Can I ask advice, please. The bulb on my landing light, which is a two-way switch one with an with a switch down stairs and on the landing, ew recently and tripped the upstairs lighting circuit. As you only seem to be able to get LED lights now I replaced it with an LED equivalent to a 60W bulb. Yesterday, the bedroom light and the landing light had only been on for about 20 minutes when the landing light blew again with quite a noise and a smell of burning. The metal bayonet part of the bulb was so hot you could hardly touch it. Has anyone got any clue about this. Or should I just get an electrician in. Thanks Lawrie
If the bulb has a glass shade it's probably due to the base of the LED overheating. A LED, even though of much lower wattage, can overheat if its base gets too hot as glass shades have no ventilation. This doesn't affect old-style filament bulbs. Normally LEDs just fail without noise, but it looks like something else happened.
I'd be suspecting the actual socket arcing myself. It is really impossible to get more volts at the socket than the mains uses unless some pretty creative wiring is at play. Brian
I am using CFLs in those globe shades since they seem to last almost for ever., I think it was a little premature to stop making them as there are some use cases where they work better than leds do. Brian
You could just have been unlucky and got a duff bulb. I have had a LED in the past where its base overheated from new - and failed after a few hours.
You could also have a lose connection at the bulb holder, so I would be wise to turn off the power and check that its screw connections are good, and that the flex to it does not look burnt or discoloured.
+1, and a loose arcing connection in the holder would most likely kill the LED bulb too. Could also be junk on the scket pins. A simple diy job if you're capable.
BAD LED bulb blew its drivers. Probably the LEDS are fine but some cheap chinesium capacitor has blown in it. Oddly enough I have had slightly more failures in LED pendant hung bulbs than the candle ones mounted base downwards.
Just buy another LED bulb from somewhere a bit better than the last one
- I actually found Homebase stocked a decent range - and write that one off to experience.
'so hot you could hardly touch it' is the standard operating temperature for most power semiconductors these days. which will fail at around
200°C internal temperature.
My Raspberry PI runs about 50°C and my old quad core CPU clocks in at around 55°C. Oddly this PC is reporting only 25°C but I am not sure I believe that. When I used to design PA amplifiers the test was whether the power transistors would hiss and turn a wet finger to steam. I tried to keep them below 100°C.
I've had a diode unsolder itself it got so hot...and still work.
'so hot you could hardly touch it' is nothing at all to worry about.
Why do you find that odd? The base contains the crappy electronics that fail through heat, and when hung upside-down the base will get all the trapped heat in a glass shade. I don't remember ever having a base-down LED fail, but I've had more than a few "base-up" LEDs fail, in particular G10s a few years ago (although newer ones are a lot better).
The G10s have a humongous heatsink behind the LEDs, but there's an outer plastic cover, so air circulation around the flared part needs to be good. Some ceiling lampholders aren't too great for this, others are very open.
Yes I once had a cfl fail as the heat glue and solder holding the lamp melted and the tube fell on the floor. I took the bits back to B/Q and they gave me another one with no such fault. I guess it is pretty cramped in these bulbs to get the electronics inside. Another thing to look out for is the cable from the rose to the bulb holder. They get hot with all the heat and age and the insulation cracks and falls off. I also remember when the early CFLs came out they were in a kind of jam jar glass, and heavy as they had a choke inside. I had mor than one break the lampholder bayonet and either fell to the floor or sagged at one side creating arcing that blue the cut-out on the circuit. I don't know if your LED was heavy, but lampholders do fail due to the heat of tungsten bulbs, and it might be time for a new one and a new bit of cable. Brian
You should start by checking mains voltage to see if there is anything abnormal about it.
If you do not own a meter, plug an incandescent bulb into the socket and see if that is excessively bright, indicating a too-high voltage.
This device, is an example of a metering circuit, without needing to wave wires around while working. But it only checks a wall outlet for the conditions it finds, such as mains voltage. The computer I'm typing on, is connected to one of these, so I can watch the power consumption. But by pressing the voltage button, I can check the mains voltage too.
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The UK one has a volt button, just like mine does.
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The reason I'm looking at the voltage in the above answer, is that it is unusual for a LED to blow in the first 20 minutes of life, purely based on temperature. The electrolytic cap in the base, could be a cap with a 2000 hour rating at 105C, which is pretty hot. You might have to push it to 150C, to get it to blow like that (take the 20 minutes to rise to
150C).
LED bulbs should not be operated inside sealed glass globes, as then there isn't enough cooling air. The old incandescent bulbs, they could take the heat, because of the materials they were made of. Similarly, the socket for the incandescent bulb, is designed for significant operating temperature. But LEDs really do best, when there is free air circulating around them. For semiconductor lasers, some of those "extinguish" their optical output, at only 70C. LEDs are related to those.
I have some number of incandescent bulbs left, but they're for test and not for regular usage. Incandescent bulbs are sensitive to voltage, and if you don't have a meter handy, they're the next best thing for a rough eyeball test that the voltage is normal.
LED bulbs are not sensitive to voltage, in the "intensity" sense. If the voltage is 80% of normal, the LED bulb tries to glow at the normal level. If the voltage is 120% of normal, the LED bulb again tries to glow as normal. But the stress the circuit is under, is definitely going to be different, if the voltage is not the nominal value.
At 80% voltage, an incandescent is dim. At 120% voltage, it's bright enough to indicate burn-out is imminent.
Say for example, you operated a LED lamp off the shaver outlet in the bathroom. The LED lamp could blow instantly in there, as the voltage on the shaver circuit can be higher than nominal on a permanent basis. A lot of these electrical goods (even including the Kill-a-Watt), do not list the absolute max voltage they are rated to withstand. I don't really know what a year 2023 or year 2024 LED bulb is rated for, in terms of absolute max. Absolute max, is the voltage that is guaranteed to kill an electrical good. Like my stereo that went into the tip, it could not take voltage excursions on mains, and mains is what killed my stereo. If you have a mains problem, your stereo dying, is a sign of an abnormal situation.
One way to get an abnormal voltage in a house, would be if the house received more than one phase.
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"defining VLN as 100% gives VLL ≈ 100% × 1.73 = 173%" # Line to Line being not what you'd # normally use in a lighting circuit. # It's unlikely multiple phases would be # present in the wiring though (LL for power # instead of the normal LN).
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