I have a textbook Evohome Y plan system, set out exactly as in the Evohome wiring guide. Two controllers bound to a single BDR91 for heating, and one of the controllers also bound to a BDR91 for hot water.
I am now looking to convert this to O/T boiler control using the R8810A, as opposed to BDR91, with a new boiler installation.
Obviously the R8810A will be wired directly to the boiler, and the two controllers rebound to it instead of the existing BDR91, but what wiring changes to the basic Y-Plan are required?
Any guidance would be highly appreciated - it's the working of the three-port valve this is perplexing me!