radiators come on now and then by them selfs?

your hot water thermostat is faulty and the boiler to protect itself is running the pump to remove heat from the heat exchanger

serpen66
July 2010

I don't know your particular boiler, but I would suggest one of two things:
1: Electrical fault in internal/external controls allowing heating to come on (unlikely but possible).

2: Your boiler has a water 'preheat' function, this (as it suggests) pre-heats the domestic heat exchanger so the hot water is about as 'instant' as it can be.

If this is the case (likely suspect), then the boiler diverter valve would be at fault, it could be allowing the water designed to pre-heat the domestic water to 'leak' through the diverter into the heating system thus never satisfying the domestic pre-heat, and making the radiators hot.

Carefree
July 2010