My boiler keeps short cycling when the UFH (ground floor 5 zones) is demanding heat. Burner is on for 1 min and off for 3 mins constantly. I have CH (5 Rads) upstairs HW as well. Boiler is Potterton Tittanim 40kw. Boiler modulates perfectly when CH and HW are demading and burner remains constant. I have noticed that when the CH and UFH are demanding heat at same time that the flow to the UFH manifold remains constant and the burner remains on. There is a temp gauge installed on to the flow of the manifold and I have noticed it flactuates between 30 and 60 degrees when the UFH is demanding heat only and is short cycling. When the CH and UFH are demanding at the same time and the burner remains constant the temp on the manifold reads 60 degrees constantly. I have recently posted on here regarding my boiler overheating as the heat was not dispersin quick enough from the boiler and received some great information about an auto bypass which I have installed and this has helped the overheating issue. Just wondered how I can get my boiler to modulate correctly when the UFH is demanding heat. Do I have a electrical issue? Do I have a flow issue? Any help will be appreciated.