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When looking at light switches I noticed that some have a built in dimmer slider like the one pictured below and I have two related questions about them.

Is there any concerns with replacing a normal light switch with one like that?

And when it comes to replacing the bulbs with LED versions will I need to ensure that the dimmer is LED compatible? (Yes, I understand the LED itself needs to be dimmable or it will have issues) And if that is the case how would I determine if an existing switch like that is LED compatible?

As a side note if I was to update the switches in my house to work with dimmers and or be more smart enabled is there a style that would be best for that goal?

As a note the house was built in 2009 so while it is newer it may or may not have the required neutral that was later built into code.

Light Switch with Dimmer

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  • Usually the other way with LEDs. The LEDs need to be dimmer also.
    – crip659
    Jan 8, 2023 at 20:02
  • With LED, the LED has to be the dimmable type
    – Traveler
    Jan 8, 2023 at 20:04
  • @crip659 If you mean you need a LED light bulb that is rated to be dimmable I understand that and will update the question. What I was more referring to is will any dimmer switch work with a dimmable light bulb or do I need to make sure it is compatible?
    – Joe W
    Jan 8, 2023 at 20:05
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    You have to check the specific dimmer. Most made today will specifically list if they are LED compatible, though some specifically are not. And even then, unless you find a list specifically showing compatibility between switch A and light B, there is no real guarantee. Smart-enabled gets much more complicated, primarily because most require a neutral in the switch box, which may or may not be available, especially in older buildings. Jan 8, 2023 at 20:12
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    @JoeW The requirement was added in NEC 2011, so it didn't apply to your house when built. Which doesn't mean you don't have neutrals in switch boxes, but it means you might have some switch boxes without neutrals. Ignoring grounds, if you open a single switch box and find at least 4 wires including 2 whites connected together then you have neutrals. If you have only 2 or 3 wires you almost definitely don't have neutral. But YMMV. Jan 8, 2023 at 20:25

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Is there any concerns with replacing a normal light switch with one like that?

Yes, you need to make sure it isn't powering a receptacle (dimming a receptacle is quite dangerous), and then you need to make sure that the wires which the dimmer needs are available in the light switch box. Not all are - there are several ways to wire light switches.

As a note the house was built in 2009 so while it is newer it may or may not have the required ground that was later built into code.

Neutral is not the same thing as ground. It should have ground (which is nothing but an emergency fault catcher and should never flow current normally)... but the question is whether it has neutral (the normal route for return current). Abuse of ground as neutral makes it worse than no ground because it can energize all the grounds on that circuit!

The requirement for neutral at switch locations arrived in NEC 2011, so your house is a little old to be assured that.

And when it comes to replacing the bulbs with LED versions will I need to ensure that the dimmer is LED compatible?

Dimming in AC power is a black art. Variacs and resistors are not practical, so they use a cheap but ugly technology called triac dimming to modify the AC waveform. This works reasonably well with incandescent bulbs but tends to be extremely hit-and-miss with LEDs. Basically the LED has to try to extract enough power to function (from the broken AC sinewave), then analyze the AC waveform to try to figure out what the dimmer is trying to do, and then control the LED to that brightness using current-control or PWM. It's a Rube Goldberg hack.

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    Thanks for the answer, I have updated my question based on this because I made a mistake in updating my question based on a comment that was left for me.
    – Joe W
    Jan 8, 2023 at 23:49
  • Even variac dimmers would be no good at dimming LEDs... Jan 9, 2023 at 1:28

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