An Engineer in Wonderland – When LED lighting glows at night

Having installed a commercial LED ballast and found that the ‘off’ setting leaves the LEDs glowing faintly, I have heard of a second case of this phenomenon.

The glorious editor (blessed be the ground he walks upon) stayed in a French hotel room that had LED bedside lights, which also continued to glow when ‘off’.

Added note: This blog seems to have been corrupted when it was moved (at this end) from one system to another. Some comments seem to have evaporated, resulting in lost wisdom. The general layman answer to the glow problem seems to be: if glowing occurs after replacing incandescent bulbs with led bulbs, buy a similar led replacement made by a well known reputable brand, and replace one of the glowing ones with that. If it doesn’t glow, maybe replace the rest. Led bulbs vary hugely in quality.

Now we are curious. Has anyone else had such an experience?

I have not fully investigated mine yet, but through some quick comparisons would say that my LEDs have around 100µA passing through them, and it may be 50Hz leakage.

Much as I realise there may be as many causes as instances, including me messing up the installation, but does any one know what is going on here?

Bleed through the primary to secondary EMC capacitor maybe? – but where would the return path be?


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  1. Hi Mike
    I have Christmas tree lights with leds connected in parallel.
    When they are set very dim, the ones nearest the input wire glow first – I am guessing due to voltage drops in the wire. I wonder if you have something similar going on?
    Are yours serial or parallel? – please don’t electrocute yourself finding out!

    Oh my word. Mains gets out so easily into damp plaster.

  2. Just replaced a 150 watt halogen with PIR to a 10 Watt LED with PIR.

    Set up test worked fine. With the LED lights switching off after short time.

    However and here comes the BUT.

    Just one LED in the top right hand corner ( front view) of the nine LED’s on the small square circuit board, remains lit very dimly anytime even in the daylight. I mention daylight because the light has LUX sensor which is set nearly to total darkness before switching on light.

    Could this also be earth leakage as it seems strange only the one LED is affected?

  3. Having found that various LED GU10s exhibit this fault, we have however, not experienced the problem in either our hallway or kitchen-diner. Mid-price ‘bulbs’ in separate toilet-room and the main bath/shower room, all glow when off.
    —Is it perhaps earthing induced by the condensation in these two rooms?

  4. Hi Niran.
    Looks like the only real answer is to get better lights.
    Shame there isn’t a cunning fix.

  5. I have the same issue in my step lights(LED).
    It seems that, more LEDs glows while in Rainy weather conditions. So I feel like LEDs have Earth Leakage and complete its path through Neutral wire , transformer Earth and its earth leakage. So anyone has proper mechanism to mitigate this ?

  6. Hi Striplar
    Did you have long wires to the LEDs?


  7. EDITOR’S WARNING: Dont wire things to the mains like this unless you know what you are doing!!

    I’ve just encountered this ‘problem’ using the circuit illustrated in this page…
    Just in case the link is broken, the circuit is as follows….
    The live feeds a low voltage full bridge rectifier through a 470nF 630V capacitor. The neutral in the return has a 200R resistor for reduce harmonics. There is no smoothing capacitor on the output which in my case feeds the 5 LEDs in series. That’s all there is to it, three components!
    This works really well and it’s clearly leakage currents that are giving rise to the effect. Switching the live and neutral might resolve the problem, it doesn’t happen when I run it through my test lead and an earth leakage trip.

  8. Hello, I’ve experienced this problem also with 20x LED GU10 fittings. All reliably providing enough light when off to walk down the hall way at night. The wiring to the fittings is normal switched live installation and have tried disconnected the earth to the fitting to discount earth leakage. I have purchased some different LED GU10 fittings recently that do not have this ‘feature’ so i’ve installed the new ones in the bedrooms and kept the others for the toilet and hallways.

  9. It affects CFLs too. I have one in my house which flashes briefly every 30 seconds or so, even when the switch is most definitely off. Some kind of mains leakage, or inductance, being stored then discharged into the circuit.

  10. Thanks Tim and Jon.
    Well, we all agree it looks like leakage!
    My back of an envelope calculation is that 100uA from 240V would take about 1nF
    C = 100uA/(250Vx2Pix50Hz)
    If this is right (fingers crossed :-), it is much more than just stray capacitance causing the problem.
    When I fed mine from a lab PSU (linear), the leds went off completely.
    So in my set-up it is almost certainly something to do with the ballast
    – which is going back for replace or refund depending on what the supplier finds out about his other units.
    I should get a scope on it before it goes back, to see if it is 50Hz.
    I am also tempted to try a parallel resistor to bleed 100uA down to a few volts – although these things seem to emit with nearly nothing across them.

  11. My LED GU10 bulbs provide enough light to safely navigate the kitchen when, ostensibly, off.
    I quite like this ‘feature’ so haven’t investigated further so far.
    Being 2-pin GU10 my lamps are internally ballasted and EMC filter leakage to Earth can be ruled out as a cause.
    For some reason the Neutral is switched to my light fitting. This seems quite dangerous, and I wonder if this is how the electrician was supposed to have done it! But, as the Live is always connected I suspect leakage to the earthed fitting is the culpit in my case.
    I may grab a stepladder and a meter this evening and see if I can get some actual data on what is going on in there.

  12. I had a similar problem on an LED ‘mains’ light. The light unit was of the GU11 capsule type fitted with about 20 individual led’s. Some but not all are very slightly illuminated when the main switch is off. In my cas, I am pretty sure that it is due to leakeage in the switch wires. We had a flood about 2 years ago and although The switch has been renewed, the glow only started after the flood and more led’s seem to glow during very damp weather.

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