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Sniffing the Buderus Logamatic 4000 bus

Avid readers of this blog might know that I already had a couple of projects around the heating in our house. The latest addition to these projects is a mechanism to listen in on the Buderus's bus to gather and log information such as outside temperature, target temperatures in the heating circuits, turn-on and turn-off temperatures of the burner, etc.

My intention with this information is to improve heating efficiency (as measured in gas used) and also to get a more in-depth understanding of the engineering aspects of this system (mechanical & electronic engineering and computer science).

Previously I've installed DS18B20 sensors all around, monitoring the system from the "outside", by sniffing the bus, I get a peek into the inside of the system.

When I started, I've found the site https://www.holzleitner.com/el/buderus-monitor/index-en.html which contained a reverse-engineered description of how the bus system of Buderus works.

Then I've stumbled into the  BBQKees webshop which sells complete boards to connect a Raspberry Pi to the boiler, from which I quickly purchased one.

Unfortunately the BBQKees board turned out to be incompatible with my boiler, but I've learnt a lot from trying to make it work:

  • had to le-learn electronics basics, voltage dividers, capacitors, etc
  • the use of an oscilloscope, even outside of my lab (e.g. connected to the boiler and various points on the board)
  • the electrical encoding of an RS232 signal

I couldn't make the BBQKees board work, which is a but of a let-down but I truly enjoyed the process. The details have been documented on this twitter thread.

With that failure, I decided to solder my own board, as described on the Holzleitner site. And with that I was successful.

My RPi is now receiving the 1200 8N1 signal that the boiler is sending out to the room unit, which I can now use to chart changes in boiler behavior in Homeassistant.

 

The chart shows a combination of data acquired via DS18B20 sensors and the data acquired via the bus sniffer:

  • the red chart shows the temperature of the hot water produced by the boiler (DS18B20),
  • the green one is the internal temperature of the boiler (reported by the boiler)
  • the two straight lines show the turn-on and turn-off temperature of the burners (also from the bus)
  • And the history chart on the top shows wether the burner is active or not.

This is just the beginning. I intend to attach a sensor to our gas meter, so I can relate the burning time with the amount of gas used. But I also have plans to change how the system controls pumps, as I am pretty convinced that the way it works right is not ideal. I am going to monitor this data, in order to get a baseline and to confirm my hypothesis.

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Jieffe said…
Great job ! I've grabbed the popcorn and am waiting for the next episode :)

I've got a Buderus boiler too and I'd like to retrieve data from it.
6:34 PM
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