Fan "Bounce" When Off

I’m finally getting into setting up my home and am hoping to deck out my home with the blue series switches, but have run into something very strange on my first fan switch.

I wired the switch with a neutral in the box and paired it to my home assistant setup with no issues - I previously installed a blue 2-1 switch next to it.

Shortly after the install I noticed something that I thought was a ‘drip’ noise at night. The next day, I realized it was coming from the fan. About every two seconds, the fan “Ticks” or “Bounces” despite the switch being turned off. This behavior vanishes when pulling the air gap.

I have tried factory resetting and made sure that it was set to single-pole and exhaust fan modes.

Any suggestions? I’m scratching my head at this one. The fan is a slow start, so I’m wondering if the switch is leaking enough energy to slighty charge whatever circuitry is in the fan and cause this? Everything runs fine otherwise.

Video: PXL_20231207_214747906.TS.mp4 - Google Drive
Picture: PXL_20231207_214705643~2.jpg - Google Drive

Thanks in advance.

That fan has a DC motor, so that may be part of the problem. The blue fan switch officially does not support DC motors.

That being said, there are users that have been using the blue fan switch with DC motor exhaust fans without an issue. However, there are other users that have been having issues using the blue fan switch with DC motors exhaust fans. IIRC, these were all Panasonic Whisper variants.

The other reported issues related to getting the fan to either start or run. You are the first that has posted about the “drip” issue.

Inovelli has sent a DC motor exhaust fan to the manufacturer for analysis. So they may have some answers regarding the DC motor exhaust fans sooner or later.

Bry - Good catch. This afternoon was actually the first time I pulled the cover off to look at it. I’m surprised the builder paid extra to put that atrocity in.

I started reading up on the model I have and it looks like it converts the AC to DC in order to vary the CFM and it has some on-board electronics that explain the poor functionality I was blaming on the switch it was on previously. For a ‘humidity sensing’ fan, it sure did have a tendency to turn off while I was in the shower rather than speed up like it should.

I just put an order out to get an AC version that should be able to swap in with minimal effort (same cutout, etc.) and will try that out over the weekend when it arrives.

I’m still very curious as to what is happening in my video. I’m new to these switches, but wouldn’t expect them to let enough power past to do anything to the fan circuit beyond. Unfortunately, I don’t have access to an oscilloscope anymore, sounds like it would be interesting to analyze.

It’s MOSFETs switching capacitors on and off so, yes, it’s likely leaking some power to the fan motor until it tries to start.

You’ll most likely will find voltage if you check with a multimeter.

I’ll see what I can find out when I do the fan replacement in a few days. I doubt I’ll take the switches out for measurement, but the suggestions all make sense.

If anything, I’m still surprised that the builder splurged on a DC fan, but it may have ticked some checkbox on requirements that I’m not aware of. Definitely worth ‘downgrading’ the smart fan to a smart switch either way.