hi all, hope someone can help. I've just installed a new greenstar 24ri boiler and have hit a small snag. The boiler is a replacement for an old potterton that after 20 odd years gave up the ghost. The new boiler fires up ok when hot water is required and will shut down when the set temp for the hot water is met, the problem occurs when central heating cuts in, it operates the mid position valve as it should and will heat the house fine but it wont shut down when the room temp stat is met. I have gone back to the programmer and manually switched off both hot water and central heating circuits and still the boiler runs. the only way to shutdown the boiler is to switch off the electrical supply to the whole system and then turn it back on to reset it. the boiler has a pump overrun [/b]