What happened to this LED bulb?

[pete6032]

Pulled this bulb on the right out of a standard ceiling mount "boob" light after it started flickering. Replacement bulb on left for comparison. The other two bulbs in light were not flickering but I noticed they were hot at the bases, like close to incandescent warm. I don't think LEDs are supposed to do that so what's the process for diagnosis?

 

[Paperdoc]

There is some misunderstanding about LED bulbs. Many "understand" that they make no heat. WRONG!They DO make much less waste heat than an older incandescent bulb for the same light output, as evidenced by the WATTS rating. For the same light as a 100W incandescent bulb, an LED bulb typically uses about 15W. That's only about 15%. HOWEVER, in BOTH types of lamps a LARGE fraction of that power is actually HEAT released into the surroundings. For an incandescent, the heat is over 95% of the Watts consumed; in an LED that fraction is much smaller. But the LED still does generate some heat. Why? That is mostly in the DRIVER circuit, a small electronic circuit built into the BASE of the lamp that converts the typical 120 VAC power supply to about 5 VDC that the LED elements require. A small amount of heat is actually generated in the LED elements, but not much.

This also means that WHERE the heat is has changed. ALL the waste heat from an incandescent bulb is generated at the filament in the middle of the globe, so the BASE of the bulb gets warm simply by conduction of heat from the glass envelope to the base. In a LED bulb the main heat source is IN the base portion, so most of the waste heat is concentrated there. That is why the photo from OP shows discolouration of the base portion of the lamp.

This has an impact on the wattage rating of the LED lamp you can install in a light fixture. Any fixture has a rating for the max WATTS of lamp you can install, and that is based mostly on the ability of that fixture's base to dissipate heat and to withstand the temperature it operates at. Both the lamp socket material and the insulation of the wires to that socket are factors. The rating of the fixture is based on those factors when you use an incadescent bulb that generates a lot of heat. If you use an LED instead there is much LESS heat to deal with (it is using only 15% of the Watts), and hence you can afford to use a LED lamp that puts out MORE light than the comparable incandescent lamp, and uses more than that low wattage. HOWEVER, you can NOT use an LED lamp that consumes 100 W power and puts out 7 times the light! MOST of the heat from the LED lamp is concentrated in the SOCKET area, so the socket's ability to dissipate that heat into the surroundings is the limiting factor. What IS the LED lamp limit for such a light fixture, since the label rating is created for an incandescent lamp? I have never seen any guideline for this, and I don't know how it can be generated. What does appear, though, is that you CAN use a modest upgrade of LED lamp output. For example, I have no qualms using an LED rated to be "equivalent" in light output to what a 200 W incandescent lamp can do, in a fixture rated for use with a "100 W" incandecent.

 

[WilliamM2]

Even a 9 watt LED will overheat in a 100 watt fixture if it's in a completely enclosed fixture(no air flow), new bulb looks like a 9 watt there.

The LED bulb needs to be rated for enclosed fixtures. It says something about "enclosed" on the dark bulb, but I can't read it all.
I have several bulbs that say they are NOT rated for enclosed fixtures.

 

[Paperdoc]

You are quite right. Enclosed fixtures retain heat much more, so for the SAME types of component materials they are rated for LESS max lamp power. Moreover, many such are designed with the lamp socket at the TOP of the fixture (e.g. ceiling fixtures), concentrating the heat even more at that socket. The combination of these two factors plus the location of the heat source in an LED lamp does mean you need to be careful how such lamps are use. But IF the lamp fixture IS rated for, say, a 100W incandecent lamp, there should be no problem using in it an LED of equivalent light output (15 W), and maybe a bit higher.

 

[WilliamM2]

But IF the lamp fixture IS rated for, say, a 100W incandecent lamp, there should be no problem using in it an LED of equivalent light output (15 W), and maybe a bit higher.

Not true. I used a 9watt LED (60 watt equivalent) in a 100 watt rated enclosure. The bulb overheated and died . Discolored just like the bulb in the OP. No damage to the fixture.

That's why they rate some bulbs for use in enclusers. I didn't notice the small print on mine that said NOT rated for completely enclosed fixture. First time I left the light on for a couple hours, it died. I've also heard of this causing a small fire, or melting the socket.

 

[Paperdoc]

Very interesting story! Anyone else with similar results?

 

[WilliamM2]

Very interesting story! Anyone else with similar results?

Story? There are two with those results right in this thread.

Can LED Lights Be Used in Enclosed Fixtures? - LED & Lighting Info

So who else wants to replace their old school bulbs with some sweet, energy-saving LED ones? Some of you have already been there and are enjoying the savings in your energy bills. And some are thinking about it and looking for the right place to start. It definitely seems like it's a simple...

ledlightinginfo.com

 

[Paperdoc]

Thanks for the link to that article. Very useful.

 

[shortylickens]

 

[BoomerD]

The heat issue is (at least partly) why oven lights and most microwave light bulbs aren't LED.

Can LED Bulbs Be Used In Ovens? - LED & Lighting Info

While replacing your fixture and home lights with an LED is more or less straightforward and almost always the better option to go with when it comes to appliances. In this case, gas or electric ovens, an LED is not going to work. The ideal bulb to use in ovens is the traditional halogen or

ledlightinginfo.com

 

[Red Squirrel]

Part of the issue is lot of them have a plastic base which does not dissipate heat well. I have Ecosmart bulbs that constantly go on and off and stopped buying that brand. I think it's a combination of defect (cold solder joint probably) and heat. I did notice the base gets very hot that you can barely touch it. They probably use very shitty circuits for the power conversion instead of a proper constant current SMPS.

 

[pete6032]

Part of the issue is lot of them have a plastic base which does not dissipate heat well. I have Ecosmart bulbs that constantly go on and off and stopped buying that brand. I think it's a combination of defect (cold solder joint probably) and heat. I did notice the base gets very hot that you can barely touch it. They probably use very shitty circuits for the power conversion instead of a proper constant current SMPS.

Pretty sure Ecosmart is about 90% of the shelf at Home Depot. That's what I bought to replace the other bulbs. I don't have any more flickering but I haven't checked to see if these ecosmart bulbs have any burn-in after a few weeks of use yet.

 

[gorobei]

the edison socket kinda needs to be retired. the hurdles and workarounds for dimmer switches/smarthome for LED bulbs is nightmarish.

a better socket with better heat sinks would let you move the power conversion circuitry off the bulb where there is no room for a decent heatsink. you could also build in PWM for dimming control into the socket rather than trying to do it with wifi (more junk in the confined volume of the bulb)

just make the led module replaceable, put the driver circuits in the socket(also replaceable), and make less fixtures that have to be thrown out when one part fails and you cant access it because they are all glued together.


and yes led bulbs get hot. i cant imagine the buck converter in there is using the best mosfets for the lowside switch. for the mass production numbers and commodity cost ceiling they have to be pinching pennies on the mosfet/heatsink.

 

[Red Squirrel]

I kind of like how fluorescent fixtures do it. The ballast does the conversion and is replaceable, and the bulb has no electronics and is also replaceable. The fixture itself is basically just metal with no electronics whatsoever as serves as the housing.

I think a similar approach needs to be done but for screw in light bulbs. Have a small user replaceable ballast module that is part of the fixture and is standardized in size and output, and the bulb is basically just a string of LEDs inside and has little to no electronics. Also they need to stop making fixtures with built in LEDs, that is the stupidest concept ever. Both the driver and bulb should be replaceable and standard.

 

[WilliamM2]

Sounds like a lot of fun replacing the dozens of fixtures in my house and garage. No thanks.

They need to just make all bulbs suitable for enclosures. May cost a little more, but will be much cheaper than replacing all the fixtures, especially for the average home owner that would need to hire an elecrician.