Managing heating w/ 2 zones - diff flow temps in each zone?

[joncox]

I have a Vaillant 618 and Unistor cylinder run as an S Plan, controlled by a VR65 and VRC 430. All works very well.

I'm thinking about having the ground floor rads removed and replaced by wet underfloor heating run off this system (mix of new to-be-screeded floors and to-be-insulated suspended floor).

I understand I would need the heating split into 2 zones (ground floor and upper floors), and the VR65 replaced by a VR61 mixing unit.

How, though, does a boiler simultaneously serve two zones when each zone requires a different flow temp (low for UFH, high for rads?).

many thanks

Jon

 

[Boilerman2]

The UFH will incorporate a Thermostatic mixing valve to keep the loop temeprature at about 50*c, whereas the Radiator Cct will operate at Boiler flow temp around 70*c

 

[joncox]

I thought it had to be a simple answer. Many thanks!