Fixture socket say only use led equivalent to 75watt incandescent

[jaggedben]

Yes, but the driver components have to be cooled by conduction into the base. Someone likely calculated the thermal conductivity, expected maximum ambient temperature, and then decided how hot they wanted it to get.

I willing to be shown this for real, but I'm still a bit skeptical. Some amount of the heat and IR from incandescent is conducted into the base as well, and some amount of the heat from an LED can be radiated into the air instead of the base. And the former is still very large compared to the latter. (I've seem some LED bulbs with fins that look like their supposed to radiate into the air, and many without.) I suppose that specifying an equivalent lumen LED may be a way of accounting for being unable to control the LED bulbs design and efficiency. So it's CYA. What I doubt that they did the calculation you describe and coincidentally came up with the the 'equivalent' (in lumens) LED bulb.

 

[marmathsen]

I've run into issues where the physical size of a higher wattage bulb doesn't fit. For example a 9w (60w eq) is an A19 but a 100W eq is an A21 and won't fit in the fixture.

I had to explain to the client, "I guess I was wrong, as it turns out, you CAN'T put a 15W LED bulb in there"

I just looked though and it does appear that there are A19 100W eq bulbs now.

Rob G

 

[marmathsen]

This conversation makes me wonder, do multi-lamp fixtures ever state that you need to or should either install all LED lamps or none at all? I've never seen it. But it seems reasonable that if you had 2 incandescent lamps generating a lot of heat and one LED that couldn't handle the heat, that would be problematic, it at least annoying when the LED constantly fails.

Rob G

 

[GoldDigger]

I willing to be shown this for real, but I'm still a bit skeptical. Some amount of the heat and IR from incandescent is conducted into the base as well, and some amount of the heat from an LED can be radiated into the air instead of the base. And the former is still very large compared to the latter. (I've seem some LED bulbs with fins that look like their supposed to radiate into the air, and many without.) I suppose that specifying an equivalent lumen LED may be a way of accounting for being unable to control the LED bulbs design and efficiency. So it's CYA. What I doubt that they did the calculation you describe and coincidentally came up with the the 'equivalent' (in lumens) LED bulb.

As a gross simplification, whatever the heat dissipation mechanism to get heat entirely out of an enclosed fixture, operating at a lower maximum temperature (because of driver electronics and LEDs) will require a lower operating power.
What leaves the fixture as visible light is, of course, not a problem.

 

[gadfly56]

I willing to be shown this for real, but I'm still a bit skeptical. Some amount of the heat and IR from incandescent is conducted into the base as well, and some amount of the heat from an LED can be radiated into the air instead of the base. And the former is still very large compared to the latter. (I've seem some LED bulbs with fins that look like their supposed to radiate into the air, and many without.) I suppose that specifying an equivalent lumen LED may be a way of accounting for being unable to control the LED bulbs design and efficiency. So it's CYA. What I doubt that they did the calculation you describe and coincidentally came up with the the 'equivalent' (in lumens) LED bulb.

Why do you doubt that? If they hadn't, there would likely be no max LED wattage on the package. I can't imagine it's all that hard if you have the tools. And incandescents really don't care how hot they get, as long as you don't exceed the socket listing, not having any electronic components and all.

 

[jaggedben]

Why do you doubt that? ...

Again, that the number they came up with is coincidentally the same lumen equivalent. Because actually doing any testing or calculations would likely come up with something different.

 

[jaggedben]

As a gross simplification, whatever the heat dissipation mechanism to get heat entirely out of an enclosed fixture, operating at a lower maximum temperature (because of driver electronics and LEDs) will require a lower operating power.
What leaves the fixture as visible light is, of course, not a problem.

While I see your point, the fixture manufacturer's responsibility is primarily to the safety of the fixture and not the longevity of the bulb.

The more I think about it, the more I don't see how the fixture manufacturer can specify an LED wattage based on anything other than a standard that references incandescents. Perhaps the minimum standard for LED bulbs simply specifies that they not raise the fixture temp higher than the equivalent incandescent? That would make as much sense.

Again, I'm happy to be enlightened about how the industry handles this. I'm just skeptical, from experience as well as theory, that the typical actual LED bulb raises the fixture temp as much as an equivalent incandescent. (At least for screw type bases, for the experience part.)

 

[wwhitney]

Again, that the number they came up with is coincidentally the same lumen equivalent. Because actually doing any testing or calculations would likely come up with something different.

If they came up with an answer that's within 10% of the same, for consumer labeling it would just make sense to use the same value.

Also, if consumers blame the fixture when LED bulbs in it fail, and leave bad reviews or whatever, it behooves the fixture manufacturer to provide a warning label about not putting in LED bulbs that may be likely to have a short life, even if the fixture itself would not be overheated by them.

Cheers, Wayne

 

[jaggedben]

As a data point, I just went and unscrewed the '60W equivalent' LED from the bathroom sconce after it had been left on for at least 10mins. With my bare hand. Without turning it off. Typical GE A19. The part above the base that holds the driver was a bit hotter than I wanted to keep touching but not hot enough to burn. The screw base and outer bulb were barely warm. Try that with a 60W incandescent. You'll either want gloves or need to turn it off first.

 

[jaggedben]

If they came up with an answer that's within 10% of the same, for consumer labeling it would just make sense to use the same value.

Also, if consumers blame the fixture when LED bulbs in it fail, and leave bad reviews or whatever, it behooves the fixture manufacturer to provide a warning label about not putting in LED bulbs that may be likely to have a short life, even if the fixture itself would not be overheated by them.

Cheers, Wayne

So you're agreeing with me. It's not a decision based primarily on engineering calculations of what (actual) wattage LED bulb the fixture can safely withstand.

 

[wwhitney]

So you're agreeing with me. It's not a decision based primarily on engineering calculations of what (actual) wattage LED bulb the fixture can safely withstand.

I agree that it's not the above. It may be based on an engineering calculation of what actual wattage LED bulb is likely to work long term in the fixture. Or it may have little engineering content.

Cheers, Wayne

 

[AC\DC]

The Consciences is that if its an open bulb fixture, they should not have that limitation, It would only apply to bulbs Enclosed in fixture. Correct?

 

[James L]

The Consciences is that if its an open bulb fixture, they should not have that limitation, It would only apply to bulbs Enclosed in fixture. Correct?

I would think so

 

[hbiss]

Again, that the number they came up with is coincidentally the same lumen equivalent. Because actually doing any testing or calculations would likely come up with something different.

My thought is that if a 75 watt equivalent LED generates the same amount of heat as a an 75 W incandescent where is the savings?

As a data point, I just went and unscrewed the '60W equivalent' LED from the bathroom sconce after it had been left on for at least 10mins. With my bare hand. Without turning it off. Typical GE A19. The part above the base that holds the driver was a bit hotter than I wanted to keep touching but not hot enough to burn. The screw base and outer bulb were barely warm. Try that with a 60W incandescent. You'll either want gloves or need to turn it off first.

My observation also.

The only reason I can come up with is that LED fixture manufacturers just include that BS information to cover their butts. As for lamp longevity, has anybody actually opened a bulb to see how it's constructed? Typically there is a round PC board disk right about where the frosted part meats the opaque "neck". There are LED chips surface mounted around the PC board with probably the cheapest electrolytics and other components used in the driver. Usually one or more LED chips fail or the electrolytics fail due to high temperatures within the bulb. These bulbs CAN be made to last a very long time (longer that incandescents as they advertise) with premium components but the manufacturers wouldn't make any money that way.

So LEDs are just another cheap Chinese product that I wouldn't expect much from.

-Hal

 

[Another C10]

It might not be about the wattage, it might be about the heat generated.

I'm pretty sure a 75w incandescent environment gets much hotter than a 75w Led anything.

 

[tallgirl]

So you're agreeing with me. It's not a decision based primarily on engineering calculations of what (actual) wattage LED bulb the fixture can safely withstand.

It's not what the fixture can withstand, which may be completely insane, but what the BULB can tolerate, in that fixture.

The temperature where most people instinctively pull back their hand when they touch something is 135-140F. If you ran an LED at that temperature its life expectancy will go down quite a bit.

 

[gadfly56]

I'm pretty sure a 75w incandescent environment gets much hotter than a 75w Led anything.

It's all about the temperature the driver electronics are subject to. So I can see a fixture that will accommodate a 75 watt incandescent lamp not being able to support anything over 23 watts for an LED (as an example).

 

[hbiss]

It's all about the temperature the driver electronics are subject to.

And my opinion is that that temperature is dependent on the design of the bulb more than anything else. I think that even an A lamp LED in a jelly jar type fixture wouldn't make much difference.

-Hal

 

[jaggedben]

It's not what the fixture can withstand, which may be completely insane, but what the BULB can tolerate, in that fixture.

The temperature where most people instinctively pull back their hand when they touch something is 135-140F. If you ran an LED at that temperature its life expectancy will go down quite a bit.

It's all about the temperature the driver electronics are subject to. So I can see a fixture that will accommodate a 75 watt incandescent lamp not being able to support anything over 23 watts for an LED (as an example).

Like Hal said, the fixture manufacturer doesn't know whose bulb is gonna be used, so they can't really test for that. And LED bulb designs vary in ways incandescents I assume dont. Makes more sense for an LED bulb to be labeled e.g. 'Suitable for use in fixtures rated for xxW or higher incandescent' than vice versa. Such a label on a bulb would, for me, override any label like the one the OP described on a fixture. I still wager the fixture label is just CYA.

Again, I'm happy to be enlightened about what standards say. Seems like everyone on this thread is just guessing though.

 

[tallgirl]

Like Hal said, the fixture manufacturer doesn't know whose bulb is gonna be used, so they can't really test for that. And LED bulb designs vary in ways incandescents I assume dont. Makes more sense for an LED bulb to be labeled e.g. 'Suitable for use in fixtures rated for xxW or higher incandescent' than vice versa. Such a label on a bulb would, for me, override any label like the one the OP described on a fixture. I still wager the fixture label is just CYA.

Again, I'm happy to be enlightened about what standards say. Seems like everyone on this thread is just guessing though.

I don't have access to a proper FLIR camera on a regular basis, but I suspect the majority of the heat is conducted out the base these days. I've not seen many medium base bulbs with any kind of heat sink in ages. I could point my IR thermometer at various parts of a bulb, but I can't point it INSIDE the lamp holder, which is what I suspect matters the most.