Before calling service technician, open following link for Rheen troubleshooting resources and possible error code help plus link to Rheem chat:
http://waterheatertimer.org/Troubleshoot-Rheem-Tankless-water-heater.htmlTypically, error codes are start-point for troubleshooting.
Error 76 is communication fault with remote control, which can be bad remote, bad wire, bad wiring connection, or bad part inside tankless.
C4 is oxygen sensor problem or bad venting.
More than 1 error code, or mixed error codes can indicate problem such as bad PC board -or- PCB.
×