viessmann vitodens 050-w and Opentherm

edited September 2022 in General Questions & Topics


I've just had this boiler installed and want it to use Opentherm which the boiler is compatible for.

The old boiler didn't have modulation.

I've had the tado system for around 4 years now so have the below setup:

extension kit which is wired directly into boiler.

internet bridge.

6 wireless radiator thermostats.

5 wireless add-on room thermostats.

I've attached a screenshot of how my current extension kit has been wired into the boiler.

How can I get this wired up so my boiler modulates the heating using OpenTherm?

Your help would be much appreciated as the main reason for buying this boiler was because it can modulate the heat and is Opentherm compatible.




  • The extension kit wiring is the easy bit. You need to move the grey and black wires from 1 & 4 to terminals + & - on the right hand side. Before you do this you must alter the wiring inside the boiler. It's really important that you disconnect the 230V wires at both ends before re-connecting wires to the low voltage terminals.

    Unfortunately to access the wiring inside the boiler you need to remove the boiler casing and break the combustion seal. If you are located in the UK you cannot do this yourself - it must be a Gas Safe heating engineer. Not sure what the regulations are in other countries.

    Once the wires in the extension kit and boiler are moved to the OT terminals you need to contact Tado support and ask them to update your system for OT control.

  • thanks alot

    found this video online which shows the boiler side of things but just couldn't find anything relating to the tado configuration.

    How To Wire Viessmann 050-w Opentherm or 240v switching - YouTube

    i'm in the uk so will see if i can get the same company that installed it to change the wiring over (without charging extra), fingers crossed.

    the image which shows the other side of the case for the extension kit, do i leave the orange bit in the "1" position which is Relay wiring 1 - Potential free or change to relay wiring 2 - switched live?


  • The orange jumper has no effect when using Opentherm.

  • GrayDav4276
    GrayDav4276 ✭✭✭
    edited September 2022
    As @GrilledCheese2 said....
    The jumper is not required for Opentherm with this boiler.
  • so just had the boiler wired up for OpenTherm, changed the wiring on the (old style) extension kit and got tado to change on their end, all seems to be working fine.

    my boiler has a pre heat option (eco mode) to keep the water warm.

    when eco mode is off, the boiler fires up every hour to keep the water temperature warm.

    when eco mode is on, it doesn't fire up the boiler which is what i prefer (saves gas, etc).

    now with everything changed over to OpenTherm, there's no option to select eco mode on the boiler and it is firing up every hour to keep the water temps around 60 celcius :-(

    any ideas why this would be please?


  • I believe customer support will have to make this change for you - not possible through the app.

  • Just to add, is there a reason you need to keep your water temp at 60c? You have a combi with no tank so there’s little danger of legionella, might as well set it to a usable temp like 45c.
  • @GrilledCheese2 tado said they have the Opentherm setup on their end

    @johnnyp78 it's doing this automatically at the moment. seems like, everytime it drops to around 40c the boiler kicks in and heats it up to 60c.

    does this during night aswell which is really annoying.

    i think its probably something on the boiler side of things, not sure.

  • In that case, ask customer support if they can turn off preheat, seems bizarre that the boiler’s heating above the level you want it.
  • Bantam81
    edited September 2022
    @Ervcrt100 did you get this problem sorted I'm having the same problem both with Tado thermostat and Nest. I assume it's an issue with the boiler. Had to remove opentherm link and have it as on/off system.
  • I don't think that the Viessmann Vitodens 050-w has a "Pre heat" feature for the hot water...........
  • so looks like this is how OpenTherm works.

    the eco mode is no longer there and that is how it is meant to be when in opentherm mode.

    the boiler coming on hourly etc is also normal when using opentherm :-(

    i've been told that on the long run, this will save me money so for now, i won't be switching back to the relay on/off mode.

  • GrayDav4276
    GrayDav4276 ✭✭✭
    edited September 2022
    Are you sure that this new boiler actually had the Preheat Viessmann Vitodens 050-W doesn't have this and has Opentherm via my tado° system.
    Also the boiler in the video does not look like my 050-W.......does your boiler look like the one in the video ??🤔
  • yeah, this is the latest version of the boiler, has a digital screen on the front.

    i've installed the hot water feature in the tado app and have had some luck. during the day, i've set the water to 50C and night time i've turned it down to 30C. now it doesn't fire up as often, seems to have helped alot by doing it this way.

    i've got a case open with viessman to see if the pre-heat option can be turned off via the boiler somehow.

  • Hi @Ervcrt100
    I have spent a few hours on YouTube today.......and I have worked out that my 050-W is the previous version, so yours is the latest one.
    The videos show that you can switch the ECO mode on or off.....however from other posts regarding tado°s Opentherm operation with combi boilers with ECO feature.....the general impression that I get is that tado° appears to override the boiler ECO settings......which isn't a good idea imho
    Keep us posted on the response that you get from Viessmann.
    I like the look of your 050-W......I'm tempted to upgrade.
  • to keep this thread updated for future searches etc.

    viessman engineer has been able to enable eco mode with opentherm running.

    eco mode is now enabled for the hot water and tado will deal with opentherm for the heating side of things.

    he had to access my boiler via his laptop and hardcoded the pre-heat function to not be available.

    i can adjust the HW temps via the front of the boiler (digital screen) aswell as enabling eco mode and this can be done via the ViCare app aswell which i would recommend installing if you haven't, good app.

  • Hi! I have bought this boiler and i have the same problem, the boiler runs every hour to keep warm watter available for ACS.
    And i have noticed that if i turn off the HW in tado app the boiler doesn't turns off the preheat , it sets at 55°! So the minimum t° i can set the HW is 30°, that it's completely unnecesary ant night... During the day i have set it at 45°, hot enought for showers...
  • @FranSuarez if your in the UK, reach out to viessmann after sales support via email, hopefully they can send out an engineer to override the pre-heat option.

  • Hi @Ervcrt100
    Is your boiler still operating as you wanted it to..... ie in ECO mode ?? 🤔
    Also are you pleased with your boiler?? 🤔
  • Hi @GrayDav4276

    yeah it's still in eco mode, so looks like no updates from tado can override the setting done by the viessmann engineer.

    it's alot better then my old one :-)

    its the first winter season with this new boiler and opentherm, i think its ok but would be interesting to see how WC would behave and how differently.

    i have the max flow temp set to 60C.

    in the colder days, does seem like boiler is running more or less all day but i suppose that is expected as running more efficiently, well i hope so.

  • Floob
    edited December 2022

    For what its worth, on my Vitodens 100-W, I have pre-heat on, and in the ViCare app, I see:

    and on a day when no-one was in and the heating set to off, my gas usage was this (measured by energy supplier smart meter). So on the face of it, it fires up for about 3 minutes every couple of hours or so.

    So whilst my Tado app shows this, it doesnt seem to equate to much in terms of actual usage, I guess because its a combi and doesnt need to maintain a whole tank worth of hot water?

    My config is set as:

  • FranSuarez
    FranSuarez ✭✭
    edited December 2022
    @Ervcrt100 i'm from spain, sorry for my english 😅

    Thanks for your info @Floob it seems really low waste of energy&money*, but its also unnecesary at night, holidays... And i dont want yo have to switch off the boiler everyday...
    * 0,12kWh/h *24h *365d *0,07€/kWh = 80€/year aprox..
    I cannot see in my tado app the "config screen" that you posted in the last image, how can i access to it?
  • Floob
    edited December 2022

    Hi @FranSuarez

    Bear in mind it will be half that, so approx 37 Euro per year, as its 0.12kWh used every 2 hours. But yes, not using this at all would be cheaper. I think I've got used to having instant hot water now though.

    To see the config screen, use the free "Tado Pro" app, and scan the QR code for the bridge unit when prompted under the "System Check" screen.

    Viessmann told me:

    "Once Opentherm is connected, the Boiler panel no longer has any functional control so it would not be possible to change yourself manually. We do not have any costs on Gas usage when operating under Pre-Heat I'm afraid, the assumption has always been that it can only be a small amount of gas as it is not heating up the property, just the internal pipework and plate heat exchanger in the boiler itself, which, over a 24 hour period may not amount to more than 'Minutes' in real terms rather than hours. "

    When I asked about why the pump comes on sometimes, they also said

    "The pump will run on after a water demand for 3 minutes and after a heating demand for a minute . Occasionally if there has been no operation the boiler may do a system check also "

    For the system checks above, they said:

    "This would only be a couple of times a day generally if there is no activity on the boiler for normal operation "

  • FranSuarez
    FranSuarez ✭✭
    edited December 2022
    Thaks @Floob for all that info!
    I have tado pro app since I used it to check the compatibility and connect&configure the boiler and tado. Now I see that menu, and also that i can set a Max flow T° in that menu (not necesary to me because I have already change it in the boiler parameters because 82° seem to be too high).
    I also have seen that in the tado pro app Configuration menu there is an option to uncheck the "HW control" so maybe its possible to configure opentherm without HW control, and keep the option to change Eco/confort modes and the t°c from the boiler... ¿?
  • I'm in the same situation. I just switch from On/Off relay mode to Opentherm with a Vitodens 100-W BK1F.

    Opentherm works pretty well for the heating circuit.

    But not for Hot Water. If I turn off HW on my tado application, my vitodens still produces HW.

    And I also loose the Eco mode.

    So I tried to disable the HW control by reconfiguring my tado. But the eco mode stay unavailable.

    It seems once the vitodens is configured to use opentherm, the eco mode disappears.

  • @Damgot the only way to get eco mode back after enabling opentherm, is to get a viessmann engineer to come and visit you. they need to connect their laptop to your boiler's wifi to override the setting.

    mines been working fine with opentherm and eco mode enabled (pre-heat off).

  • Did the viessmann engineer charge for the disable pre heat function modification
  • @clive35 no they didn't. boiler had only just been installed, so maybe they done it for free as in warranty, not sure tbh.

  • @FranSuarez

    I’ve notices if you set it to 30º it doesn’t actually preheat. Last night the heating went off at the usual time, I checked the boiler starts with the vicare app, when I checked this morning the boiler hadn’t started once over night and the water temperature had dropped to 22.8º

  • I monitored my viessmann and it did fire up for preheat with the dhw temp set at 30 degrees.