Old floor heating control made smart

Hi dear community!
Just wanted to share my latest project automating my home.

We had an about 20 years old floor heating control called “Velta Genius” with a central unit controlling the thermal circuits and remote units in each room where you could set the temperature which also had a temperature sensor.

The system got more and more unstable, getting replacement parts got harder and expensive.
So I had a closer look and the main unit and found basically two PCBs in it, one with all the logic circuits and processors and stuff and another controlling the main power to each thermal circuit.
So it was quite easy to design a replacement logic board based on an ESP8266.

Here the original unit with remotes:

And the original unit PCB:

And here with my replacement board:

I designed for an ESP8266 module but finally I used an ESP07S module with an external antenna, because the units are at rather problematic places in the house WLAN wise…


!!! That’s impressive. Did you basically reverse engineered the board?
This is waaaay beyond what I am capable of, and I personally could not call this “easy”. Is there any blog post / video somewhere that you documented your journey?

Yeah quite some reverse engineering but it was quite easy.
The split between high voltage and low voltage was obvious.
Regarding the function to just switch 230V on 12 channels looking at the markings of the components it was easy to know the function, just an opto triac and a triac as a switch controlled with a low voltage.
Getting the low voltage was also quite easy (I could have measured it), on the right side is a relay as far as I can see it was meant as an isolated output where you get if heating is on or off to another device, this was not used. The relay has a control voltage of 5V and was directly routed to the logic board to a transistor, so a simple transistor switch…
Rest was easy, 15 pin cable, 1-12 control the high power switches, 13 controls the relay, 14 is supply voltage and 15 is ground.

The nice thing was because of the separation I could use the high voltage board as is without have to deal with regulations or safety…

Sorry I have no blog, I made a presentation for our FabLab but in German and just some slides with pictures…

I am still planning putting this open on Github with a detailed description.

Thats nice!
How do you messure the temperatures in the rooms?
I’m also very curious about your heating controller :smiley:.

I’ll try to do this with a PID but with the slow floor heating it was not very good.
Now I’m using simple Single-point controller…

I placed Zigbee temp sensors in every room with a cental placed RPi with a DeConz module and image connected to my HA.
I just use the single point thermostat controller of esphome and HA.
As a floor heating is so slow I dont think anything else might have a lot of benefit…

BTW browsing through some offers of old modules to buy one as spare (one of mine seems to have a little problem with the power supply unit, I had to add an additional capacitor on the 5V to get it stable for the ESP) I found that the relay is meant to control a pump.
That’s why it always turned on if any thermal circuit got activated.
I don’t need that but you could easily built that function in a sketch for ESPHome…