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I looked at this question which seemed to be the closest to resemble my situation, but it's just not a close enough case.

I have a bunch of ceiling lights that are MR16 20W Halogens. I've replaced two of them with 6W (power) 50W (equivalent lumens) bulbs. They're fine for thirty minutes or so. Then they go dark. I haven't watched to see if they go out simultaneously. But by the time I return to the kitchen to check, they're both out. Turning off the switch, waiting a second or two and turning them back on and they're lit again.

What is causing this and how do I fix it?

Bob Kaufman
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1 Answers1

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Something with a time delay like that is usually thermal.

The heat of the halogens is killing the LEDs

Halogens want to burn very hot. They are deliriously happy inside ovens. They wouldn't even mind lighting up a steel mill ladle. I'm told junction temp on a halogen is 2000C.

LEDs do not like heat. You own a screw-in light bulb product based on LED technology. It has an electronic driver and heat sinks. Deep inside it is LED emitters proper, they are much smaller than a fingernail. They need to stay under 85C, even though they're making about 5.5W of heat. That means there needs to be heatsinking/heatpiping to carry heat away. Thermal movement down a heat sink is proportional to the difference in temperature. So that heat sink must be significantly cooler than 85C or else the heat won't move away from the LED emitters fast enough, and they will be destroyed.

You have one LED screw-in product in an enclosure or ceiling space containing a bunch of halogens. The ceiling space might not get up to 85C, but it doesn't have to; the heat sink will be defeated well before that. I imagine these products have a temp sensor on the LED or heatsink, and are shutting down to prevent the LED from incinerating itself.

The way to test this for sure is unscrew all the halogens and run the LEDs alone. If it stays stable, that was it.

Harper - Reinstate Monica
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  • This sounds like the most reasonable answer I can imagine. I am going to replace the other eleven halogens with LED's this afternoon and will report back with my results. Thank you – Bob Kaufman Dec 21 '19 at 18:28
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    @BobKaufman I would just unscrew the halogens for now and make sure you've cleared the problem. If so, then proceed. – Harper - Reinstate Monica Dec 21 '19 at 18:29
  • I'm still stumped. In said kitchen, there's also a couple of "singles" the same kind of can light over the sink and over the back door. So I can turn on just one light and leave the rest of the ceiling dark. I've replaced both of those and they, too, go dark after about half an hour. I'm taking a different approach and getting a sample of a different LED can light assembly altogether. They're only five bucks each so I'm willing to risk the purchase – Bob Kaufman Dec 26 '19 at 16:05
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    $5? Uh oh. This might be a case of cheap junk. Are thesr items sold at retail stores, or do rhey have a UL, ETL, or CSA listing with file number? – Harper - Reinstate Monica Dec 26 '19 at 16:15
  • good point. They were towards the cheap end of what I found on Amazon that matched my requirements (4" diameter, 2700-3000K, 50W effective). I will find something a little more trustworthy. – Bob Kaufman Dec 28 '19 at 16:54
  • @BobKaufman Amazon, eh? Could be Amazon Marketplace, read my spotter's guide here... "the world's biggest flea market" as I've called it... Buying from Marketplace is the equivalent of buying from a street seller in Bangkok. – Harper - Reinstate Monica Dec 28 '19 at 19:15