Hello all im new to this forum and looking for some help that would be greatly appreciated. Ive recently had an extension and had wet under floor heating on a dual manifold with pump installed into a 25square meter area also had two additional rads installed all running off a vaillant ecotec plus 837 combi boiler.The system has two motorised valves controlled by room stats and a digital programmer. My problem is that when the central heating is running independently the two new rads in the ground floor extension take forever to warm up and when the underfloor heating is run independently it causes the boiler to overheat and shut down after only a minute or so it will continue to cycle on and off without the ufh reaching temp. If both rads and ufh is run simultaneously the boiler does not cycle. All valves on the uhf are open to the correct settings its as if I don't have sufficient flow through the boiler which im guessing at. ive turned the pump on the uhf to max to no avail also ive tried opening the flo valves wide open and also filled the uhf with a hose trying to release any locked air which wasn't the case. Ive also stipped the central heating pump to make sure it wasn't gunked up which it wasn't and it is spinning freely .Hopefully I haven't made it sound to confusing and any words of wisdom would be welcome . Thanks