Blue 2-1 Dimmer and Hue Bulb Buzzing

Switches Wiring Discussion
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Hey all, I’ve reviewed some previous threads on this, and I haven’t been able to nail down anything that addresses my specific issue, so I’m posting here in the hopes someone might be able to help me solve the issue. In my basement I have a Blue 2-in-1 dimmer wired to 6 pot lights with Philipps Hue BR30 bulbs in them. This particular wiring configuration is a 2-1, non-neutral setup, with the switch being controlled in Home Assistant using Z2MQTT and configured as a “single pole” setup and set to “smart bulb” mode. I’ve got the bulbs also visible in Z2MQTT and bound to the switch.

What I’ve found is that when the lights are on, both the switch and the lights emit an audible hum. As I dim the bulbs, the buzzing reduces, and as I increase the brightness, the buzzing because more noticeable (see video). I’ve tried configuring the switch using both leading-edge and trailing edge per some of the other posts in the forums, but that hasn’t helped me. I also previously chatted with support, and they added two things:

  1. Try swapping out the Hue bulbs for incandescents and see if the buzzing stops. I didn’t have 6 incandescents, but I did remove all the Hue bulbs and just put one incandescent in and didn’t experience any buzzing.
  2. They mentioned I may need a bypass. Has anyone else experienced this buzzing and found bypasses actually solved the solution? It seems like these need to be wired at the fixture, which means each of the 6 pot lights. Is that correct? Can someone explain more about why this would help?

Just looking for some clarity here. I have an electrician I’ve worked with in the past, so if it boils down to a wiring thing that’s fine, but I’m worried that without a little more information to help him out, this is more of a “technical” problem than an “electrician” one, so I’m just looking for some specificity to say “Hey, I need this and this to stop this,” etc.

P.S. I don’t currently have any additional Blue switches to test whether this is isolated to this switch or if this occurs in other places. Hoping to get some soon when the next wave starts shipping.

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As a first step, I would pull the switch to ensure that all three conductors are firmly attached. You should be able to tug on them fairly hard and not have them come out. A loose conductor can cause an issue.

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Thanks, Bryan. I forgot to mention two things:

  1. I did check the installation of the switch and actually trimmed the ground because it was preventing the switch from getting all the way in the box
  2. I swapped the line and load lines because they were not color-coded in any way (just white), and using a pen tester, both appeared to be live. I’m not sure how common that is.
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Did you test both conductors with them removed from the switch? Both of them should not be hot. One should be hot. The other, which goes back to the light, should not be.

What type of wiring do you have, Romex or individual conductors in conduit?

Both of the conductors are white???

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Apologies, I was mistaken on both counts:

  1. The wires were not white, they were black. Here’s a photo.
  2. Also, I went back and retested the wires following your comment. I think the wires were too close when I originally tested them, because in that picture, the wire on the right is hot and the wire on the left is not hot when the breaker is on, so I made sure the wire on right is in the “line” terminal on the switch. Removing and rechecking these things did not change the buzzing.
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That sure looks like an available neutral in the switch box… What is your reasoning for not using it?

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It wasn’t used in the previous switch, and if those 2 white wires are both neutrals, because both were wire-nutted together, I wasn’t sure what the best course of action was. Is this a fairly typical situation?

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Outside of a couple very rare exceptions, dumb switches/dimmers don’t use neutrals, so they wouldn’t have one connected.

It is common to have neutrals junction in a switch box, since it’s often just simply a convenient junction point.

The requirement to have a neutral available in a switch box is relatively new, so many older houses don’t not have neutrals available at the switch.

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What @hydro311 said. That is not a non-neutral.

Pigtail of white wire to the neutral terminal of the switch. The black that is hot goes to the line. The black that is not hot goes to the load.

Yes, that is exactly how it is done in a neutral environment.

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Gah, in other words, I should have just read the manual. Thank you both for the support and for again pointing me to the appropriate resources.

Is it expected that with a neutral, that buzzing will stop, or is getting this wired using a neutral just the next step in a troubleshooting?

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Maybe? Probably? Without knowing more about the buzz cause, no one can say for certain.

Never pass up an available neutral. Whether or not it solves the buzzing issue, you should use the neutral. Using a neutral is always the preferred option vs not using one.

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Understood. I just purchased some wire since I know I’ll be doing this for all of my switches and will very likely be encountering this again, so I’ll make sure anything I wire up in the future uses a neutral when possible.

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The Blues and Reds all come with a neutral pigtail, so unless those got tossed, there should be no need to buy add’l wire.

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Great call. I forgot about that. Did toss that particular pigtail, but had some romex lying around, so I wired it up with a neutral. Now the switch reports power consumption (yay!), and the buzzing does appear less audible. I also toggled between leading edge and trailing edge and trailing edge definitely also reduces the buzzing to almost non-existent.

So, moral of the story for my situation was:

  • RTFM
  • Use your neutral if you have it
  • Set to Trailing edge
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