HI Folks. I've previously sung the praises of lightrabbit.co.uk / .ie for their GU10 Led lamps, which have proved to me much more reliable than the 'cheapie' eBay bulbs in our shop lighting.
In my stained-glass lamps, I've been using CFL's - which work well. Recently, I thought I'd try some of lightrabbit's B22 LED candle-bulbs.
All looked good in the workshop - two stained-glass lamps with B22 Leds fitted..... ...until I turned off the 2ft fluorescent work-light - which was running off the same 4-way extension lead - at which point both led bulbs emitted a 'pop' and failed.
I contacted lightrabbit - and got this reply
"The reason that these lamps have failed is because they were powered by an extension which was shared with fluorescent lighting. These would have caused a spike in the current which would have damaged the drivers withing the LED's causing them to fail.
I recommend not using CFLs on the same circuit as LEDs."
While I understand the physics behind it (inductive spike from the fluoro choke and all that) - wouldn't you expect that the designers of the led bulbs would add suitable filtering to their bulbs to prevent them just blowing like that?
I've a 60W fluro and 2 LEDs on the same circuit. They're wired so that when I switch on the LEDs come one then if I need the fluro, a 2-way switch turns that on and also leaves the LEDs on[1]. When the 2-way is switched back the fluoro goes off and the LEDs stay on until the main light switch is off. I've had this set-up for only a few weeks but it's OK. The fluoro is quite old with the old gear in it.
[1] This in a shed, so fluoros take time to get going in cold weather. I used to have a 60W incandescent strip as the primary light, but it was pathetic - 2x3.5W, 220 lm LEDs are better. The 2-way used to turn of the 60W filament but now there's no point in bothering with 7W of LED.
It's hard to say. Yes the LEDs should be protected against spikes, but maybe an old choke-ballast fluorescent (if that's what it was) on an extension is asking too much - the fact that both LEDs popped suggests it wasn't marginal.
CFLs and LEDs together should be no problem, so their recommendation doesn't really make sense.
The workshop has 5 or 6 4ft fluoro's, and off 2ft fluoro's on short mains leads plugged in wherever they're needed.
I was a bit surprised at lightrabbit's suggestion - it'd be easy enough to imagine a situation where conventional fluoro's and pendant sockets were on the same circuit - and it'd be a nonsense if turning off the flouo nuked the leds (IMHO)
Well, here's a thing... 20 watt fluorescent lamps are right on the upper limit of inductively ballasted lamp fittings that aren't obliged to have a PFC capacitor fitted which begs the question, does that 20W 2 foot luminary actually have such a PFC capacitor fitted (4.7uF afaicr)?
I'd have thought the presence of a PFC cap would reduce the inductive kick on switch off[1] but without any such PFC cap, there's a real risk of getting a very high voltage spike across any other very low power lamps wired in parallel with the fluorescent luminary.
I suspect even a 15W pygmy lamp (incandescent filament) would act as a very effective 'snubber' and take such narrow spike voltages in its stride but a couple of 3.5W LEDs with their voltage sensitive electronic ballasts are literally 'just begging to be destroyed' by such high speed transient voltage spikes (not just the more sophisticated buck switching converter constant current driver types but also the cruder 'capacitor dropper' types used to drive 20 or so LED chips in series so typical of the cheaper sub 5 watt LED lamps).
I should think the modern electronically ballasted CFLs will be just fine with LED lamps but don't try out a 20 year old SL18 that you've kept unused in its box just for laughs and giggles. However, such "Old Skool" CFLs will be the only type you *can* mix with a fluorescent tube lamp.
The modern CFLs are likely to be just as vulnerable in this usage case, especially the lower wattage types (7 and 11 watts). The higher wattage (20 to 30 watt) might be able to withstand the abuse (as would a constellation of 7 watt electronic CFLs amounting to more than 40 or 50 watts worth - but I wouldn't want to test this theory out with a batch of new CFLs).
Which would include the original CFLs with their magnetic ballast and
*no* PFC capacitor.
I think you simply may have to accept the fact that the amount of 'spike energy suppression' required to protect against magnetically ballasted discharge lamps is simply not economically viable an add-on feature for all but the most expensive of LED lamps and accept the fact that the fluorescent lamp is the prime culprit in this case and in need of 'treatment'.
Rather than wire up one of those mains surge protectors between the fluorescent lamp fitting and the LEDs, it might be better to upgrade the ballast to an electronic one[2] (not replacing the starter switch with an electronic starter - that will just exacerbate the problem!).
[1] TBH, I have my doubts as to whether or not a PFC cap will reduce such voltage spikes sufficiently to eliminate the risk - more likely produce a fatter lower voltage pulse that still exceeds the peak transient voltage rating of the LED lamps' 'electronics'.
[2] In many cases, it's simply cheaper to replace the whole fitting and get a new tube into the bargain rather than trying to buy an electronic ballast unit on its own.
It might seem beside the point to use a 2 foot electronically ballasted tubed fitting in place of a 20W CFL but the fact is you'll enjoy a higher lumen efficacy (90 or so lumens per watt versus 67 Lumens per watt of the typical CFL) along with almost instant full output even in very cold conditions where the typical CFL may well take a minute or two to reach full output plus as much as an extra 10 thousand hours life out of the tube over the more typical 6000 hours of a CFL.
Well, I certainly would. How hard could it be? I mean some switch mode psus do seem to suffer this effect as well. Recently had a DVD macine die when an old style light was turned off. Could one pehaps fit some kind of spike zapper in the old light to earth the overvoltage spike? Brian
HI Brian. Does sound like an attack of the accountants, doesn't it?
I take on board the other comments about doctoring the flourescent fitting - but that's not really the point.
The bulbs that are blowing (in my workshop) are fitted in my hand-made stained-glass lamps, which are sold to people to use in their homes. Now I've got no control over the lighting/wiring etc in my customers' homes, any more than the people who supply the bulbs have over where the bulbs are installed..
Because of the size & shape of the lamps, it's not the easiest thing to replace a blown lamp-bulb - which is why I was thinking 'LED = long life = good' Seems that's not true.
Guess we'll go back to the CFL's that I'd been using before. Thanks A
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