Navien E594
Navien E594: EEPROM memory fault
Short answer
Navien E594 is an EEPROM fault: a problem with the memory chip on the control board that stores the heater's settings. It is listed for NPE-2 water heaters. Navien's manual says to contact technical support. A technician checks the board and its settings, and the board may need to be replaced or reprogrammed.
In this guide
The EEPROM is a small memory chip that keeps your heater's settings, even through power outages. E594 means the board cannot read or write that memory correctly.
The meaning and recommended action below come from Navien's User's Information Manual for NPE-2 condensing water heaters (NPE-180A2, NPE-210A2, NPE-240A2 and the S2 models). Navien technical support: 1-800-519-8794.
This code is listed for the current NPE-2 generation. The original NPE-A and NPE-S models do not have it.
What can cause it
- A power surge or electrical disturbance
- Moisture or damage on the control board
- A failing control board
What to do
- Press the Back button to reset once.
- If the code returns, contact your installer or Navien technical support.
- Consider a surge protector suited to the heater's power supply, especially in areas with frequent outages.
Before you call
Have the model number and serial number from the rating plate on the side of the unit ready, along with the date it was installed and the exact code. Navien asks for this information when you contact technical support, and your installer should be your first call for warranty service.
See every code on our Navien error codes page.
Common questions
Will I lose my Navien settings with E594?
The code means the memory has a problem, so settings may need to be checked or re-entered by a technician after repair.
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Other Navien codes
| Code | Meaning |
|---|---|
| E003 | Ignition failure |
| E004 | False flame detection |
| E012 | Flame loss |
| E016 | Heat exchanger overheat |
| E030 | Abnormal exhaust temperature |
| E031 | Burner overheating |
| E046 | Limit control (high limit switch) abnormal |
| E047 | Exhaust temperature sensor (thermistor) open or short |
| E060 | Dual venturi abnormal operation |
| E109 | Fan motor abnormal operation |
| E110 | Exhaust blockage (condensate blockage) |
| E407 | Hot water outlet temperature sensor open or short |
| E421 | Cold water inlet temperature sensor open or short |
| E432 | Cold water inlet 2 sensor open or short |
| E434 | Water adjustment valve fault |
| E438 | Circulation pump fault |
| E439 | Flow sensor fault |
| E441 | Second hot water temperature sensor open or short |
| E445 | Bypass mixing valve fault |
| E515 | Control board (PCB) abnormal operation |
| E517 | DIP switch setting fault |
| E593 | Front panel key fault |
| E594 | EEPROM (memory) fault |
| E615 | Input and memory fault |
| E736 | Cascade communication fault |
| E740 | Outdoor temperature sensor fault |
| E760 | Flushing or service alarm |
| E762 | Vent pipe not properly inserted |
| E773 | Using the wrong gas |
| E782 | Main panel communication fault |
| E785 | Flow switch or flow sensor fault (with AHU) |
| E788 | Gas type mismatch between board DIP switch and front panel |