This is really a question about designing a mixed system and how to control it.
I am planning to replace the existing DHW & CH boiler with a condensing combi. Existing radiators will be replaced on the ground floor except for the kitchen, ground floor toilet and utility room where a wet underfloor system is desirable. First floor radiators will also be replaced except for the bathroom where a towel rail will be installed together with wet underfloor heating.
What are the problems associated with such a mixed design?
In particular, how do I manage the earlier warm-up requirement of rooms using underfloor heating to compensate for the thermal lag of such systems especially when it it is common practice to use the cooler CH return to the boiler to drive the underfloor system?
Thanks,
ric