Evohome and Opentherm

[edhodges1984]

Hi all,
I have searched through the threads and there is loads on Opentherm but I can’t seem to find my answer.
I have a system boiler with evohome + hot water kit. I wanted to look at getting Opentherm but confused as to what the Opentherm relay replaces.
So I buy the Opentherm and hook up to boiler, does this replace the CH BDR or the DWH BDR or both?
Just need some clarification on this matter and there are many experts here who will invariably know the answer.
Thanks

[G4RHL]

I can’t answer all of your query in the sense that my boiler is a condensing boiler providing heating and hot water. No system tank. I installed the Opentherm Bridge in February last year after the boiler was replaced. The Opentherm Bridge takes the place of the BDR relay used for central heating. I imagine it would not be much use for heating domestic hot water and for that, if I had that system, I would retain the BDR. With CH the Bridge works very well. It plus the new boiler keep the CH nicely balanced.

[edhodges1984]

Thanks I did think that was the case. I didn’t clarify, I do have a condensing boiler but it’s a system not a combi, I have a tank for HW.

[bruce_miranda]

The OT replaces the Boiler Relay. I.e. the box responsible for firing your boiler up. It responds to either CH or DHW demand. But you will need a separate DHW BDR91 to open the valve to the HW tank on DHW demand.

[Stevedh]

Note though, as you probably already know, it will also be connected to different contacts inside the boiler so its not just a matter of swapping it with the relay box.