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Camelot One
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join:2001-11-21
Bloomington, IN

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[Green Tech] Troubleshooting a buzzing LED - all LEDs, in one fixture

I have 4 can lights in the theater room. They are wired up with power coming in to an Insteon dimmer: »www.smarthome.com/switch ··· ite.html
which then runs out to a dual rocker single pole switch:
»www.homedepot.com/p/Levi ··· 02027000
From there I have separate lines running to the first light in each row, and then to the second. (global dimmer but with the option to turn off each row independently)

My issue is that the first light in row 1 buzzes. Not a high pitch, more like the old florescent fixtures when I was a kid. It is noticeable when they are on all the way, and louder when being dimmed, though it is a constant level at any dimming amount. I started with Philips LEDs: »www.homedepot.com/p/Phil ··· 05395637
I can move the bulbs around to different fixtures, and no matter which bulb is there, it is still row 1, light 1 that buzzes. If I remove that bulb, the 2nd light in that row does not start buzzing. If I turn off the rocker for row 1, row 2 does not start buzzing. I also tried putting a Cree bulb in that one: »www.homedepot.com/p/Cree ··· 04366182 with the same result.

Everything I have found online points to some LED models buzzing, some dimmer and bulb combos buzzing, or bad dimmers causing buzzing. But in each case, it is all of them, not just one. So without knowing what problem I am trying to find, I am not sure where to start troubleshooting.

Any suggestions?

tschmidt
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[Green Tech] Re: Troubleshooting a buzzing LED - all LEDs, in one fixture

Due to the way dimmers operate they change the AC waveform. One thing to try is to temporally bypass the dimmer to verify it is an actually an interaction between the dimmer and bulb.

Since the buzz always occurs at the same fixture it is probably a combination of bulb noise and fixture resonance. Be worthwhile seeing if you can do anything to add additional stiffness to the fixture.

/tom

nunya
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The dimmer switch you referenced is only rated for incandescent loads (No LED or CFL). That's probably the noise source. Are you sure it's the lamp and not the switch buzzing? Are they near each other?

Also, make sure some knucklehead didn't connect the switch neutral to the ground conductor. I see people do that all the time with all this X10 and insteon stuff to try and cheat it in. Neutrals weren't required in switch loops until recently, so many switch boxes have no neutral available.

It's hit or miss with dimmable LED and CFL lamps. I've had them work in old dimmers just fine. Other times, the buzzing is so outrageous that an LED rated dimmer is required.
My own office is a prime example. If I use a mixture of dimmable LED and regular light bulbs on the same older dimmer switch, the standard bulbs "sing" (filaments vibrate). If I use only LED or only incandescent, everything is fine. Go figure.

Camelot One
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Bloomington, IN

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said by nunya:

The dimmer switch you referenced is only rated for incandescent loads (No LED or CFL). That's probably the noise source.

I didn't catch that. I just assumed a current model, $50 dimmer was rated for LED/CFL. Looking over the insteon site, I don't see that listed on any of their devices.
said by nunya:

Are you sure it's the lamp and not the switch buzzing? Are they near each other?

Positive. The first light is about 5' from the switch, but the buzzing is loud enough that it is easy to track the source to the light.
said by nunya:

Also, make sure some knucklehead didn't connect the switch neutral to the ground conductor.

I was the knucklehead doing the install, and it was a new wire job. I pulled it out to make sure, but everything is wired correctly at the switch. And yes, these require wiring the neutral.
said by nunya:

It's hit or miss with dimmable LED and CFL lamps. I've had them work in old dimmers just fine. Other times, the buzzing is so outrageous that an LED rated dimmer is required.
My own office is a prime example. If I use a mixture of dimmable LED and regular light bulbs on the same older dimmer switch, the standard bulbs "sing" (filaments vibrate). If I use only LED or only incandescent, everything is fine. Go figure.

I may try playing around with mixing LED and incandescent bulbs on that row and see what happens.

Next up is pulling the switch to see if I get buzzing when the lights are direct wired.

Msradell
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join:2008-12-25
Louisville, KY

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Just as another point of reference, I'm using a pressure Insteon wall-mounted dimmer with LED bulbs and do not have any noise problems. Not saying your problem isn't the dimmer but it's not inherent in the design of Insteon dimmers.
HarryH3
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Since the problem doesn't move with the bulb, perhaps the can itself is the problem. There may be a piece of tin in the can that just happens to vibrate at just the frequency of the a/c hum. To check, see if you can kill the noise by touching different parts of the inside of the can with a long dowel or plastic rod while the light is on.

Thespis
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Re: [Green Tech] Troubleshooting a buzzing LED - all LEDs, in one fixture

Have you tried replacing with a high wattage incandescent? I've heard dimmers buzz with a small load and fixed the problem by attaching a "dummy load" in an unseen location.

Camelot One
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Re: [Green Tech] Re: Troubleshooting a buzzing LED - all LEDs, in one fixture

said by tschmidt:

Since the buzz always occurs at the same fixture it is probably a combination of bulb noise and fixture resonance. Be worthwhile seeing if you can do anything to add additional stiffness to the fixture.

/tom

You may be on to something. I took the trim off and let the socket just hang rather than being clipped to the housing, and the buzzing almost went away. Enough that I can livr with it. So I will try rrplacing the clip on the socket and see how it goes.