If I have a ceiling light fixture that's rated for 60 watts incandescent could I safely put in a LED that would be rated as 75 watts?
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If I have a ceiling light fixture that's rated for 60 watts incandescent could I safely put in a LED that would be rated as 75 watts?
Is the LED a 75 watt LED or a 75 watt equivalent. Since folks know what a 75 watt incandescent bulb produces in terms of light the manufacturers have used "75 watt equivalent" terminology. The actual current draw is 13 watt on a randomly picked 75 watt bulb on Home Depot's website. Proper way to compare light output is lumens not watts. The two things to look at our actual current and heat produced. The power consumed is not all converted to light. For these two hypothetical "75 watt equivalent" bulbs (and incandescent at 75 watt total power consumption and a 13 watt LED ("75 watt equivalent light output") at least 62 watts are dissipated as heat (actually more since the efficiency of the LED is not 100%). So the LED will draw less current than the Incandescent (even the 60 watt) and will generate less heat.Quote:
Originally Posted by Jerry Bruette
As to what the code allows, I don't know. I am guessing (and only guessing) the code is based on actual wattage.
John
The actual wattage of the lamp is what matters. A 75watt equivalent LED is about 12 watts. You do need to pay attention to things like "wet/outdoor rated", "dimmable", or "enclosed fixture rated". Some LED bulbs do get hot.
On a closed fixture, I would not "over watt" the lamp. LED's still put off a lot of heat. I just measure the temperature on the base of a 3 way LED bulb that has been on for several hours in an open fixture and it measure 154 degrees F. The bulb is rated at 25 watts at the high level.
I'd consider what it might do to insurance payout if for some other reason there was a fire. Might/could void coverage if it was uncovered, saying wrong size bulb.. Brian
Yes. Vast numbers of fixtures like that have had 75w incandescent lamps in them, & LEDs put out much less heat than those.
It's a conservative, legalistic warning.
The primary reason for the wattage ratings in light fixtures is based on heating from what was the incandescent light bulbs - nothing at all to do with light output.
So if you buy a bulb they like to tout in big letters on the box as a 75 watt bulb it very, very likely puts out the amount of light (lumens) that a 75W incandescent would have put out.
You have to look at how much power the LED consumes and it will be probably about 15-20% of the 75W rating. This smaller amount of heat is all you have to worry about for the fixture ratings. Now, the other problem you have to worry about is whether or not the LED lamp is rated for totally enclosed fixtures. As was pointed out, the bulbs (usually the bases) can get very hot which is due to the driver electronics and, of course, heat is bad for electronics so enclosing the bulb when it shouldn't be will cause a premature failure due to above rated heating. BTW, heat can shorten the life of the actual LEDs too and also can cause their rated light output to drop over time.
On a couple of outdoor fixtures I have drilled some holes in fixture base to allow airflow, there was a little gap at the top already. No problems and this has been a few years.
I've never seen an LED bulb that had the "equivalent" wattage printed on the bulb itself, rather than just on the packaging.Quote:
Originally Posted by Brian Runau
LED's put out about a third of the heat, so if a fixture is rated at75w, then I would feel very comfortable putting a 100w LED equivalent, which is about 14 watts.
The wattage rating is there for heat purposes, as some older fixtures had paper insulators which got a little crisp with anything over about 60 watts incandescent.
I wouldn’t hesitate to put just about any wattage of LED that will fit into that fixture. That said, cheap LED bulbs die of heat. I have hundreds, perhaps over a thousand to tend to at work, and I’m still occasionally pulling out a dead CFL that was installed before I started 8.5 years ago. However, I’m also replacing LED bulbs that I installed less than a year prior at times. I write a date on every bulb when I install it. We quit buying one brand of bulb from our supplier.
Anyway, for the most part, the dead LEDs I’ve pulled all had plastic bases that turned yellow or brown and then cracked from the heat.
And, as another friend pointed out to me a few years ago: all LEDs use circuitry to run—find a capacitor rated for more than about 4,000 hours. The actual LEDs (the diodes themselves) can easily last 50,000 or 100,000 hours (unless over-drived), but capacitors don’t tend to have such a lifespan, especially not as a component of a bulb manufactured to a price point.
I like the extra light I can get from upsizing LED over CFL or incandescent, but I’ve soured on the longevity claims. Now compare the manufacturing processes and components of incandescents and LEDs, and ask yourself if they really are all that much greener if they end up in a landfill after not much more use.
It will probably be just fine.Quote:
Originally Posted by Jerry Bruette
The wattage rating of a light fixture is based on a multiple things: Ampacity of the conductors, physical space available, and the ability to deal with the heat that's generated by an incandescent bulb. Of additional concern is the impact of the heat on the light lens material (if a lens is present).
You don't say what kind of fixture you have (open, enclosed, surface mount, recessed, etc.) but it was tested as part of its UL listing for the intended installation.
I used to manufacture light fixtures. The one most relevant to this inquiry was a recessed lighted bathroom fan. It was tested and listed to a 60 watt maximum bulb capacity. Part of the testing involved installing the product in an insulation filled test fixture (we called it the hot box), fitted with a thermocouple array, and left on for a prolonged period. The temperature of all the surfaces was monitored, and was subject to limitations in order to pass the test. Consideration was also given to the impact on the thermoplastic lens in terms of discoloration, distortion, and potential for ignition. Once we achieved our rating, we incorporated a barrier to prevent a physically larger 100W bulb from being able to be installed. This barrier approach is very common in enclosed fixtures. It's as much of a risk mitigator as anything.
With the advent of the government deciding what kind of light bulbs we should use, the old rating system of bulbs is pretty much out the window. While the size, shape, and base style codes for bulbs are still used; performance ratings are now in Lumens. The old 60 watt bulb size (A19 if I recall) is now available with a Lumen rating up to the equivalent of a 100 watt incandescent bulb. This performance comes without the same level energy use or of heat generation. It will also fit where the old 100 watt size wouldn't. Another plus is that the light spectrum generated is often "whiter" and perceived as brighter. Some perceive this as harsher.
All that and $5.00 will get you a cup of coffee at Starbucks. I've never seen any sort of study that speaks to the heat issue. CFL and LED lights do produce heat. It is less than an incandescent, but less is a relative term. I will say that in my bathroom fan (Broan/NuTone), I have installed a brighter LED bulb (100 watt equiv. in Lumen ratings) with no ill effects. It fits just fine and when I made the switch it didn't seem to generate nearly as much heat. Ampacity of conductors was not an issue. I prefer the brighter light.
What matters is real watts used. An incandescent bulb is a very efficient heater, almost all of the energy going into it is converted to heat, only a trivial percentage coms out as visible light. So that's the worst case scenario.
A 10-20 watt LED, no matter what the packaging says it is the "equivalent" of, can make no more than 10-20 watts worth of heat. It's not a heat pump, and it's not a magical device able to pull energy out of the ether to make more heat than the input power can be converted to.
I agree with Rob and Roger's posts above.
However, while the incandescent bulb heating was a concern for the fixture's components and surrounding structure rather than the bulb itself this isn't the case for LEDs. The "not for enclosed fixtures" warning is to prevent the LED's components overheating since this is where most of the heat is generated in a small volume. As usual, heat shortens electronic components life.
Of course, the real question is whether or not a particular enclosed fixture, such as a large one, is quite alright for the heat dissipation.
Some of those old paper insulators could get a bit crispy even with a bulb of 60 watts or less over time.Quote:
The wattage rating is there for heat purposes, as some older fixtures had paper insulators which got a little crisp with anything over about 60 watts incandescent.
jtk
When overlamping with incandescent lamps it was possible to damage the wiring in the J-box behind the fixture, even more of a problem with older NM sheathed cable with TW insulation, which ceased being manufactured in the mid 1980's.