Open Term vs Relay Connection to Boiler


I am considering purchasing a Tado "Starter Kit – Wireless Smart Thermostat V3+" and lots of "Smart Radiator Thermostat V3+s".

My boiler is a "Remeha Avanta 30s", S-Plan with an external Megaflow hot water tank.

Before I purchase I have 3 questions I hope someone can answer:

1) Does the Wireless receiver in the starter kit allow for Open Them connectivity to the boiler?

2) If not would I be better getting an Extension kit?

3) What are the advantages to using a Open Therm connection to the boiler versus relay control? I have heard that OT might offer boiler output modulation and so be more efficient?

In other-words is the OT interface more than just a low-voltage on-off or does it depend on the boiler and or the version of OT it support?



  • sdmaino
    sdmaino ✭✭✭
    edited February 16

    I can answer only to question #3

    Yes, OT can give you power modulation , with great advantages in terms of boiler efficiency, while relay control can only turn your boiler on/off.

    In orde to use OT control your boiler must have this protocol and being pre-set to manage different modulation steps.

    Higher number of modulation steps -> better modulation -> higher power save as the boiler will be nearer to the required heat.

  • Tado can’t do OpenTherm and S Plan.

  • Hey Montage - please could you expand on that? Why can't you have S-Plan plumbing but use an OT boiler control?

  • It’s a technical limitation of Tado (and Nest). They will only do ebus OR relay switching.

    If you have a means of solely receiving ebus and that device can itself sort out your valves then you are fine.

  • >They will only do ebus OR relay switching.

    Oh that's a shame, thanks for the info!

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