Hi, We mounted the trv on a new rad at the top horizontal, it's a Drayton liquid sensor type. It works fine if the radiator is cold. The radiator is always on as it's the main kitchen radiator so it's just set to 6 so I thought that means the valve should be open all the time. Problem is after about 30 mins the valve shuts, the radiator goes cold or luke warm and didn't seem to open until the pipes are cold again. Why is the valve closing when it's set to max? The temp in the kitchen is 19-20 with the valve set to 6 the max output. Have I got the wrong head do only some work horizontal? Thanks for any help.