ferroli falcon locks out c.h.only

[tyson53]

ferroli falcon 9yr old,d.h.w ok heating gets to desired temp then shuts down as the radiators cool boiler attemps to start up then locks out (ie red light on)i then reset the boiler its ok for about 20 mins then the above happens again
thanks for any help /advice

[htg engineer]

it could be a few things, are the radiators getting too hot ? it could be over heating or it could be a faulty over heat stat.

Not familiar with the boiler, but does the burner/pilot light then go out ? could be a problem with the flame sensing electrode.

Or if it doesn't light, it could be a fault with the ignition, either the lead, spark generator or PCB