Hi:

My house has two boilers wired in parallel. One BDR91 turns them both on for heating, and another turns them both on for hot water and operates the appropriate valves.

I'm not sure if it really needs two boilers, they were there when we moved in.

We've always had some noise from the heat expansion of the pipes when the boiler comes on. This is less if the boilers are at a lower temperature, but then the hot water takes a long time to get to 60 degrees. The boilers are getting oldish (20 years) and according to british gas some parts not replaceable although not yet at the stage of causing a servicing problem.

Since installing evohome the heat expansion noises from the pipes are worse because of the TPI. The house is much more evenly heated though.
So - first thought is whether opentherm would help - but can it control two boilers at once? (Assuming I swapped for opentherm capable boilers). If it would help, I also wonder whether I could actually have one boiler and the system was originally over-specified.

The water heater is a megalow - we've never had the radiators flushed through or anything, so I do wonder if we did that whether it would heat more efficiently needing a lower temperature and reducing heat expansion noise from the pipes that way too.

Any ideas gratefully received - just trying to avoid replacing all the pipework!