I was trying to find some resources talking about how different is the Smart Fan Switch from regular Smart Dimmer, but the only thing I’m finding is warnings to not use Smart Dimmer for fans as it’s dangerous.
I am pretty well-versed in electronics and I understand differences in controlling motors vs. lights on AC and some challenges related to motors. However, to my knowledge shaded pole motors as used in most bathroom fans cannot be speed-controlled without a VFD or to a point with voltage-only control. Thus, any bathroom fan will be controlled in a on-off manner anyway.
Can a Smart Dimmer set to SwitchType=Single-Pole Full Sine Wave and OutputMode=On/Off be used for controlling a shaded-pole motor safely, or is there some additional consideration like possible arcing in the relay that Smart Fan Controller solves?
I didn’t check with my oscilloscope (yet?) but others confirmed that in the full sine wave mode the output seems 1:1 with input.
Even in the on/off mode, it’s still a dimmer and that’s not rated for motor loads. That was not the original intent during development, but that’s how it worked out.
The On/off switch, which is a true relay based switch, should be available shortly
Thank you for reply Bry. If I remember correctly, during the initial phase it was planned for the 2-in-1 to be able to control a fan but it was dropped partially due to UL listing. I fully get that Inovelli cannot advertise it as such even if it happened to work.
Would you be able to shed some technical light, if it’s not a secret, on the reason why Smart Fan Switch is able to control a motor but a Smart Dimmer (even in On/Off mode) cannot?
With shaded pole motors the startup current shouldn’t be an issue as it is relatively low. I am guessing it may related to a fan being an inductive load? I don’t know the hardware constraints but my guess would be TRIAC either in-line or parallel to the relay.
I believe it is a “true” On/Off (i.e., using a relay) and as a plus, you get a humidity sensor - which may be useful for a bathroom exhaust fan to control it based on shower humidity.
This is just my understanding of how things work . . .
TLDR . . . bulbs and motors are apples and oranges
Motors and light bulbs are electrically different, so the approach to speed control/dimming takes different approaches. The fan switch uses capacitor control to provide 3 speeds to the fan motor. That’s a pretty common approach for AC fans. However, capacitor control is not a suitable method for dimming bulbs. So the fan switch shouldn’t be used to dim bulbs because the mechanics are not designed for that.
On the other hand, the 2-1 dimmer uses a MOSFET or Triac to cut the waveform for dimming. That is not a suitable method for controlling an AC motor fan speed. So the dimmer shouldn’t be used to control a fan because the mechanics are not designed for that.
The 2-1 has an on/off mode, but that regardless of the waveform, it is still using the dimming circuitry. I don’t know if you remember Sam Kinison talking about world hunger, but if Sam were here to day, he’d be shouting ITS-A-DIMMER! (Sorry, Eric . . . )
Unfortunately, that wasn’t the original intent of how the 2-1 was hoped to be designed, but constraints kept the on/off portion from being relay-based. If Eric had his way, there would be a 3-in-1 but unforuntately there is only so much you can fit into a limited form factor.
