oleg_tarasov

Maintainability is a concern that I haven’t figured out yet :) Right now my plan is to replace my DIY thermostat with off the shelf device suitable for my boiler when we sell the house. All the advanced features will be lost, but this still is the average expected level of automation in the area :)

After I finished debugging the prototype, it required literally zero maintenance throughout the winter. Actually we were not living at the house at all, contractors doing remodelling work were living there instead. I installed a LCD screen with basic temperature controls and they had no problem with it whatsoever.

Doing this project from start to finish took me 2 or 3 months on and off, mostly during the weekends.

Doing it right yourself is the exact solution I arrived at myself :) I was shocked to discover how low the average technical level of local contractors is. I was super lucky to find a highly professional guy to overhaul the pipework, but anything more complicated I had to study on my own. Luckily, there is a ton of youtube videos, so the only thing you actually need is time.

Yes, safety and robustness were my primary concerns while designing this project. This house is more like a vacation home, and we don’t live there permanently. So my main goal is being able to control remotely as much of my heating system as possible, making sure not to burn the house down at the same time :) Here is what I took into consideration:

1. My device interfaces with the boiler through optocouplers, so I don’t touch boiler circuits with my crappy engineering skills.

2. The boiler itself, as well as OpenTherm protocol, seem to be able to recover automatically from many failure modes. It doesn’t matter much if some frames are dropped or mangled, since full set of control signals is repeated every couple of seconds.

3. I rewrote critical parts of OpenTherm component for ESPHome to make code more resilient to failure. The whole firmware is designed in a way that incorrect values or broken frames don’t bring anything down catastrophically. I also made sure that boiler has its own maximum temperatures set to sensible values, so that incorrect signals from the thermostat will be discarded.

4. The device is designed to be completely self-contained and doesn’t rely on Home Assistant or Wi-Fi being up.

There are a couple of things that I plan on adding to this setup, like a Shelly relay on boiler power input to be able to do a hard restart remotely.

Ideally, I would also prefer not to McGyver a custom device, but unfortunately, there are no such dumb smart thermostats for my boiler that would allow remote control.