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Control board fault: tankless water heater / continuous flow hot water system codes by brand
The main control board detected an internal error.
| Brand | Code | Meaning | What you can do |
|---|---|---|---|
| Rinnai | 70 | Control board (PCB) failure | Safe checks first, then a pro |
| Navien | E515 | Circuit board fault | Safe checks first, then a pro |
| Navien | E593 | Front panel button fault | Call a pro |
| Navien | E594 | Memory chip (EEPROM) fault | Call a pro |
| Navien | E615 | Input and memory fault | Call a pro |