I’m looking to control my bathroom fan using the Smart On/Off Switch. Since the bathroom fan is powered by an ERV, I believe the setup needs to be a bit more complicated, and I’m thinking about using the Smart On/Off to physically trigger a dry contact Shelly 1 relay.
The ERV, which supplies 12V DC, is normally controlled by a Venmar wall switch that can control on/off and intensity and has a small LED to indicate of it’s on. In my case, I’m fine with just having on/off functionality, and it seems lots of people have swapped out the Fan wall switch for a Shelly1 so that they can automate the on/off functionality with HA. The Shelly can also be physically triggered by a “dumb” momentary wall switch using the I/O ports (I’ve seen people do this for a garage door opener). However, that wouldn’t provide visual indication of the fan being on/off.
So my question here is whether or not I can use the White Smart ON/Off switch (which I already have) to physically trigger the Shelly 1 via the I/O ports (or via another wiring setup), and also not overload it with 120V. While I know I could do this via automations in HA, I’m wondering if I can physically wire the Switch to trigger the Shelly on/off.
My understanding is that since the ERV supplies 12V, the Shelly can be powered by this. I’ve read that the Smart On/Off can control low voltage loads - would this apply? I think this would be a similar setup to using an smart switch to control a Garage Door relay. I’m also not clear on how the Smart On/Off needs to be setup to handle low voltage.