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I have a new LED ceiling light in our hall, and installed a compatible dimmer switch (both Leviton). The dimmer has a slider plus a switch, and when the switch is on, but the slider is all the way down, there is still a very small amount of light (less than most night lights, I'd say). I adjusted it as low as I could already.

I was thinking that it could be useful as a night light for the hall, but wondered if there were any dangers or problems doing this. The light is 16 watts at maximum, so I assume the power used wouldn't be very much at a very low setting.

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    I don't think there's any danger for name-brand lights (cheap, non UL-rated imported lights may not like the low duty cycle of the dimmed circuit), but you may be using more power than you needs to, I was going to do something similar, so I measured the power and found that my 11W LED still used 6W of power even when dimmed all the way (around $8/year). I bought a $5 plug-in LED nightlight instead that drew less than 1W (it registered as "0" on my meter) instead. It directed more usable light onto the floor where I wanted it, and it had a light sensor that turned off during the day. – Johnny Jan 20 '15 at 5:12
  • I think you might have the right idea. I have a nightlight already, and it's probably best to keep it. I was first worried that the new light would accidentally be left on dim, since our old light only had a dimmer to turn it on and off. I think I'll not worry about it, but try to keep it off. – Marty Fried Jan 20 '15 at 5:33
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There shouldn't be any dangers if you use a dimmer that's designed for LED lights. There are different types of dimmers for different types of lights. See this page from Lutron for a rough idea. Basically, most modern dimmers rapidly modulate between on/off and is safe for long term use in a low state. A side effect however, is that it may generate RF interference or even an audible humming sound.

In terms of danger, you might be thinking about very basic dimmers for hobby projects, which may use resistance dimming with a potentiometer. In that case, it's bad to keep it on in a dimmed state for a long period of time since it generates a lot of waste heat.

You should check this PDF (found on this page) by Leviton to see whether your specific LED light is compatible with your dimmer.

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    I'm pretty sure there are no resistive dimmers for lighting use. All dimmers work by turning the power on and off, old ones do it at 60hz, and hum. New ones do it at a higher frequency. – Ariel Jan 20 '15 at 3:29
  • @Ariel Yep, that's why I mentioned hobby projects. My science project in elementary school was a battery, a light bulb, a switch and a potentiometer dimmer :) – user193130 Jan 20 '15 at 3:31
  • Thanks for all the links; but the dimmer I got was one of the ones specifically listed on the light as being compatible (both made by Leviton), so no problem there. I just wanted to make sure it was OK in case it got left on at a low level. I guess I should assume it's safe, or they wouldn't allow it to be sold. – Marty Fried Jan 20 '15 at 5:38
  • Read the Lutron link on dimmer theory. It was interesting, although I don't understand why they used the same illustration for the sine wave's phase control for the first three types. Seems like they should be different. Still, I think it answered my questions, so I'll mark your answer as correct. Wasn't much competition, anyway. :-) – Marty Fried Jan 20 '15 at 18:15

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