I am wondering what the controllers function is in hydronic floor heating? I have installed pex in the joist space's for the main floor. There is 5 separate loops for the main floor, 3 more to be added for the basement once I get it finished. Hence the 8 loop manifold with a 4 wire actuator for each loop. I am toying with the idea of putting a thermostat in each room to have individual control. My idea is to have power running to each thermostat on a open contact. When the contact closes it would call on the actuator to open the loop. When the actuator opens the loop it will close a contact calling for the pump to start etc. I am running a Navian CR-210A tankless hot water supply with a Navain heating box HDC-100. The heating box takes the place of the boiler and use's the hot water from the CR-210A. The heating box is closed loop type.