LED bulb

J

JDB3

Senior Member
Location
San Antonio, Texas
Been a while since I have been on here. Was talking to a man today, that said he had bought a package of LED bulbs & put them in an enclosed fixture. Later he read on the box that they were not to be used in an "enclosed" fixture. Do that make LED bulbs with this warning? Is this because these particular LED bulbs put out more heat (for some reason) ? Thanks for replies
 
Little Bill said:
You need to look for ones that say they can go in enclosed fixtures.
Click to expand...
I have no idea why they are allowed to sell bulbs that cannot be used in enclosed fixtures. The purchaser shouldn't have to look at the package fine print to find that.

Furthermore, I've questioned this whole thing about not being for use in enclosed fixtures as to why. They don't get hot, none of them do. Certainly not like an incandescent. So really, I believe it's just a recommendation that cautions the user that using a particular bulb in an enclosed fixture MAY shorten the lifespan because the manufacturer uses bottom of the barrel components (like electrolytics) to keep the cost low.

-Hal
 
I always assumed it just meant a shorter life than advertised if used in an enclosure. In my personal experience I've put many in enclosures and some were rated that way and some not.
 
hbiss said:
I have no idea why they are allowed to sell bulbs that cannot be used in enclosed fixtures. The purchaser shouldn't have to look at the package fine print to find that.

Furthermore, I've questioned this whole thing about not being for use in enclosed fixtures as to why. They don't get hot, none of them do. Certainly not like an incandescent. So really, I believe it's just a recommendation that cautions the user that using a particular bulb in an enclosed fixture MAY shorten the lifespan because the manufacturer uses bottom of the barrel components (like electrolytics) to keep the cost low.

-Hal
Click to expand...
The base of the LED bulbs do get hot (some anyway) and they are almost too hot to handle. All the electronics are there and that's the fail point. I have seen some that were enclosed and did fail.
 
Little Bill said:
The base of the LED bulbs do get hot (some anyway) and they are almost too hot to handle. All the electronics are there and that's the fail point.
Click to expand...

If that's the case, then it would be the heat sinking ability or thermal mass of the socket the bulb is screwed into that would conduct the heat and dissipate it away. Air trapped in the fixture would have little effect unless the socket had heat sink fins.

-Hal
 
hbiss said:
If that's the case, then it would be the heat sinking ability or thermal mass of the socket the bulb is screwed into that would conduct the heat and dissipate it away. Air trapped in the fixture would have little effect unless the socket had heat sink fins.

-Hal
Click to expand...
But light sockets in luminaires and other light fixtures are not generally designed to serve as heat sinks. They used to be designed to withstand the temperatures of incandescent bulb bases, not to conduct heat away.
By their very nature, incandescent bulbs had no components that could be adversely affected by temperatures as high as 100C. No consumer electronics components which are affordable for use in LED bulbs can withstand that sort of temperature.
And the heat rejection of the electronic ballast circuitry typically located in the base of an LED bulb is generally dependent on air circulation, and surrounding air temperatures reasonably close to ambient temperatures. In an enclosed fixture you might have neither.
 
GoldDigger said:
And the heat rejection of the electronic ballast circuitry typically located in the base of an LED bulb is generally dependent on air circulation, and surrounding air temperatures reasonably close to ambient temperatures. In an enclosed fixture you might have neither.
Click to expand...

I doubt very much that there would be an appreciable difference in air circulation either way. It all goes back to making a decent product with a reasonable lifespan. Not using the cheapest components and design possible to make more money then put fine print on the box about not using it in an enclosed fixture as an excuse when it burns out after a few weeks. But what do you expect from China?

-Hal
 
tthh said:
I always assumed it just meant a shorter life than advertised if used in an enclosure. In my personal experience I've put many in enclosures and some were rated that way and some not.
Click to expand...
It does mean a shorter life, I don't think it "just" means that.

They have all those electronics rated to withstand a certain temperature for a certain number of hours.

That involves wattage, ambient temperature, etc.

You might see something where it's rated for an ambient temperature of 99° and it'll say it will run 15,000 hours.

It may be something like 8.3 watt bulb. And you can pretty much be guaranteed that those components in there are 8.2 watt capable.

But if you put that into an enclosed exterior fixture and it gets up to 105° outside, The ambient might be as high as 125° and then you might see the life go all the way down 1500 hours or less
 
Watt for watt, LEDs put out the most amount of conducted heat than any other light sources.
The heat from a 25W incandescent bulb is mostly put out as infrared. Some of this escapes the luminaire as radiated heat while much of it is absorbed by the globe and the entire surface of globe exchanges heat with the surrounding environment.

Incandescent lamps and HIDs dispose very few watts as conducted heat. What doesn't get released as visible light is projected as infrared light.

A hermetically sealed industrial computer for use in dusty environment uses a circulation fan and finned case. The fan is needed to carry the heat from CPU to case, because CPU can not tolerate getting hot enough to radiate away heat. An incandescent lamp of the same wattage as the CPU would transfer the heat to the case through radiant energy, so it can do without a fan.

A radiant heat source like incandescent lamps have no problem being islanded. Things like microprocessors and LEDs don't like being islanded. The difference between an LED luminaire and a screw-in luminaire is that LED elements' can be thermally bonded to the base of the fixture and conduct heat away. That's why 60W incandescent enclosed fixture doesn't mean it can handle a 60W LED.
 
Situations are different for continuous use LED vs those that only needs to stay on for a few minutes per hour. Many LED stuff (flashlights, security lights, bulbs..) often utilizes LED element fry out protection which is essentially a thermostat which controls the wattage going into LED elements to maintain a constant heatsink temperature once the threshold temperature is reached. It's kind of like hot plate. You power it up and the heater stays on, then it cycles on and off to maintain the temperature. Since "on and off" isn't reasonable for lighting, dimming ballast is activated and reduces LED wattage to maintain the heat sink temperature.

Something that's often omitted in spec sheet of high output LED screw in bulbs is that they're often unable to perform at rated output for more than a few minutes. The inherent limit in LED bulbs mean that they either operate at full output to a certain temperature and become a lower output bulb for most of the running time, or the elements and/or the ballast burns out. This is deceptive for continuous duty lighting, however it's fine for lights that normally only operate a few minutes at a time. This can be tested prior to a large scale deployment by placing a sample LED fixture in a small jelly jar fixture and operating it continuously inside a covered bucket (to simulate high ambient) while monitoring input wattage.

A smaller power lamp (40W equivalent/4W input or so) can often handle continuous operation at rated output. Larger lamps like 1600 lumen/100W equiv will dim down or fry out, even if rated "totally enclosed". Unfortunately, they often fail to disclose that it can not maintain full output while in a sealed fixture.
 
Last edited:
Flicker Index said:
Watt for watt, LEDs put out the most amount of conducted heat than any other light sources.
The heat from a 25W incandescent bulb is mostly put out as infrared. Some of this escapes the luminaire as radiated heat while much of it is absorbed by the globe and the entire surface of globe exchanges heat with the surrounding environment.

Incandescent lamps and HIDs dispose very few watts as conducted heat. What doesn't get released as visible light is projected as infrared light.

A hermetically sealed industrial computer for use in dusty environment uses a circulation fan and finned case. The fan is needed to carry the heat from CPU to case, because CPU can not tolerate getting hot enough to radiate away heat. An incandescent lamp of the same wattage as the CPU would transfer the heat to the case through radiant energy, so it can do without a fan.

A radiant heat source like incandescent lamps have no problem being islanded. Things like microprocessors and LEDs don't like being islanded. The difference between an LED luminaire and a screw-in luminaire is that LED elements' can be thermally bonded to the base of the fixture and conduct heat away. That's why 60W incandescent enclosed fixture doesn't mean it can handle a 60W LED.
Click to expand...
It seems you're trying to compare a 25w I can to a 25w LED, and then compare a 60w I can to a 60w LED only on the basis of heat per watt 🤔

That's disingenuous, and you know it.

A 60w LED bulb most likely isn't even going to fit inside a fixture meant to enclose a 60w incandescent bulb. And you know that, too.

It's okay to say "my biased opinion is that LEDs suck"

It's not okay to talk in circles, then try to pretend it's a genuine scientific position which sprung from concern for the lighting industry 🤦
 
Bes, thanks!

It is plausible that a 60W LED bulb will have more conducted heat than a 60W incandescent bulb, because the incandescent will radiate so much waste heat.

I suspect that if you compare bulbs of the same lumen output, the LED bulb will have less conducted heat, because so much less total power is needed to produce the same amount of visible light.

The LED bulb will be more temperature sensitive and so will suffer more if the heat conduction is poor, even if the temperature is lower.

Jonathan
 
Some LED bulbs come with a warning about using them in enclosed fixtures. This is because LEDs, while generally cooler than incandescent bulbs, are more sensitive to heat. Enclosed fixtures can trap heat, causing the LEDs to overheat and potentially shorten their lifespan or reduce their efficiency.

All in all, LED bulbs do get hot, but they don't produce a lot of heat, If you're interested, Here are reference articles related to :
Understanding LED Heat Generation

Lumens (lm)Incandescent Watts (W)LED Watts (W)Energy Savings (%)
450404-588-90
800608-1083-87
11007510-1382-87
160010013-1684-87
260015025-2882-83
300020030-3285-85
 
winnie said:
Bes, thanks!

It is plausible that a 60W LED bulb will have more conducted heat than a 60W incandescent bulb, because the incandescent will radiate so much waste heat.

I suspect that if you compare bulbs of the same lumen output, the LED bulb will have less conducted heat, because so much less total power is needed to produce the same amount of visible light.

The LED bulb will be more temperature sensitive and so will suffer more if the heat conduction is poor, even if the temperature is lower.

Jonathan
Click to expand...
I was simply explaining why fixtures may say "60W incandescent" but how a 17W 100w filament equivalent LED may not survive in it.
60W filament lamp gets rid of most of the heat by infrared, which is radiated out, or absorbed in the reflector. The reflector in turn gets blistering hot.

A 17W LED lamp may put out maybe 5W of visible spectrum, but the other 12W has to go somewhere and much of that has to be conducted away the heatsink.

The amount of heat rejected by a fialment bulb as conducted heat is in single digit %.
 
You must log in or register to reply here.
Top