This says more about me than any deficiency in the Evo system but I'm posting just to save any other potential headscratching. I was changing the batteries in an HR92 and following the instructions to turn the black plastic wheel inside the valve before dropping and locking the head back on. As I rotated the plastic wheel anticlockwise I must have exceeded the stop and it came off the valve body. Not a problem in itself but the axis of the body is not quite vertical so I duely placed it on and turned it clockwise to attach then turned it back again. The head sat on the wheel pin and properly cycled but of course the radiator couldn't properly shut off because of the skewed contact. Luckily there was no permanent damage but a slight cross thread caused a temporary problem. Regular members here will scoff but I also know I bought into the system after reading many posts on here and I guess new users are coming through all the time.