Dimmers for LEDs: Not up to the job yet?
June 3, 2017 5:48 PM   Subscribe

I have a mix of LEDs and incandescent bulbs. The LEDs don't dim well; while the incandescents will evenly dim down to almost nothing, the LEDs are stuck at about 50%. I asked an electrician about replacing the dimmers with those made for LEDs. He told me that even current dimmers made for LEDs don't all the way to 0W, and to properly dim, I need a new fixture for each bulb and a new dimmer. Is that correct?

According to him, LED dimmers (like the Lutron DVLVs) still won't go below 40W, and 40W is ample power for, say, 8 LED bulbs.

He seemed to know his stuff, and he was not proposing to swap out all my fixtures -- he was telling me why I shouldn't try to do it until the tech catches up.

Are there dimmers out there now that will dim LED bulbs down all the way? Has anyone installed LED dimmers that bring the light all the way down?

I'm using Phillips Warm Glow dimmable LED bulbs, which also bring the color temperature down to get that cozy low-light look. But they don't dim all the way with my current setup.
posted by musofire to Home & Garden (13 answers total)
My understanding is that there's a cutoff voltage below which a LED just won't operate. I don't know if it's a fundamental principle of LED's, or if it's just a property of current LED control circuits.
posted by Huffy Puffy at 6:06 PM on June 3, 2017

I've got Lutron Caseta dimmers and they work just fine to dim LEDs. In fact, you can customize how low they dim and they can get very, very, very dim.
posted by noneuclidean at 6:08 PM on June 3, 2017 [2 favorites]

Oh, and I should add that I did not swap out any fixtures when I added the dimmers, and all are using run-of-the-mill LED bulbs (i.e., whatever is cheap at Home Depot).
posted by noneuclidean at 6:11 PM on June 3, 2017

Not all LEDs are dimmable. Do you know if yours are? If they are, you can toggle the dim range on the side of a Lutron dimmer (have to remove the face plate and pull it out of the box)
posted by walkinginsunshine at 7:33 PM on June 3, 2017

Your electrician claiming that there are LED-specific fixtures is enough to concern me that you should, perhaps, get a new electrician. Assuming we're just talking about screw-in LED bulbs, there's no possible reason I can think of that you'd need a new fixture. You do need to "tune" the dimmer switches, but I've had no problem getting my LED bulbs quite dim.
posted by Betelgeuse at 7:50 PM on June 3, 2017 [1 favorite]

I'm using LEDs on a dimmer that is really really old and it works just fine, they dim to almost nothing on the low end.

I read somewhere that you can't have incandescent and LED on the same dimmer circuit, and even different brands of LEDs on the same circuit can give not-optimal results.
posted by slagheap at 10:29 PM on June 3, 2017

The house I grew up in has two fixtures with dimmable LEDs. In both of them, they can dim down to about candlelight-level brightness, but I've noticed that as they are dimmed, they begin to emit a buzzing noise that becomes louder until they are dimmed completely.
posted by The Pluto Gangsta at 5:49 AM on June 4, 2017

Response by poster: They are Philips Warm Glow 9.5W, model 455832 (https://www.homedepot.ca/en/home/p.led-95w--60w-a-line-a19-warm-glow-2700k--2200k.1000826952.html). What is the difference between forward phase and reverse phase, and how would I be able to tell what I have?
posted by musofire at 7:22 AM on June 4, 2017

Response by poster: One of the dimmers is theoretically for LEDs (a Leviton Sureslide Cat No. 6674), the others are Seymour 600W dimmers for incandescents, 105-220-3.
posted by musofire at 7:37 AM on June 4, 2017

Best answer: Incandescent dimmers are typically straight unfiltered leading-edge (SCR / triac) dimmers because they're really inexpensive to make. They basically make the voltage the bulb sees look like the red line on this graph. That sharp rising voltage spike makes CFL and LED power supplies (generally) very very sad: they don't act like the big resistors that incandescent lamps do. Result: cranky lights that dim poorly, have high dim cut-off, flicker, and die an early death due to poor current in-rush management.

A good modern dimmer will solve your problems.

(Random notes: It's possible to make SCR/triac dimmers that don't suck but they require extra parts on the output and so old-school incandescent dimmers don't. LED-friendly dimmers are set up to meter the one thing LEDs care about: current.)
posted by introp at 6:37 PM on June 4, 2017

Response by poster: So here's what I've found:

a. You need LED dimmers. Regular ole dimmers don't go down far enough.
b. You need all LED bulbs; having incandescents on the same circuit seems to throw everything off
c. You need all the same make and model LED bulbs! Different make/model bulbs seem to throw things off as well
d. Although I did not test this, possibly not all LED bulbs dim down all the way. Two bulbs I've found that work are the Philips Warm Glow 10w (60w) A19s (regular clear bulbs) and Philips Soft White Par20 mini floods.
posted by musofire at 7:12 AM on June 14, 2017

I would say your first and third premises are false: like I said above, I grew up in a house where we have dimmer switches that were originally installed for normal incandescent bulbs. We have LEDs in all the fixtures now and the old dimmers work fine. We can dim the LEDs down to about a candle-light level brightness and the only unusual thing is that keeping them dim makes a small buzzing noise.

In one of the fixtures we have a mix of 2 different kinds of LEDs, and it doesn't interfere with the functioning. However, if you're a stickler for them being the exact same color and shade of light throughout, then yes, you should make sure they're all the same.
posted by The Pluto Gangsta at 4:16 PM on June 14, 2017

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