New LED Lights Residual Current and Still Glowing After Turned off?


Postby Tall bloke » Mon Jun 25, 2018 4:49 pm

I fitted new lights to both downstairs and upstairs last Tue. The downstairs light is fine, but the upstairs lights glow at night when switched off. We have a 3 way switch downstairs and a single switch upstairs.
As luck would have it we had solar panels fitted last Wed and one of the team was an electrician. I initially thought I had wired the lights wrongly, or insecurely. He checked and said it was good but to change the wires around having seen we had 2 black wires in the feed but 1 had some blue tape marking it. I did this and all was well until I noticed the lights were glowing again last night. The bulls are G9 LED.
I have read that there is normally a residual current in many light fittings and that as LEDs require so little power to work that this residual current can make them glow.
Is that correct? Is it a problem if they glow?

Many thanks in advance.
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Postby Mr White » Tue Jun 26, 2018 4:46 am

There is no "Residual current" in light fittings. (If there were, how come it lasts so long and where is it "stored" Rhetorical question)

What you do have is induction, it has always been there but has become more noticeable since the advent of CFL and LED lamps, it is very common on 2 way switching. You can fit a "suppressor" to stop the effect, (But you have to get the right one) or if your light fitting has multiple lamps change one to an incandescent lamp, or you can leave it as it is and use it as a "night light" there is no harm or danger being caused.
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Postby Tall bloke » Tue Jun 26, 2018 7:24 am

Thanks for the reply. I feel a bit better now knowing their is no real risk.
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Postby ericmark » Sun Jul 01, 2018 9:27 am

Most LED lamps use a simple capacitor as current limiting and have a leak resistor built in, as a result changing the make can change how much light is given out when off.

Basic point is a LED can give 100 lumen per watt, but in order for a small current to flow to work dimming switches and other remote switches the normal is around 75 lumen per watt.

So although it can be cured, it would mean dropping lumen per watt rating, so since it does no harm, just leave it.
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Postby Tall bloke » Sun Jul 01, 2018 8:53 pm

Thanks Eric mark.
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