Evohome + Opentherm + Viessmann Vitodens 100

[Stulin]

Congratulations, that certainly looks nice

Thanks Bart.

If you are still using a Home Assistant system I am happy to share the code and image files.

Cheers Stu.

[Bart]

My gateway had a fatal kitchen hardware related accident, I've just ordered a new one yesterday (goodbye summer) so I expect to continue from where I left pretty soon.

[Stulin]

My gateway had a fatal kitchen hardware related accident, I've just ordered a new one yesterday (goodbye summer) so I expect to continue from where I left pretty soon.

I hope the gateway didn’t become part of a soup. Seasoned with Opentherm.

Plenty of 3D printable OTGW cases out there. Mine only cost £12 to print. Worth it even though my OTGW is out of reach from accident prone fingers.

[Bart]

No, it got stabbed by a knife.
I've ordered a case as well this time. Not sure though about the next move of the enemy, I hope that my defensive works will be capable of withstanding any future attacks.

[Richard]

Ok, after many months I've finally got my evohome | vitodens | opentherm | home assistant system setup and am pretty happy with the outcome.

https://flic.kr/p/2hdrdfA

This is really awesome!

[Stulin]

Ok, after many months I've finally got my evohome | vitodens | opentherm | home assistant system setup and am pretty happy with the outcome.

https://flic.kr/p/2hdrdfA

This is really awesome!

Thanks, I really appreciate the kind words.

[Fr3eWar]

Ok, after many months I've finally got my evohome | vitodens | opentherm | home assistant system setup and am pretty happy with the outcome.

https://flic.kr/p/2hdrdfA

This is really awesome!

Thanks, I really appreciate the kind words.

Really nice gif,

Can you describe a step-to-step guide, how you managed to have a working opentherm solution?
I build a new house, and brought a Vitodens 100-W Touch 26kW B1HC026 boiler (just because of opentherm i choose viessmann, here in Hungary you can not by another opentherm boiler).
And im afraid at the moment from this setup.

I got already my R88 Opentherm relay, got Evohome WiFi controller, got HCE80 floorheating controller +HCS expansion, have 12 floorheating circles / 12 MT4-230-NC motor, (and would like to control it in 8 zones). Got HRA antenne, got ATF600 wall mount.

What else do i need?

[Bart]

"working" is relative, I am not sure what you are referring to.
You can just connect the opentherm relay to the VIesmann opentherm connection (see manual), setup your system as per evohome manuals, and it will work.
The major issue with the Viesmann is that you can't set the maximum heating water temperature when it is connected to opentherm. It will default to 80C max - meaning that the evohome controller will ask for water temperatures anywhere in between a minimum (don't know what that minimum is) and 80C.

[Fr3eWar]

That would be a big problem with my only floorheating system. Water temp should be between 30-40 °C.
What will i loose, if i connect to boiler with BDR?
The domestic hot water is made in an 200l indirect puffer by the boiler with factory viessmann NTC temperature sensor

[Bart]

For underfloor heating you can add additional thermostat mixing valves and pumps that will limit the temperature to a sane value, but it will complicate the setup indeed. And also that would probably make sense if you would have a mixed system with classic radiators and under floor heating.
Moving away from opentherm will give you the ability to limit the water temperature using the setting on the boiler, evohome will then modulate TPI, meaning the boiler will start and stop periodically (by default 6 cycles per hour) so tat it can maintain a steady room temperature, but the water flow temperature will oscillate more in comparison to opentherm.