The boiler starts up at night despite both system controls being set to off and it not being cold enough for the system safety thermostat to operate, if I pressed the reset button it shut down, but restarted some time later: if I turned off the power the system reverted to correct operation for a while. I first noticed that during the daytime the boiler was running constantly despite the Room tmeperature being above the CH thermostat setting.

Ken P, December 2012