To remove the cloud dependency for my house heating, I decided to create this in Home Assistant. The requirements I set are:

• No cloud dependency
• Multi-room support
• Fully costimzable to my needs
• Auto on/off when somebody/nobody is home

Nice to have:

• Open Window detection

Hardware

Used boiler:

• Atag E325ec - 2015. This boiler supports the OpenThem Protocol

Thermostat

• DIYLess OpenTherm thermostat with custom ESPHome config

Because I want full control, I immediately pushed ESPHome onto the thermostat. But the DIYLess Thermostat has software on it that should work..

I mostly got my config from XXX and XXX

As I already have an OpenTherm Gateway, I already knew what sensors my boiler supports. I basically trimmed down the sensor config towards the sensor my boiler supports.

The hardest part of getting the thermostat dailed in is setting the PID-controller. ESPHome has an autotune function for this. But this only helped me so much. I ran the autotune once to get some initial values. It wasn't long before I found that with the parameters of the autotune, my boiler never got to the actual temperature. Digging around to find the actual meaning of those parameters, I was about to give up, but then I just asked ChatGPT for some help and it got me in the right direction. Awesome AI for once!

Thermostatic Radiator Valve (TRV)

• Sonoff TRVZB
• Shelly TRV Blu

Yes, you got that right. I use 2 kinds of TRV's. For two radiators, as I have limited space for the TRV's. The Sonoff TRV's just didn't fit, so I had to fall back to the Shelly's. The Shelly TRV's are very much like the Tado's. Both in dimension and in appearance. Here are the pros and cons.

Sonoff TRZB

Pros:

• Cheaper
• Completely local
• Supported by Zigbee2MQTT

Cons:

• A little bigger than Tado (and Shelly)
• Control is somewhat complicated. You can control the valve opening, but not very straightforward. At least not when using Zigbee2MQTT

Shelly TRV Blue

Pros:

• Small, about the same size as Tado TRV's
• Possible custom firmware?

Cons:

• Expensive
• Still dependent on a third party
• you need a stick to control them
• You need another integration in HA (Shelly)
• Very limited control.