overheating trianco combi oil boiler?

boiler limit stat trips when on the hot water heating side. Overrun stat and tank stat are both new also flowswitch is new and working correctly Still getting volts at terminal 2 which is holding on the relay untill the boiler limit stat switches out the burner. I don't know where the volts are coming from to keep the relay in even though all the stats are working. I have been using temp probes to track temp operation. I have been onto the Trianco technical dept and they are stumped. Anybody get any ideas?????
Thanks