Oil burner shuts down after 20 to 30 minutes -restarts w/o reset till thermos satifies.it is a w/m wtgo4/riello f4o/b5. On a call for heat,the boiler and circ. Start,and the circ. Cycles as it should while the system is warming up.after the returns get warmer{maybe 20-30mins}the boiler drops out and restarts within seconds{after the 12sec.purge}soon after the thermos satisfies then shuts the circ and the boiler down.at this point the thermometer on the boiler is 160-170,press 18-20.could the riello be shutting down on time-out?what are soft lockouts. the system is 5 going on its6 yr. I think its always done it.just had the annual last week.the tech. said he heard some do that.maybe it is normal but I wonder?