Hi and thanks for your advice in advance. I have a potterton Performa He and when I put the heating on a couple of days ago the rads downstairs were cold. I bled all radiators and then turned them all off and starting downstairs tried switching them on one at a time to see if they got hot. After a while one at a time they did so I tried to put a few on downstairs and they went cold again. I checked the pressure and raised it with the loop thing, there seemed to be a lot of air come from the boiler and then the rads started to get hot. Great I thought then after about 10 mins that rads went cold again ( all over now) including the upstairs? The pressure has now raised a bit to high and am unsure how to reduce? Not sure what to do now? Any help please?