I have a Potterton Netaheat 16/22 which was installed about 20 years ago on a fully pumped Y plan system. Some repairs recently and its working OK except the pump over - run seems to go on for ages (up to an hour). The boiler is not fitted with the optional high temperature thermostat that sits in the pocket alongside the normal operating one. Does it need an over - run? If so why is it now running for so long? Any ideas please?
