I recently had a new Sta Rite SR400HD installed as a replacement to my old non-functioning Hayward H400 pool heater. After the intial install and firing up the heater, the fan turns on and the heater begins to operate for about 30 seconds and then it turns off a the Service Heater light comes on. The heater is new and has never been used. Any ideas on why the service heeater light is coming on?