LED downlights glow slightly with power off

[canetoad]

Hi,

I have installed a set of LED lights in my upstairs hall (5) to replace the single light. They work great on a narrow area like that. The lights are on a two-way switch and they glow slightly when the switches are orientated with downstairs on and upstairs off. When I switch upstairs on and leave downstairs off they are completely off. If I replace one of the bulbs with a halogen equivalent (GU10) the problem dissappears. They are all connected to the single light feed in parallel.

Can anybody shed some light (ignore the pun) on this and give me a possible cause and solution?

 

[maltaron]

I am fairly certain that LED lamps have a capacitor in them and the residual charge can make the lamps glow. This is the reason that they do not switch off, more like dim off. Replacing one with halogen will deischarge the capacitor immiediately. I have several LED units and ignore any slight glow, they are so cheap to run its not a problem.

 

[P.S.]

yup, I have one that gives out a very faint glow, all others are ok

 

[Steve]

canoetad, I will attempt to explain.

If you've ever delved into electronics, you'll know what a capacitor is. Basically two large plates, pos and neg, with an insulator between. The basics are that this will let through some charge, but it stores most of the charge it recieves. I think.

Now, think about the cable between your two switches. It has three phase conductors. In any position of the two switches, at least one of the cores is always live, and at least one is always dead. When the lights are "off", they are directly connected to the dead core. Because the dead core is right next to a live core, the two act like a capacitor, and an amount of charge is allowed through onto the dead core. Thus some current will flow through the lamps to neutral.

The interesting part is how different types of light deal with this current. Because the current is so small, a 60 watt filament lamp will simply pass the charge over its filament with no noticeable glow or heat, since it takes significant energy to make it glow.
An LED requires so little current to run, that it may well glow slightly due to this current as it passes it over its semiconductor emittor.
The one which makes people panic is the energy saving lamp (CFL). Because there is no direct connection from live to neutral through the lamp, the CFL stores the charge until there is enough to pass through the lamp by way of an electron arc. This manifests itself visually as a slight flicker every 10 or so seconds.

None of the above is anything to worry about.

 

[bpowell555]

I know you guys hate bringing up old threads, but heh I can take the wrath

Will this damage the LED? There are various opinions on line.

I believe I have the 2 way switch scenario, with leakage across the wire. The one way connected lamps have no glow.

Will this damage my new SMDs? I love them and think they're awesome but would hate to think they're life is being foreshortened because of running on extremely low load,

Cheers!

 

[Taylortwocities]

Old topic,
Naughty boy

Anyway. The first line of attack is to check that ALL of the cabling has a cpc and that it is properly connected to earth. This will greatly reduce the problem.

Next possibility is to put one of these across one of the lamps http://uk.rs-online.com/web/p/rc-network/6727032/

Try that and then come back if it ain't fixed.

Ciao!

 

[bpowell555]

Old topic,
Naughty boy

Anyway. The first line of attack is to check that ALL of the cabling has a cpc and that it is properly connected to earth. This will greatly reduce the problem.

Next possibility is to put one of these across one of the lamps http://uk.rs-online.com/web/p/rc-network/6727032/

Try that and then come back if it ain't fixed.

Ciao!

There's no earth going into the ceiling fitting. Will it have to be rewired?

Cheers