After a few months off the case, I am back at looking at boiler replacement options with an opentherm connection. To date, I have considered ATAG but there are no installers in my immediate area and, latterly, Intergas. Valliant said that it wasn't a goer and I still await a response from Viessmann. Technical support teams tell me that their installers have been given some training on the opentherm capability but as there are so many opentherm devices on the market they have to led by the device manufacturer.

One forum that I read recently suggests that Intergas boilers do not cope with Evohome multi-zoning. The advice is that it may be just as good to install a boiler with weather compensation and no opentherm. I know that Evohome does not use external weather compensation but I struggle to see how, for example, a variable boiler temperature (weather adjusted) would work with, say, optimum start on a HR92? Wouldn't the boiler be continually adjusting and the HR92 continuously learning?

Another forum suggested that as most of the savings benefit has already been accrued by installing Evohome, the cost/benefit of opentherm doesn't stack up.

I am also struggling to get my mind round how a system boiler works with opentherm? I have seen a reference in the past that opentherm only works with combo boilers.

What I am looking for is a replacement system boiler for an Ideal FF280 in an 'S'plan configuration. The two BDRs control the 2 motorised valves.

Am I wasting my time with this? I am really not keen to have my Evohome set up 'destroyed' whilst a well-meaning heating engineer learns on the job.