This hydraulic separation technique to be used avoids low loss headers and also other gumph required for underfloor heating. It’s not ideal due to space constraints but gives the overall theory. Understanding how to set this up is important. You want to balance the flow rate with the mixing valve fully open on max demand and adjust the bypass tee simultaneously with the pump speed until roughly Dt 20 (for gas boilers) is reached on the primary and Dt 7 aprox. on the secondary UFH side. You will also require a balancing valve on the flow to this circuit.