Timeline for Can I safely use a 9w LED bulb in place of a 40w incandescent?
Current License: CC BY-SA 3.0
16 events
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| Apr 4, 2016 at 20:34 | comment | added | Harper - Reinstate Monica | To be more precise, the heat comes from two places: the blue LED emitter (only because we overdrive it to save money on emitters; you could underdrive it and it'd stay cool, but you'd need more emitters for the same light) ... and the the phosphors which transform blue into a spectrum of desirable light. Phosphors are inherently inefficient and fluorescents have the same problem, which is why the bulb coating is the warmest part of them. | |
| Mar 16, 2016 at 4:03 | comment | added | Nathan Osman | Well... technically the lumen measures luminous flux but I guess "brightness" conveys a similar idea. | |
| Mar 15, 2016 at 20:03 | comment | added | brhans | @SkipBerne - No. LEDs in commercial applications do not have 'current limiting resistors' - they are driven by constant-current power supplies. The bulk of the heat from the entire unit still comes from the LED itself as real LEDs are still nowhere near 100% efficient. Take a commercial LED fixture apart and you'll find its the the LED that is mounted on a big heatsink, not the driver electronics. | |
| Mar 15, 2016 at 19:40 | comment | added | Harper - Reinstate Monica | @SkipBerne here's some interesting stuff about LED efficiency. TLDR: it's a long way to 683 lm/w. en.wikipedia.org/wiki/… | |
| Mar 15, 2016 at 16:27 | comment | added | SkipBerne | The total power consumed is 9 watts, it gives off the equiv of 75 watts of light for a 75 watt incandescent bulb. . the heat generated is so low, it is only warm to the touch except for CREE bulbs .. they have not figured out how to make an LED without the current limiting resister. poor engineering. FYI an LED is a Quantum Effect Device and is near 100% efficient. | |
| Mar 15, 2016 at 13:10 | comment | added | GalacticCowboy | It's probably worth noting that the desired light output (lumens) may be a consideration too. For a reading lamp, 950 lumens may be too bright for comfortable use. Just because you can use the brighter bulb doesn't mean brighter is better. | |
| Mar 14, 2016 at 23:38 | comment | added | alexw | From what I understand, the wattage rating on bulbs is about limiting the current drawn, not the heat produced by, the bulb. Though of course there is a relationship, and OP's 9W bulb will both produce less heat and draw less current, if we want to be precise about the purpose of the ratings... | |
| Mar 14, 2016 at 20:20 | comment | added | Harper - Reinstate Monica | @BAR that is correct. Go by the actual wattage (energy consumption) of the light. | |
| Mar 14, 2016 at 20:02 | comment | added | RedGrittyBrick |
@Jim: That's not really right. The meaning of 9W=75W is that the LED lightbulb consumes only 9W of electric power to produce the same light output (luminous flux) as would be produced by a 75W tungsten-filament incandescent lightbulb. I find it best to use lumens to compare lightbulb brightness.
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| Mar 14, 2016 at 19:56 | comment | added | BAR | So it can handle a 9W bulb because the lamp is rated to dissipate up to 40W of heat energy, but you wouldn't want to install an old-style 75W as the lamp could overheat? | |
| Mar 14, 2016 at 19:48 | comment | added | Shimon Rura |
@Jim technically the 9W=75W means it has output similar to a 75W-consuming incandescent, but consumes only 9W. The wattage is how much power the bulb consumes. Bulbs consume electric power and emit heat and light; more efficient bulbs emit a higher proportion of light and less heat. The wattage rating on a fixture typically reflects how much heat it can safely tolerate.
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| Mar 14, 2016 at 18:48 | history | edited | Harper - Reinstate Monica | CC BY-SA 3.0 |
clarity
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| Mar 14, 2016 at 18:46 | comment | added | Aaron | The problem is that lightbulbs used to be measured in popular parlance by wattage (energy), not by light output (lumens) So people went shopping for a 100W bulb not knowing how much light output they were looking for. Since nowadays we have CFL and LED lamps that produce the same amount of light on much less wattage, they helpfully tell you what the equivalence is for the light, in this case a 9W using (energy) will produce the same amount of light as a 75W conventional bulb | |
| Mar 14, 2016 at 18:45 | history | edited | Harper - Reinstate Monica | CC BY-SA 3.0 |
added 507 characters in body
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| Mar 14, 2016 at 18:43 | comment | added | Jim |
So the meaning of 9W=75W is that is has "power" of 75W but makes only 9W?
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| Mar 14, 2016 at 18:39 | history | answered | Harper - Reinstate Monica | CC BY-SA 3.0 |