Crofter Posted February 6, 2017 Share Posted February 6, 2017 Bit of an odd one this. Popped into the kitchen after lights out and spotted that a GU10 task light was glowing very faintly. The lamp is a SMD type. At first I thought that it must have been left on and the lamp had failed, but, no, it was switched off at the wall. 'On' works, but 'off' doesn't! It's only the very faintest glow but obviously there is something wrong. I'm not convinced that the previous owners of this house knew what they were doing. I swapped out a single socket for a double and found that the earth was connected to the back box but not the socket! And the plumbing is pretty poor too, waste pipes laid with sections that remain full of water etc. Anyway, any suggestions for what might be causing the symptoms with the light? It's a single downlighter on its own switch. Oh and I did remove the lamp just to be sure, it has stopped glowing now, so it looks like I haven't discovered a source of zero point energy after all Link to comment Share on other sites More sharing options...
Steptoe Posted February 6, 2017 Share Posted February 6, 2017 Its a very common problem, I have a light in my kitchen that flickers for a few seconds when they are turned off, bank of 6, Fitting a snubber would be the usual fix, I just have not got round to doing mine yet, its only been 8 years.! Its merely an induced voltage, and as LED uses so little current its enough to make it glow, Is it on a 2way switch,? If so, occasionally switching the common Line to sit beside the cpc (if its 3core) sometimes cures it. Link to comment Share on other sites More sharing options...
Crofter Posted February 7, 2017 Author Share Posted February 7, 2017 This one had been turned off for about twenty minutes when I noticed the glow. There's only a single switch to it. I wonder where the induced voltage could be coming from... can I experiment with turning other things off? I was worried it was a sign of some very dodgy wiring somewhere...! Link to comment Share on other sites More sharing options...
Onoff Posted February 7, 2017 Share Posted February 7, 2017 A lot of folk use these: http://www.maplin.co.uk/p/rc-contact-suppressor-rg22y Link to comment Share on other sites More sharing options...
Bitpipe Posted February 7, 2017 Share Posted February 7, 2017 I have a different issue (sorry for hijack). In our study we have 5 LED spots on a MK dimmer module. When they're set low, their brightness can suddenly increase for a moment and then dim again. Spark has swapped out the dimmer module a few times now, wondering what else it could be. Link to comment Share on other sites More sharing options...
Nickfromwales Posted February 7, 2017 Share Posted February 7, 2017 What's the MININUM loading of the dimmer? You may need to add some resistance to the load to control it properly. Link to comment Share on other sites More sharing options...
Steptoe Posted February 7, 2017 Share Posted February 7, 2017 2 hours ago, Bitpipe said: I have a different issue (sorry for hijack). In our study we have 5 LED spots on a MK dimmer module. When they're set low, their brightness can suddenly increase for a moment and then dim again. Spark has swapped out the dimmer module a few times now, wondering what else it could be. Are they proper dimmable LEDs? Ate they mains or elv,? if elv are they proper drivers or simple transformers, are they dimmable? Is it the proper type of dimmer,? Leading edge or trailing edge,? As above, what's the minimum loading on the dimmer, lots are 20 or 40w minimum, that can be quite a few LEDs all maxed out,! Link to comment Share on other sites More sharing options...
Bitpipe Posted February 7, 2017 Share Posted February 7, 2017 3 hours ago, Steptoe said: Are they proper dimmable LEDs? Yes 3 hours ago, Steptoe said: Ate they mains or elv,? if elv are they proper drivers or simple transformers, are they dimmable? Mains 3 hours ago, Steptoe said: Is it the proper type of dimmer,? Leading edge or trailing edge,? As above, what's the minimum loading on the dimmer, lots are 20 or 40w minimum, that can be quite a few LEDs all maxed out,! Like this Can only assume so, we have a similar setup in the kitchen (6 spots) and living room (8 spots) with no issue so could be the min load. 5 hours ago, Nickfromwales said: What's the MININUM loading of the dimmer? You may need to add some resistance to the load to control it properly. I'll ask Smiffy and tell him you're offering to come and fix it Link to comment Share on other sites More sharing options...
Temp Posted February 7, 2017 Share Posted February 7, 2017 19 hours ago, Crofter said: Anyway, any suggestions for what might be causing the symptoms with the light? It's a single downlighter on its own switch. Oh and I did remove the lamp just to be sure, it has stopped glowing now, so it looks like I haven't discovered a source of zero point energy after all Two possibilities.. 1) Some LEDs seem to have a phosphor coating that continues to glow for quite a while after being turned off. I have an array of 12 LEDs and 4 or 5 seem to glow more than others. Go back an hour or two later and they are dark again. 2) Coupling between the Live and Switched live in the drop down to the switch. I have an array of 6 LED in a bathroom that continue to glow indefinitely when switched off. Replacing one LED with a halogen turns off the other LEDs but that only masks the problem not cure it (eg the circuit still consumes a little power when "off"). Link to comment Share on other sites More sharing options...
Steptoe Posted February 7, 2017 Share Posted February 7, 2017 2) That's just induced, see my earlier post, 8 minutes ago, Temp said: Two possibilities.. 1) Some LEDs seem to have a phosphor coating that continues to glow for quite a while after being turned off. I have an array of 12 LEDs and 4 or 5 seem to glow more than others. Go back an hour or two later and they are dark again. 2) Coupling between the Live and Switched live in the drop down to the switch. I have an array of 6 LED in a bathroom that continue to glow indefinitely when switched off. Replacing one LED with a halogen turns off the other LEDs but that only masks the problem not cure it (eg the circuit still consumes a little power when "off"). Link to comment Share on other sites More sharing options...
Crofter Posted February 7, 2017 Author Share Posted February 7, 2017 38 minutes ago, Temp said: Two possibilities.. 1) Some LEDs seem to have a phosphor coating that continues to glow for quite a while after being turned off. I have an array of 12 LEDs and 4 or 5 seem to glow more than others. Go back an hour or two later and they are dark again. 2) Coupling between the Live and Switched live in the drop down to the switch. I have an array of 6 LED in a bathroom that continue to glow indefinitely when switched off. Replacing one LED with a halogen turns off the other LEDs but that only masks the problem not cure it (eg the circuit still consumes a little power when "off"). It's not 1, because I removed the still-glowing lamp and it instantly went out. It's a 3w LED so in its dimly lit state cannot be consuming any meaningful amount of power... can it? Link to comment Share on other sites More sharing options...
Steptoe Posted February 7, 2017 Share Posted February 7, 2017 12 minutes ago, Crofter said: It's not 1, because I removed the still-glowing lamp and it instantly went out. It's a 3w LED so in its dimly lit state cannot be consuming any meaningful amount of power... can it? Its 'free' power Its basically stealing a miniscule amount of current from somewhere else, I don't even think you could measure it on a normal clamp meter, you'd need a mA clamp, (leakage clamp) to get any measurement. Link to comment Share on other sites More sharing options...
Guest Alphonsox Posted February 7, 2017 Share Posted February 7, 2017 You're not near a transmitter of some kind are you ? I used to have the same problem with CFLs when I lived in France. A combination of extremely dodgy aluminium wiring and a police transmitter a few hundred meters away. Link to comment Share on other sites More sharing options...
Jeremy Harris Posted February 7, 2017 Share Posted February 7, 2017 (edited) I've had this when we converted to LED lights in our bathroom. The cause was as temp suggests, an induced current between the switched and non switched live. It's pretty common in older houses where an earth wire doesn't run up the light fitting. In our case, just making sure the earth conductor was connected fixed it, as it removed the induced current (or rather shunted it to earth). A fair few LEDs will glow with just a mA or two, and it's pretty easy to get that sort low current just from induction. Some LED types are worse than others in terms of susceptibility to this. Those with small AC/DC constant current inverters in the base are often OK, but there are a fair few around that use a capacitive dropper (strictly speaking a reactive current limiter) and they are susceptible, as are the types that use a long string of series LEDs and a simple rectifier/resistor arrangement (like the newer filament-type leds). The cause of the problem a fair bit of the time is in the earth not being connected in the feed to the light fitting. A fair few pendant fittings, and some others, are just two-wire, with no earth needed, and, although the earth conductor should be earthed in the switch box, it's not that uncommon in my experience to find a bit of sloppy wiring there, with the earth to the ceiling let disconnected. That was the case with every single light in our current house, except for the kitchen. Whoever wired it, just cut the ceiling earth of short, I think to reduce the clutter in the switch back box. Not at all clever, in my view. Edited February 7, 2017 by JSHarris Link to comment Share on other sites More sharing options...
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