System boiler with Opentherm PDHW - X PLAN
I want to know if people are using Tado X with opentherm on a system boiler and tank using opentherm? from my understanding this needs to be configured as PDHW. If you have this type of setup work I would love to see what you have and how well this is working.
Answers
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Tado doesnt offer a HW cylinder temperature sensor or thermostat for HW cylinders. To make this work you'll need to find out if your manufacturer does one or more of the following:
- It recommends a sensor for the HW tank/cylinder, which can talk to it in Opentherm.
- It is compatible with a wiring centre that handles the required zone valves and will talk Opentherm to the boiler.
Some manufacturers offer a diverter valve which is triggered by Opentherm, for their boilers. Once the hardware is available, a discussion about Tado potentially working with that boiler can begin.
What exact model of boiler is it?
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This will be a brand new install I was hoping to install the following
Viesmann 100-W system boiler and 300L tank
4 pipe PDHW
Use Tado X for controls
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Would strongly recommend you write to support@tado.com, give them your account details, attach these bits of information. The support team have the job of researching this. From everything you have provided you seem to have overcome all the obstacles to operating it in opentherm mode. However Tado support must give you formal confirmation. If they give you a merry dance, come back here and we can help push back.
None of us are Tado employees, we're just end users like you. I used to have a 100-W in my old place and Veissman gave my heating engineer the run around when I tried to get the boiler working with Tado- had to give up and use their controllers.
However many did get it done. Others had a hard time. So it seems the best, most reliable way is to get support to map it out for you in writing. Make sure they have your full correct model number of boiler, the exact part numbers you are aiming to use.
And come back here and let us know. If you need further help come back and we will try.
Am hoping this year to summarise end-user contributions in addressing implementations with the Vitodens cluster of boilers.
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Given the boiler has the diverter valve, you shouldn’t need to fit any zone valves (aka X Plan). I would avoid that term when discussing with Tado.
You just want to drive the Viessmann using OT to command the DHW as well as heating. The boiler will do the hot water as PDHW, by using the internal diverter valve.
I’m planning to change to a Viessmann 100W system boiler shortly. As I don’t want the extra piping, I plan to have an NO valve on the heating and an NC on the DHW circuit (usual X Plan). I understand you can stick a relay inside the boiler and let it think it’s doing 4 pipe. Not sure I’ll use OpenTherm, as I want to run weather compensation using the Viessmann set-up. We’ll see how it goes.
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@vmguru Did you manage to make any progress on this?
I'm in a similar situation to you: I've already fitted the Tado-X radiator valves and programmer (UK model) and the next step is replacing the old system boiler (on S-plan) to something with load compensation. I'm not scared of re-plumbing the system but I don't want to go down an evolutionary cul-de-sac with the choice of boiler 👍️
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