Modulation

I do not know any more details than the website for the Alpha boilers. They do advertise compatibly with OpenTherm so you should be fine to use that for modulation control. As I live in the Netherlands and all boilers have OpenTherm I was able to use the D01 configuration code with a "2-wire bus" wired connection to my boiler and it works much better than the "potential free contact" thermostat that I replaced. Good luck

So. i raised a support ticket with Tado asking :-1:

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" I have an extension kit that I was looking to connect to my boiler. I currently have a Nest 3rd Gen controlling my Alpha Etec plus 33 boiler thru OpenTherm configution and the system works very well, including modulation. I recently came across this post on the Tado community form which states that Tado could controller on Alpha boilers cannot do modulation
https://community.tado.com/en-gb/discussion/comment/20265#Comment_20265 "Geraint_Griffiths1
January 8
They came back to me yesterday to say Alpha doesn’t support modulation with Tado which is really annoying given the reason I chose Tado over Hive was the modulation facility."

Can you please confirm if this indeed the case?. Regards.
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After 3 days, and a bit of back and froth, here is the following:

Hello,
Thank you for contacting us.
If your Nest thermostat is the Heat link 3rd generation, tado can certainly replace that to control the Opentherm interface.
Please do let us know if you have any further question. We are happy to help.
Kind regards,

And finally...

Me: So, the community Forum posting is incorrect??

And response:

Hi Rizwan,
The post is not incorrect.
The fact is that the Alpha Etec plus 33 boiler does support two digital interfaces: 1) Opentherm 2) Alpha-BUS. tado° is compatible with Opentherm but not with Alpha-Bus. Since you are currently using the opentherm with Nest, you can use the same wires to connect tado to opentherm and replace your current room thermostat.
What I can assume is that the person only asked if the Alpha Etec plus 33 was compatible and probably has no current thermostat. Since we replace the thermostat in place (in order to avoid the customer opening the boiler), we normally ask if there is a thermostat.
Kind regards,

Santana

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So, if your boiler has OpenTherm control as an option, Tado should be able to control it fully including modulation. Looks like Alpha has two modes of control...Opentherm, is an open l, manufacturer agnostic standard and Tado should be able to work with it.

No, you need to.check if your boiler supports OpenTherm, and if it does, then Tado would do modulating control on it.