we installed a Rheem tankless hot water heater in April 30, 2008. We replaced the PCB board on Sept 8, 2010. There was no hot water on October 12, 2010 and it was reset. On October 23, 2010 when there was no hot water, the service man cleaned inside, checked fuses, tested the unit - working well. July 12, 2011 no hot water - reset. August 10, 2011, no hot water - waiting for the service person.