Burning of LED lights

[digimart]

I have installed a few 5W and 9W LED down-lights in my shop ( 220V AC ).
Have been using similar lights in other locations with no issue. But here after every 10 to 12 days one the light gets OFF.
What happens is that one of the LEDs get burnt, and as all the LEDs are connected in series so the light shuts down. Then I change that one specific LED, and the light starts working again, but it happens again after another 10 days or so.
There can be number of reasons for this. Can you guide from where should I start my investigation and check out all the possible causes of this problem ?

[inetdog]

I have installed a few 5W and 9W LED down-lights in my shop ( 220V AC ).
Have been using similar lights in other locations with no issue. But here after every 10 to 12 days one the light gets OFF.
What happens is that one of the LEDs get burnt, and as all the LEDs are connected in series so the light shuts down. Then I change that one specific LED, and the light starts working again, but it happens again after another 10 days or so.
There can be number of reasons for this. Can you guide from where should I start my investigation and check out all the possible causes of this problem ?

The most likely explanation is that the voltage or number of lights you have in series is different in your shop than in the other location.
When you try to put complete LED modules or just LED elements in series, there may be problems with too much current flowing, which will cause one of them to fail early. But all of them are getting too much current and generating too much heat, to eventually a different one will fail.

Strings of LED lights, as for decorative lighting or rope lighting, are made with a number of LEDs and a series resistor to limit the current, all of which is designed to operate the LEDs at a safe power rating when the rated voltage is applied.

Can you tell us more of what kind of LED downlight units you are using and how many of them you have placed in series?

[digimart]

The most likely explanation is that the voltage or number of lights you have in series is different in your shop than in the other location.
When you try to put complete LED modules or just LED elements in series, there may be problems with too much current flowing, which will cause one of them to fail early. But all of them are getting too much current and generating too much heat, to eventually a different one will fail.

Strings of LED lights, as for decorative lighting or rope lighting, are made with a number of LEDs and a series resistor to limit the current, all of which is designed to operate the LEDs at a safe power rating when the rated voltage is applied.

Can you tell us more of what kind of LED downlight units you are using and how many of them you have placed in series?

I like to clarify that I have not placed by downlights in series. they are independently placed. I was just referring that within a light the LEDs are connected in series.
Further, I am attaching a picture of a downlight similar to the ones used by me at my shop.
LED Downlight.jpeg

[inetdog]

I like to clarify that I have not placed by downlights in series. they are independently placed. I was just referring that within a light the LEDs are connected in series.
Further, I am attaching a picture of a downlight similar to the ones used by me at my shop.
[ATTACH=CONFIG]2432[/ATTACH]

That is much easier to understand, thank you.

The possibilities now are that the lamps are defective or poorly designed, that they are being exposed to a higher than expected voltage, or that the lamp assembly is not well enough ventilated to keep the LED and driver temperature to a low enough level for long life. In any of these cases, it would be likely that one of the several LEDs in the assembly would fail first. If the problem were simply aging, I would expect the light output from all of the LEDs to be somewhat degraded before the first one failed.

You can check the voltage rating on the downlight assembly and on the lamp element within it if it is removable. You can check the temperature of the outside surface of the assembly and also look to see whether ventilation holes in the unit are being blocked by the way you are mounting them. And it would be helpful to know whether the single LED which eventually burned out started to look different from the others a while before it finally failed.
Was the failing LED always in the same position (inner versus outer ring, etc.) within the assembly?

Is it possible to try replacing the failed LED with a good one from another failed unit? Or is it a sealed assembly?

[digimart]

Is it possible to try replacing the failed LED with a good one from another failed unit? Or is it a sealed assembly?

Yes its possible, that I do the same, replace the failed LED with a new one.

[inetdog]

Yes its possible, that I do the same, replace the failed LED with a new one.

Taking a close look at the picture you posted of a similar luminaire, I see a very substantial finned heat sink on the back of the assembly. Can you confirm that the way you are mounting them allows free air circulation around that heat sink and into the surrounding space (rather than be placed in a small space or one covered with insulation?

[Sunny Solar]

I think the problem is a lack of ventilation at the rear of lamp. Its all to easy to think of LEDs as not being heat producers like say incandescent but they do produce heat even small ones like 3w and do need adequate air flow around them especially at the rear.

[daz]

From my own experience using LED lighting, especially the LED downlights, most failures are due to heat (not enough ventilation, to small a heatsink, high ambient temps, etc). I have also noted that generally speaking, it is not always the LED chip that fails, but the actual LED driver that powers the LED chips. If you are able to open the unit up, have a look at the LED driver in the back. If you see a lot of white residue and/or a burnt 'electronic' smell, then the driver has most probably failed. If it is the driver that has failed, you could purchase the actual LED drivers themselves and just replace the faulty driver.
It may be cheaper than purchasing a totaly new unit!

[Scott594]

do the ouch test

Pick one of the lights that commonly has problems and remove the mounting hardware and then tape or prop (like with a broomstick or such) it back into the hole as it would normally be. Run you lights for a hour or 2 during the warmest normal conditions you see, the quickly power down, drop the light out, and feel the heatsink, if you can't hold your hand on it comfortably, it's too hot. Also make sure the LEDs are properly connected to the heatsink, and use thermal grease to make the connection more efficient (get the heat from the LED into the heatsink) You want the LED temperature as close to the heatsink as possible.

Usually in a series circuit, it's the LED with the highest foward drop that will fail. When replacing one, power it up on the bench and confirm forward drops with a good meter, they should be within a couple of percent.

Hope it helps.

Scott

[russ]

When I buy a LED I expect it to work - not to have to tinker with it.

[inetdog]

When I buy a LED I expect it to work - not to have to tinker with it.

I bet you would not build your own solar PV panels either.
You are taking all the fun out of it just because it is the sensible thing to do.

[justjun]

I have installed a few 5W and 9W LED down-lights in my shop ( 220V AC ).
Have been using similar lights in other locations with no issue. But here after every 10 to 12 days one the light gets OFF.
What happens is that one of the LEDs get burnt, and as all the LEDs are connected in series so the light shuts down. Then I change that one specific LED, and the light starts working again, but it happens again after another 10 days or so.
There can be number of reasons for this. Can you guide from where should I start my investigation and check out all the possible causes of this problem ?

You can change a few low voltage? 12V or 24V.