I'm replacing my old recessed lighting by retrofitting them with LEDs. I'm using a Lutron Diva DVCL-153P dimmer switch to control these recessed lights, but when set at low dim levels, flipping the switch results in a 3-5 second delay before power on. I've tried several different LED models now with varying results:

  • Sunco DL_BFDR56-13W-27K (very short delay but significant flicker)
  • Halo LT560WH6930R (very long delay)
  • Feit Electric LEDR56B (short delay)

I assume that this delay is caused by the LED driver waiting for the dimmer capacitors. Is there any possibility that the dimmer switch is the culprit? It's supposedly compatible with the Halo and Feit lights according to the Lutron website.

This is the best resource I've read to understand all these nuances. https://www.manufacturer.lighting/info/190/

  • 1
    I agree, it's the LEDs waiting for the capacitors to charge up. You are using a legacy dimming method called "triac", which was a way to make dimmers cheap and run cool, at the expense of chopping up the AC sine wave beyond recognition. LEDs basically see it as dirty power or a brownout. Dimmable LEDs analyze the chopped sine wave to figure out what the dimmer is trying to say, but it can only do that after it acquires its wits, which requires a full capacitor. The right answer is better dimming tech. PWM or 0-10V. But PWM is DC and 0-10V is commercial. Commented Nov 7, 2021 at 3:03

1 Answer 1


IMPE, it's virtually guaranteed that the dimmer is the cause.

I opted to get LED dimmers, because the LED units I got were dimmable.

"Why not?"

The nasty bits not mentioned: include does not go to full brightness, at least 1/2 second perceptible delay (at full brightness) with my dimmer/lights combination (.vs. normal instant with a normal switch) and for one set of lights a highly annoying noise (not present with a normal switch.) If you care about such things, also destroys the power factor (switched LEDS 99 or better, dimmer on full power, I forget but lousy, like 57.)

I left one in one position, I removed the others and replaced with normal switches. The last one still irritates me with the delay to turn on and may yet get replaced. It's the dimmer taking time to power up and get on the job, from what I've seen - not the LED drivers.

  • Blaming a dimmed light for poor power factor is rather unfair. Power Factor is defined by how much the actually drawn current differs from a pure sine wave. Now look at a triac dimmer waveform! No load has a chance at a good PF when the delivered "sine wave" looks like Yosemite. Commented Nov 7, 2021 at 3:07
  • No. The dimmer, set to full brightness (should be, but obviously is not, bypassed) has terrible power factor. The lights have great PF. Teriible PF when dimmed, I expect. Terrible PF at "full" brightness is bad dimmer design.
    – Ecnerwal
    Commented Nov 7, 2021 at 13:28
  • @Ecnerwal, you're saying the dimmer capacitor is the culprit and not the LED driver capacitor? If it's the dimmer, are there any solutions available for a home? I was unaware both components had them. Excuse my lack of knowledge.
    – Higgy
    Commented Nov 7, 2021 at 15:34
  • @Higgy I doubt dimmers have capacitors. (outside of the tiny one in the 555 circuit, but that's command/control and doesn't interact with the line). The issue is actually more complex than capacitors. Commented Nov 7, 2021 at 18:46
  • Yeah what you're expecting out of a "full on" dimmer is bypass. I had a dimmer that had a bypass at the bottom turning it off entirely (many do) but also a bypass at the top giving full power (few do, might be a UL reason for that). You had to push it past a stiff detent to get there. It's a deluxe feature you would need to pay for. Commented Nov 7, 2021 at 18:50

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