Opentherm UK

I have recently installed my Tado Starter Kit and TRVs and am delighted with my installation. I would now like to go further and have more control.
I read from other contributors that Opentherm has been removed from UK Wireless Receivers so a wired Thermostat required. To be clear if I can source a EU Wireless Receiver and replace my UK Wireless Receiver would this enable me to have Opentherm.
One other query regarding my system is there a problem with having System Boiler (i.e a separate hot water tank) and Opentherm.
Has anyone had any experience with the Sapphire Boiler which is Opentherm compatible


  • You’re not going to be able to use Opentherm with a system boiler unless you replumb it for priority domestic hot water. If you’re willing to do that you can use either an eu wireless receiver or a wired thermostat.
  • @johnnyp78, is your replumbing comment just about the need for a legionella cycle, or is it more fundamental than that? I can see how there could be an issue if the hot water is calling for 60C and the WC is proposing 50C. I'm a novice at this so could easily go wrong and multiple attempts to get a local heating engineer involved have drawn a blank. Either way, can I use the immersion heater to handle the hot water (it's cost-competitive for me overnight)?

  • Yes, it’s to do with legionella and also that you can’t use a hot water relay with a digital connection. It’s either relay or digital with Tado.
  • Roughly half the actuators in the wired thermostat sit unused... such a waste of capital/potential. Boiler connected via bus, relay could be used to control a valve or indirectly switch on a coil for hot water, a pump, an IR panel, garage door, fan, dehumidifier, UV-steriliser, or just one of those 70s disco-balls...
    If using relay to control CH, the anolgue/ bus-driver side could maybe be used to interface with an always-on display, log data to some graphing tool (for example on a computer, or go for a hardcore paper-trail, polygraph style!), get fed information from auxilary sensors or send out telemetry over RTTY, depending on what the exact possibilities of this port are.