Hybrid system layout to ponder

[Beelbeebub]

If you're up for a bit of tinkering how about a raspberry pi, or better yet a raspberry pico interfacing via an open therm interface unit.

 

Gives you full control. Cheap and robust, especially if you use a pico.

 

I've used an arduino to control my thermal store and boiler for a decade or so.

 

Just uses relays to activate the boiler and some thermal dumps to prevent overheating (there's solar and wood boiler attached).

 

Absolutely rock solid. No need for Internet or any other external stuff.

 

Does interface with home WiFi so temperatures can be monitored and parameters changed without having to plug into unit in airing cupboard.

 

Has a little LCD display with push buttons and dial for viewing data and switching seasons (in summer the thermal dump to the UFH is disabled and it just dumps hot water down drain, in winter it dumps into the UFH first)