Viesmann DHW Control - Set Temperature in ECO mode

I have Viessmann Vitodens 100-W B1kF connected via OpenTherm to a Wireless Receiver (EU) version. There seems to be a problem with DHW and I would like to share my experience after investigating and talking to Tado about it.

I hope this suggestion will help others so that maybe Tado implements it.


Viessmann has 2 DHW modes: Comfort and ECO.

  • In Comfort, you set a temperature and the Combi Boiler tries to have it more easily ready for you. This is the part you can control from Tado at the moment (set a schedule and all) with a value from 30 to 60 degrees Celsius. Mind you this option consumes more energy (especially gas); In my experience 0.2-0.5m3 per day more than ECO.
  • In ECO you should be able to set a DHW temperature to your liking and the boiler will only heat the water on demand.

The problem with Tado and Viessmann on OpenTherm is that you cannot set ECO DHW.

In theory from the app, setting DHW to OFF should enable ECO on the boiler, and you set the desired DHW temp from the boiler. There is a bug or a miscommunication between them.

So what happens? Setting OFF in Tado, makes the boiler go to forced comfort and the DHW temp to 55 degrees Celsius. Which you can imagine is a huge wasted of energy.

Now, I have 10 emails exchanged with Tado about this, and the summary is that they know this is an issue, and they are in contact with Visemann about it, BUT, they can't give an ETA or if this issue will ever be addressed.

In my opinion, this is a big issue and would love to see it fixed, as it's so far the only bad experience in my Tado setup.

Has anyone had this issue with OpenTherm and the Wireless receiver, maybe Viessmann or another boiler?

4 votes

Active · Last Updated


  • @Ruffinsky I presume that there hasn't been any further response from Tado or Viessmann on this?

    I am thinking of replacing my current aging boiler with a Viessmann Vitodens 050-W or Viessmann Vitodens 100-W, but this seems like a deal breaker for me, as judging by your estimated gas usage in comfort mode, this would possibly mean £100+ on extra gas cost over the period of a year?

    Is there a way to force ECO DHW from the boiler?

  • GrayDav4276
    GrayDav4276 ✭✭✭
    edited December 2022


    I'm not sure about the latest version of the Viessmann Vitodens 050-w is 7 years old ......but my version does not have the "ECO" mode for the hot water.

    I would like to think that Viessmann would be able to deselect the "ECO" mode......but maybe a Viessmann Engineer would need to visit your property to do this.

    I am considering a new Viessmann boiler.......but obviously I wouldn't want the"ECO" mode either.

  • Hello
    I have the same boiler and problem as ruffinsky….
    Im also waiting for tado to respond my email
  • I think another forum member posted and Viessmann can indeed force it to ECO. I personally choose not to do this and hope Tado will fund a solution with Viessmann at some point.

    For now, I keep DHW at 30 degrees when not using it and only turn it to the required value when we need it.

    Tado says if more people need this feature to work correctly they will fix it.

  • I have the same problem with my new vitodens 050w B0KA, i want to keep the comfort mode in day hours and turn it off when i'm sleeping or in holidays...
    I have write to tado-support and i'm waiting for answer...
  • I had a viessmann engineer out last week to change it so preheat is off with OT. Was done under warranty at zero cost. I mailed viessman after sale to arrange it.

  • @FranSuarez
    I really don't think that tado° would be capable of doing anything about this for you.
    You will be more likely to get a realistic response from Viessmann.
  • FranSuarez
    FranSuarez ✭✭
    edited December 2022
    @GrayDav4276 "capable" as they are not able to do that because it's impossible, or because they don't mind?
    Really I don't want to set Eco mode, i'm ok with the preheat option. But it's a bug that they would have to solve that when I turn off the HW in tado, the boiler sets the t°C at 55°... It has no sense.
    How it works with other OT Boilers?? What i am suposse to do when i go out of home for a week, turn off manually the boiler itself so it doesn't preheats watter everyday?
  • @FranSuarez unfortunately it seems to be due to the way viessmann boilers operate. Tado is just using the Opentherm protocol. the preheat issue doesn’t happen on my ideal boiler using Opentherm, for example.
  • According to viessman using OT mode on the boiler: "Comfort / Eco function is applicable via Opentherm thermostat", and "Activation and deactivation of ACS standby mode can only be done through via OpenTherm thermostat". So it shouldn't be difficult to add that option in tado...
  • johnnyp78
    johnnyp78 ✭✭✭
    I think that’s referring to viessmann’s own Opentherm thermostats. I suppose it wouldn’t be out of the question for Tado to add an option in the pro app if you tell it you have a viessmann boiler though.
  • Mr_Fruitbat1
    edited January 9


    I’m with you on this, it’s almost definitely caused by the command that Tado sends to the boiler.

    Whatever command Tado is sending when OFF is selected it’s causing the boiler to reset the DHW temperature to its default, rather than selecting Heating Only. You can select Heat Only in the ViCare app and it turns off DWH but it’s overridden by Tado almost immediately. If you can do it in one app you should be able to do it another.

    Another thing, just in case anyone’s missed it. Don’t forget to set the Away setting to On and the temp to 30. If you don’t it’ll turn the water off, therefore ensuring it’s a toasty 55 when you’re away.

  • I'm also interested in this topic. I observed what @Mr_Fruitbat1 stated previously and to be honest this seems to be a bug in the Tado software.

  • Has there been any further updates on this issue? I have the same problem
  • See other posts on the tado forum. I emailed viessman a couple of days ago regarding my new installation with wired tado and they initially told me that because I was using opentherm the boiler would function as a slave unit and eco and temperature controls would be disabled. However I sent them a link to the relevant forum posts and my serial number and they changed my settings remotely. I have full control over the hot water on the boiler and the vicare app and eco mode is enabled and working.
  • Just to reiterate what was said above, I emailed Veissmann yesterday with a link to this topic and a screenshot of my serial number from the ViCare app. They sent me an email this morning confirming they had remotely updated my boiler and enabled the DHW control again. I now have put the boiler in ECO mode and it works as expected.