Another LED indoor light thread - how much heat?

[newbury]

The prices for 60W A19 style bulbs finally dropped below my pain point, and I've couple of ceiling bulbs to replace so I bought a two pack for $4 at Lowes .

Based on prior experience I expected them to be a little brighter than the bulbs I was replacing. Wrong - a lot brighter.

Which brings up the question - How much LED can I stuff in a "can" light from the 1970's designed for 65 watt incandescent?

I've got a few fixtures designed for a 65 watt BR 30 (about 500 lumens) and am thinking of replacing them with LED's. And if the prices drop I'd like to put in 13 watt BR 30 LED's WHICH ARE 100 WATT EQUIVALENTS, a lot brighter.

Will that be safe?

 

[k0ua]

The prices for 60W A19 style bulbs finally dropped below my pain point, and I've couple of ceiling bulbs to replace so I bought a two pack for $4 at Lowes .

Based on prior experience I expected them to be a little brighter than the bulbs I was replacing. Wrong - a lot brighter.

Which brings up the question - How much LED can I stuff in a "can" light from the 1970's designed for 65 watt incandescent?

I've got a few fixtures designed for a 65 watt BR 30 (about 500 lumens) and am thinking of replacing them with LED's. And if the prices drop I'd like to put in 13 watt BR 30 LED's WHICH ARE 100 WATT EQUIVALENTS, a lot brighter.

Will that be safe?

I would think so.
Consider that on an incandescent lamp I believe the efficiency is about 5 percent. So 5 percent of that 65 watts is light and 95 percent is heat. So it follows that .95x65= 61.75 watts of heat.. So if you are sticking in a 13 watt device That is way more efficient to begin with.. I am thinking your fixture is not going to overheat.

 

[Raspy]

100 Watt equivalent LEDs means it puts out the same amount of light as a 100 watt incandescent. But LEDs use about 13 watts to do it. Watts is a measurement of electrical energy, but it's also a reasonable measurement of the heat output. With incandescents, about 95% of the energy going into the bulb becomes heat. So about 95 watts of heat is produced from a 100 watt bulb. LEDs do get warm, but they cannot produce more than 13 watts of heat even if all the energy went to heat and none to light.

LEDs are safer in light fixtures because they run way cooler. They are much more durable and much more resistant to breakage.

Remember, 100 watt equivalent only means a comparison of light output from two bulbs, not how much heat they produce or how much energy they use. It's a very poor way to compare the two because it leads to confusion about energy used and therefore, cost.

When you are looking at the cost, remember also that LEDs are only using about 13% of the energy for a given light output. And they should last much longer. That factors in VERY favorably even at a higher initial cost. It's hard to realize that 95% (!) of a standard light bulb's energy use, is doing nothing more than producing heat, not visible light.

 

[SPIKER]

yes LEDs run cooler when used in car headlights the mfg puts in heating elements to clear snow off lenses. What Raspy said about wattage is good run of thumb.

M

 

[ultrarunner]

Growing up as a kid I got a nasty burn from a pole lamp with a metal shroud... it had a 75W bulb.

Mom still has the same pole lamp only now it has a 60W CREE LED and the metal shroud doesn't even get warm.

 

[dstig1]

There is a quirk with LEDs vs incandescents that I saw a great article about a few years back... and just found it after a pretty extensive search. It is worth a read as it explains it much better than I was about to do... There is more heat generated from LEDs than you think. Not as much total as from incandescents, but it has a major impact on the LEDs.

http://www.em.avnet.com/en-us/design/marketsolutions/Documents/Lighting/LightSpeed-Eskow-0508.pdf

 

[Raspy]

In LEDs, like incandescents, brightness depends on the drive voltage. I ran a number of experiments with them comparing voltage to lifespan. At about 2 volts, the LEDS were OK for a long life. Lower and they were dimmer, but any higher, like 2.2 and they lasted only a couple weeks. 2.7 volts would take them out in hours. Of course a lot has to do with cooling. So, in this age of cost and brightness demands, they must be driven hard, but not too hard. The wild claims of extremely long life bulbs, I'm afraid, are speculative and not always accurate. I've had a number of them fail already, while others have run continuously for years.

The power converter in flashlights may use as much or more power than the LEDs. I find the power circuits can get hotter than the LEDs. Also, LEDs can be wired in series to reduce each one's voltage from the source. It seems to me that a more efficient power source, compared to the way it seems to be done, would be to just add as many LEDs in series as needed to get their voltage to about 2 volts each. This might be about 60 that run on a 120 volt circuit, after the diode.

The end color is a factor in this too. In order to get the desired "cool" vs "warm" average from a "bulb", there is a mix of various color LEDs and each color has it's own lumens per watt efficicncy. It's a very complicated and interesting field. And LEDs have to simulate the color of incandescents to be accepted in homes.

Since LEDs only know how to produce one wavelength of light, when dimmed, they just produce less of the same color with no yellowing.

So much of what is done is designed to make the differences between incandescent and LEDs become invisible to the human eye. It's a time of transition in lighting and so many people are resistant to anything new, even if it is better. I've heard all the excuses as to why people don't want an LED light in their home. Pretty comical, if not sad, but definitely human. A person will complain about their electric bill and refuse to cut their lighting energy to about 13% of what is is now because it's a new technology. Or even more silly, if they suspect a person with a different political persuasion like them, that's it, no way will they try them.

 

[k0ua]

I can tell you this much, I am a very right wing conservative, and I am Converting to LED as fast as funds will allow. It makes good business sense. The ROI was not good upon introduction of the technology, but it does now.

 

[newbury]

There is a quirk with LEDs vs incandescents that I saw a great article about a few years back... and just found it after a pretty extensive search. It is worth a read as it explains it much better than I was about to do... There is more heat generated from LEDs than you think. Not as much total as from incandescents, but it has a major impact on the LEDs.

http://www.em.avnet.com/en-us/design/marketsolutions/Documents/Lighting/LightSpeed-Eskow-0508.pdf

Good link. I think I had read links like that saying "LED's run hotter" and that is why I was concerned.

But I decided a little "red neck" testing would answer my question.
I've got a track light setup that uses 60W bulbs.
In one I placed the 60W equivalent LED, in the other a 60W equivalent CFL. After running for a few hours my HF $25 Ir thermometer measured 89 deg F on the back of the LED unit and 91 deg F on the back of the CFL unit. Cool.

 

[tractchores]

I have replaced all my old ceining 'can' lights with LED's. I went with brighter LED's than the incandecents. The LEDS are cool enough I can unscrew them after they've been on, so they are prodicing WAY less heat than the old ones. its a great way to get more light in a house where they were conservative on the number of recessed light fixtures. I always felt like my recessed lights got really hot too, which was a major consideration for a switch to LED's a couple of years ago. So far so good...

 

[ultrarunner]

I have not made the change in Olympia where I have a lot of recessed lighting and a lot of lighting overall.

In winter... leaving 4 75W canned lights on made the roomer warmer... thinking this will not be the case when I switch.

The change will have to wait for when/if I move back.

 

[techman]

What the article did not elaborate is that a majority of the infrared from and incandescent bulb ends up heating the area surrounding the bulb. If you note, only 8% of the energy ends up as visible light, compared to 25% for an LED. Greatly reduced radiant heating with an LED is the largest factor of reduced heating. As a comparison LED = 75% of 13 watts, or about 9 watts of heat. Incandescent = 75% of 100 watts is about 75 watts of heat. The LED is about 1/8 of the total heat. So yes they are safe in a can.

paul

 

[Raspy]

tech,

I can't make those numbers work. I have some 60 watt "equivalent" LEDs here to compare with incandescents.

If 8% of 60 watts (4.8 watts) = a number of lumens from a 60 watt incandescent. How can a 60 watt "equivalent" LED produce the same number of lumens with 25% of 8.5 watts? That equals .25 X 8.5 watts = 2.125 watts. Less than half the watts. It seems the visible light per watt numbers don't work as the watts used by the LED per lumen is about half based on 8% and 25% numbers for watts per visible light, or lumens.

Is there a discrepancy in the power supply between different manufacturers? Are they not really equivalent? Or are my numbers way off?

Interestingly, I have two 60 watt equivalent LEDs here. One uses 8.5 watts and the other 10 watts. Cree has just introduced a new bulb that appears WAY cheaper to make. But I don't have the figures on it's performance.

 

[dragoneggs]

LED 'bulbs' are now designed to passively dissipate heat decently enough to cover the their output. For normal household applications you don't need a fan. Active cooling of LED's becomes necessary when you start concentrating light such as for a reef aquarium or other needs requiring high PAR lighting.