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I have read numerous dimmer switch instructions say compatible with led lights and then also led bulbs saying dimmable. So my question is do only the bulb and switch need to be compatible or does the light fixture itself impact compatibility too and should say if dimmable compatible?

I ask this because my ceiling fan currently has older non-led bulbs and I upgraded to LED bulbs. Now I am thinking of adding a LED dimmable switch but I am curious if the fixture itself needs to be dimmable compatible or not.

Also when two devices are not compatible say led bulbs with non led compatible switch then what happens (potential fire or overheating of dimmer?). I have some old dimmers in this house and the led bulbs seem to work fine but I’m sure these are pretty led dimmers so I’m surprised it worked.

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Not normally, no.

But ceiling fans, yes. Because ceiling fans typically insert one of two troublemakers:

  • A current limiter, to prevent you from over-bulbing the light with 100W incandescent bulbs when they're only approved for 25/40/60W
  • A "remote control module" so you can use a wireless remote to control fan and light.

Both of them might play badly with LEDs, and both of them may well play badly with dimmers on LED. They were never designed with LED in mind.

And by "LEDs" I mean lightbulb replacement units with LED technology and an Edison screw base, along with an electronic driver to convert 120VAC into DC to run the LED emitters.

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It depends on how your fan is wired. If you only have 1 switch to turn your fan on and off you can not put a dimmer on that switch.

If you have 2 switches one for the lights and 1 for the fan, though, then usually you can install the dimmable LED’s with the proper LED compatible dimmer.

I have done this a few times for customers and not had problems with current limiters but I haven’t done every type of fixture that has limiters.

To tell the truth if the limiter was an issue I would look into bypassing it. The limiters are there to reduce the wattage being drawn and were mandated by the Department of Energy back in 2005, but with LED’s, you will never reach that wattage limit of 190w without being blinded by the amount of light.

Not all ceiling fans have limiters on their lights, but if they do and it is causing problems, there are many Youtube videos on how to remove them. Just remember that the wiring was designed for 190w max to all the lamps combined.

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It depends. All LED bulbs run on low voltage DC current. That means that 120v AC must be converted to that type of current and level of voltage. This is accomplished by a LED driver that converts the 120v to usable current for the LED. Many LED bulbs today don't need an external driver since they make the proper conversion internally, but some still do.
Read the literature on the bulbs you are buying. It should tell you if (a) the bulb is dimmable and (b) if it needs an external driver and the specs for that driver.
So as long as you're purchasing LEDs that don't requre an external driver you should be okay. But in my experience matching dimmers and LEDs can often be hit and miss with how well they work. In some combinations you may get flickering or other nuisance effects. It's not dangerous when it happens, only annoying.

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  • So incompatibility by the users selection has no hazards other than poor performance? Jan 31 at 3:45

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