If your boiler supports OpenTherm then get this thermostat controller https://github.com/Alexwijn/SAT

Weather comp + low load comp + PID which means your room temperature works at the precision range supported by your temperature sensor. In my case, within 0.02 Celsius. Saves energy and makes your house more comfortable. Operated via home assistant.

See real time data in Grafana

https://gasboiler.grafana.net/public-dashboards/8d44381aafa9...

Or Emoncms

https://emoncms.org/app/view?name=MyBoilerIdealLogicH24Opent...

I'm very interested in this— I have a fairly new Vitodens 100 boiler + Ecobee and also a heat pump system with its own thermostat, and I'm frustrated by several elements of this setup:

- The Vitodens has like ten stages, but the Ecobee has no way to command them, it's just a binary call to the Taco pump for heat / no heat, with the boiler deciding on its own how hard to push (I guess based on the outside air sensor and maybe time of day?)

- The Vitodens is monitoring the return boiler water temperature, but the Ecobee doesn't know anything about that.

- None of this is interlinked with the heat pump, so the systems can run on top of each other and end up with the wrong parts of the house overheated or left cold. The heat pump's controller is proprietary but it works with the NetHome Plus app so there is a bridge to get the units on homeassistant.

I don't have the spoons right now to try to beat this all into shape, but eventually I'd like to get HA temp monitors in multiple places in the house so that a single central system can make smarter decisions about which system to run and when. For example, in the evening I mostly care about the bedrooms, and the bedrooms are covered by zone 2 of the heat pump, so it would make sense to prioritize the heat pump then and only run the boiler if the heat pump isn't able to keep up; whereas in the daytime if heat is needed, it's probably throughout the house so the boiler should run.

Aawww, this looks so nice!

I really would want a more clever solution for our heating: district heating that goes int our "legacy" high-temperature old radiators, and also a secondary system with under floor heating but with a limited temperature. The problem is the "secondary" system is much bigger and heats most of the house, but is more or less unable to change its temperature since its always "capped" at the max since its driven from a high-temperature system, the shunt can not lower the temperature, also its a dumb one. So we have bang-bang thermostats everywhere for the floors which works, but is not at all optimal.

Stuff this project tackles is on my "I'll get to it after I retire" list - super awesome. Looks like this works for forced air HVAC as well?

There's also ems-esp which I use on an older Worcester Bosch boiler to set flow temperatures based on the outside temperature (managed by home assistant).

Thanks!

Which OpenTherm device would you recommend?

We replaced a boiler in our last house a few years back. We got a Vaillant, at least in part because I found that there was a Vaillant add-on board available which could do OpenTherm, and the nest controller could do that in theory too.

When it came to the install I was told in no uncertain terms that even though they produced the board and it was compatible with my boiler, any attempt at installation by myself or their approved installation engineer would immediately void the warranty.

So that was the end of my OpenTherm journey. Thanks Vaillant!

Any good multi zone ones for home assistant?