Rheem RTEX-18 Tankless Water Heater Error Codes
RTEX-18 Error Code Reference
Section titled “RTEX-18 Error Code Reference”Electric, 18 kW
| Error Code | Fault Description |
|---|---|
| C6 | Water flow sensor fault or insufficient flow rate |
| C8 | Inlet water temperature too cold or NTC1 thermistor fault |
| C11 | Thermistor (temperature sensor) fault |
| C13 | High-limit (ECO) safety switch tripped |