodger
07-31-2015, 06:18 AM
I think we should bear in mind that Black Forest lives in Germany where the wiring scheme may be somewhat different. Ha ha, it might even be metric!:D

Black Forest
07-31-2015, 06:37 AM
I think we should bear in mind that Black Forest lives in Germany where the wiring scheme may be somewhat different. Ha ha, it might even be metric!:D

Yes we use metric electricity. The wiring here in Germany is pretty standard except we use 220v and up for everything. Normal household is hot, neutral, and earth ground. Everything is on a ground fault main circuit breaker. Sometimes that is a real pain but sometimes it saves a real pain!

The Artful Bodger
07-31-2015, 06:43 AM
BF, can I ask do you normally switch two or just one conductor to a light fitting?

boslab
07-31-2015, 07:18 AM
You sound like you have live switching, the Swiss used to zap me often, the fixture is live, current flows when the switch is closed, essentially in the N line, check fitting to earth with it off and on, whatever voltage, it will be the same with a meter, I crushed a lamp and got zapped, the on of is in the return not the feed as it were
Regards
Mark

Lee Cordochorea
07-31-2015, 08:13 AM
Even with a mechanical switch there can be enough capacitance in the wiring to allow a small current to flow, enough for a simple arrangement of leds to glow slightly.Capacitive reactance is inversely proportional to frequency. If your mechanical switch passes any measurable current at 60 Hz, it's a bad switch.

GSWayne
07-31-2015, 12:16 PM
Switching to a LED bulb presumably to save electricity and then adding a permanent 5 watt load to it seems like a bad idea. The night light running 24/7 would consume more energy than the LED bulb would if it was used several hours per day. I think you need to fix the switch. If it does have leakage current it was wasting power when you had the old light bulb, you just could not see it.

danlb
07-31-2015, 12:31 PM
It's not a bad switch. See post #3. It's an electronic switch with a remote control. I'm assuming that it's radio, though it could be IR or many other methods.

It needs to have some current flowing to power the radio receiver in the switch. Since most light switches just interrupt the hot line, the neutral is frequently not routed through the mounting box that the switch is in. With no neutral, the power HAS to flow through the load.

If neutral is available, it's not a bad idea to use a switch that is designed to use it. As an example, the X10 remote wall switch that uses the neutral and does not pass current through the load when off. The X10 model is WS13A, although that is in the wrong voltage. :) http://www.x10.com/ws13a.html#

Dan

danlb
07-31-2015, 12:38 PM
Switching to a LED bulb presumably to save electricity and then adding a permanent 5 watt load to it seems like a bad idea. The night light running 24/7 would consume more energy than the LED bulb would if it was used several hours per day. I think you need to fix the switch. If it does have leakage current it was wasting power when you had the old light bulb, you just could not see it.

It's not as bad as it seems. The voltage is so low that the night light does not even glow. I never put a meter on mine to check it, but suspect that it's less than a watt.

Dan

PStechPaul
07-31-2015, 04:47 PM
The main problem with the night light is that it will be on full brightness whenever the LED lamp is on, and unless you have a use for it, the power is wasted. Maybe a better load would be a charger and an emergency lamp or a power tool that gets used occasionally. It would draw essentially nothing while the switch is off and would charge only when on. Small chargers usually don't draw much power, although they can draw considerable current. Swiching types introduce a capacitive load, and transformer types are inductive, so they might draw 100 mA at 120V, or 12 VA, but only maybe 2W unless they are actively charging. The electric meter will only read the true power, and a 2W load will cost less than a penny a day.

Black Forest
08-01-2015, 01:23 AM
I will put the old light back up and use the LED light somewhere else.

Thank you all for the help.

Paul Alciatore
08-01-2015, 03:55 AM
In making your decision, keep in mind that if this electronic switch is leaking some current, it will do so with the old light as well. But that light just did not show any light from it. You will still be wasting electricity on a constant basis weather you use the old or the new, LED lamp.

I would look at replacing that switch with one that does not leak.

A good test for this leakage would be to disconnect one of the wires at the electronic switch and see if the LED bulb goes completely off. If so, then the switch is probably at fault. If not, then there is something else in the system that is causing the problem.

J Tiers
08-01-2015, 10:04 AM
Yes we use metric electricity. The wiring here in Germany is pretty standard except we use 220v and up for everything. Normal household is hot, neutral, and earth ground. Everything is on a ground fault main circuit breaker. Sometimes that is a real pain but sometimes it saves a real pain!

And you probably have those insane "schuko" plugs and outlets. Those should be illegal.

The French have it better, a very similar plug, but with a pin and socket grounding system, not those incredibly stupid little side contact prongs that seem always to be bent making no contact.

Europeans make fun of US plugs, but the Schuko is proof positive that a far worse and less functional system can be invented. And it is GERMAN, of all things!

LKeithR
08-01-2015, 01:49 PM
...I would look at replacing that switch with one that does not leak...

Finally! Someone who gets it! If you've got a defective piece of equipment it should be replaced. Anything else is just a patch and is potentially dangerous. Electricity is not something to fool around with...

danlb
08-01-2015, 04:35 PM
Finally! Someone who gets it! If you've got a defective piece of equipment it should be replaced. Anything else is just a patch and is potentially dangerous. Electricity is not something to fool around with...

It appears that I was not clear enough. Maybe an example would help?

A lighted switch has similar needs if there is no neutral wire in the mounting box. Look at the explanation at http://diy.stackexchange.com/questions/54105/how-does-an-illuminated-switch-light-up-without-a-neutral to see how it passes some current through the load.

A similar example is an electronic dimmer switch without neutral. http://www.smarthome.com/sc-what-to-do-if-you-dont-have-a-neutral-wire.

Dan

Arcane
08-01-2015, 05:25 PM
It appears that I was not clear enough. Maybe an example would help?

A lighted switch has similar needs if there is no neutral wire in the mounting box. Look at the explanation at http://diy.stackexchange.com/questions/54105/how-does-an-illuminated-switch-light-up-without-a-neutral to see how it passes some current through the load.

A similar example is an electronic dimmer switch without neutral. http://www.smarthome.com/sc-what-to-do-if-you-dont-have-a-neutral-wire.

Dan

I have several lighted switches that work exactly like that. Remove the light bulb and the switch light goes out.