Can anyone help please? I recently changed a radiator in our kitchen and all was going well until I made a silly mistake. When refilling the system via the loop I thought I had closed the tap and turned to bleed the new rad only to realise, too late, that I had left the refill tap open. There followed the most horrendously loud venting. Immediately after this I was unable to re-pressurise the system until I turned a green knob marked "3 bar" (I've since found out that this knob actually lowers the pressure on a pressurised system). The boiler is an Ariston Euro Combi styx. The immediate problem is that now there is no hot water passing through the central heating. The boiler fires up and cuts out at between 60 and 70c. I've been up in the attic (live in a bungalow) and it seems that there is some sort of blockage stopping the heated water from travelling through the pipework. I've bled the pump in the boiler and even closed all the radiators and drained the system down but to no avail. Has anyone any idea as to what the problem is, bearing in mind that it all worked ok until the system vented when the pressure went of the scale. All suggestions will gratefully received.