Whole house Fan control using Shelly 2.5 and Tasmota


I’m going to be installing a 2 speed whole house fan this weekend and wanted to get a little sanity check here. My plan is to use the High/Off/Low hardware switch that came with my fan to and hook it up to the Shelly 2.5 and set the interlock command in tasmota so that only 1 relay can be on at a time. And set SwitchMode1 1 and Switchmode2 1 in the console so that relays will follow the hardware switch state. The fan also came with a hardware timer that will go unused since I will want to setup a dashboard with multiple timer automations that will control how long the fan runs or base it on temperature. I’ll make sure to install a 2 gang box to install this later if I ever sell the house. I’ll have to figure the automations out later. The fan uses 662 Watts High / 480 Watts Low so the shelly should be able to handle the load(Specs state 10amps per channel). I want this to be something that my wife or a guest can go up to the switch on the wall and turn the fan on and have it work. Initially I’m going to set a 8hr max run timer and then add complications later. Even if they have to turn the switch to OFF position and then ON to get it to kick on if HA shut it down because of an automation and the switch is still in 1 of the ON positions. Is there anything I’m not thinking about? Any thoughts on best way to setup the a selections of timers on the dashboard? Like WH Fan High 2 hours, WH Fan High 4 hours, etc?

An automation idea: back when I had a “whole house fan” (it was a massive air king window unit), I created an interior heat index calculation based on a temp/humidity sensor and compared that to the exterior heat index from my weather integration. In the morning I would let the fan run until the exterior heat index started to go above the interior one.

I don’t have enough electrical knowledge to know how reasonable this is but it might be a bit nicer if you use a “momentary” switch like the ones used on in-wall smart dimmers. That way the state of the physical switch doesn’t conflict with the fan’s state, because the switch really doesn’t have one. You might have to sacrifice being able to adjust the speed from the wall switch but perhaps that’s not a big deal to your users.

@rob_c Hey Rob did you ever get your whole house fan set up with the shelly 2.5 I have a 2 speed blower motor for my heat, it only pulls 2 amps max. I got a shelly 2.5 to do the same.