The Panasonic exhaust fans can have quite complicated wiring. I just installed one that has seven wires in it, all for different purposes. 3 are related to the integrated light, but even discounting that, it’s still a 4-wire fan. The first thing I’d recommend doing for troubleshooting is making absolutely certain which wires are which, and how you’re connecting the inovelli switch. This will require testing with a multimeter.
Panasonic has a 9-year-old youtube video explaining the wiring. The way they handle the light/night light has changed since the video, but the fan parts are still accurate.
On mine, (excluding the light wires) the wires in the fan (in the junction box attached to the top of the fan) are:
- Neutral (white). This is the only one that’s simple.
- Constant hot for the fan (Black). This powers the electronics which handle things like delayed start, automatic start based on plug-in humidity/motion sensors, and multi-speed for constant low-speed ventilation. It also powers the fan.
- Dry contact 1 (red)
- Dry contact 2 (also red, indistinguishable from dry contact 1).
The two dry contacts are not suitable for any AC voltage on them. They are only supposed to be either connected to each other or disconnected, using a dumb switch or a dry contact relay (which inovelli doesn’t make). I remember metering them an I think what I found was that one of them was connected to the AC neutral and the other had a small DC voltage on it, applied by the electronics of the fan, which got pulled down to neutral when the dry contacts were closed.
If you have a setup that runs constant power to the fan, then dry contacts to a dumb switch, you will not be able to replace that dumb switch with an inovelli switch. In my house, I’m actually putting relays on all the “constant” hots for my bath fans, so I can monitor power consumption and cut off the fan if I really want it off, even when the built-in humidity sensor would otherwise have it on.