I have a small custom pool that was built in Sept 2014. We have the Pentair Mastertemp 400 heater. In December the heater quit working and the Pentair tech came out and said the Thermal Regulator was bad and they replaced it. Yesterday our heater stopped working again and the Pentair rep came back out today. He said the Thermal Regulator was bad again. Is this normal? Has anyone else had this issue? Any ideas of why this would keep happening?