So, upstairs rads closed and all downstairs rads get hot except for the furthest one. Reopened upstairs and now the downstairs ones are cooling down. How can they be a blocked pipe?
Thanks Paul, I should state that all rads are open and boiler has been on since 16:00. It heats the water then turns off, upstairs are hot but downstairs cold. Downstairs will only start to warm if I shut the upstairs ones completely.
We have a Potterton Performa combination boiler that has had the following replaced in the last week; pump, diverter valve, PRV, hot water heat exchange, central heating heat exchange. We have also had the system flushed and I have ensured again there is no air in the rads.
Upstairs is toasty...