The invention relates to a hydronic heating/cooling system. In the system, liquid is led along a main supply pipe (1) to a supply manifold (2) and distributed in the manifold into heating loops (3). The heating loops (3) return to return manifold (4). At least one of the manifolds (2, 4) has actuators (6) for controlling the flow in the heating loops (3). At least one loop is designated to be a bypass loop. The actuators (6) in the loops (3) are monitored and it is ensured that the actuator (6) of the bypass loop is open if all the other actuators (6) are closed.