Hi, I have a problem with my Vokera excell 96 e. Recently i`ve noticed the boiler fires up for heating whether the timer (Randall 103 ) is switched to constant, Off or off on the timer. I`ve looked for a frost thermostat thinking it maybe this but cant see one near the boiler. I also turned the boiler to water only but it still fires up the heating. Can anyone help. Thanks John