Navien Error Code E594: Condensate Blockage
Warning: Your Navien boiler has detected a blockage in the condensate drain line. This could lead to water damage if not addressed promptly.
How to Fix Navien Code E594
- Locate the condensate drain line and follow it to the exit point, usually a floor drain or outside
- Check for any obvious blockages or kinks in the line
- If you find a blockage, try to clear it using a wet/dry vacuum or a plumber's snake. If you're unsure, contact a professional
How to Reset Navien Code E594
- Turn off the unit using the power button on the front panel.
- Turn off the gas supply valve.
- Turn off the circuit breaker supplying power to the unit. Wait 30 seconds.
- Restore power at the breaker, then open the gas valve.
- Turn the unit back on. If the error returns, the underlying issue needs repair.
Resetting clears the code from the display but does not fix the underlying fault. If the code returns after reset, proceed to the diagnostic steps above.
What Does Navien Error Code E594 Mean?
The E594 error on your Navien boiler indicates that the condensate drain line is blocked. Condensate is the byproduct of combustion, and it needs to be safely removed. When the drain line is blocked, water can back up and potentially cause damage to your boiler and surrounding areas. It's important to address this issue as soon as possible to prevent any further problems.
Common Causes
- Blockage in the condensate drain line due to mineral deposits or debris
- Kinked or crushed drain line
- Incorrectly installed or too small of a drain line
- Air in the system causing a blockage
Diagnostic Steps
| If... | Check | Expected |
|---|---|---|
| Water is present in the condensate neutralizer | Measure the resistance between the neutralizer and the ground | Less than 10 ohms |
| The boiler has been running for more than 30 minutes | Check the temperature of the condensate line | Close to the boiler's operating temperature |
Applicable Navien Models
Source Documentation
Referenced in 6 official Navien technical manuals.
| Manual | Page | Reason | Action |
|---|---|---|---|
| NFB-H Installation & Operation Manual | 116 | Abnormal EEPROM | Check the PCB. |
| Navien NCB-H Installation & Operation Manual | 130 | Abnormal EEPROM | Contact technical support at 1-800-519-8794. |
| Navien NFB-H Installation & Operation Manual | 116 | Abnormal EEPROM | Check the PCB. |
| Navien NFC-H Installation & Operation Manual | 127 | Abnormal operation: EEPROM | Alarm |
| Navien NHB-H Installation & Operation Manual | 119 | Abnormal EEPROM | Check the PCB. |
| Navien NPF Installation & Operation Manual | 128 | Abnormal EEPROM operation | This error occurs when the main controller does not operate properly. ● Turn off the furnace, turn it on again, and check if the furnace is operating properly. ● If this error occurs continuously, contact Technical Support at 1-800-519-8794. |
Replacement Parts
| Part | OEM Number | Est. Cost | Where to Buy |
|---|---|---|---|
| Condensate Neutralizer | N0301000000 | — | Find Part |
| Condensate Drain Line | — | — | — |
Related Codes on Same Models
Other codes that affect the same Navien model families as E594.
| Code | Description | Severity |
|---|---|---|
| E001 | Ignition Failure | Warning |
| E003 | Abnormal Ignition | Warning |
| E004 | False Flame Detection | Warning |
| E012 | Flame Loss | Warning |
| E016 | Overheating | Warning |
| E030 | Exhaust Overheat Sensor | Warning |
| E031 | Inlet Thermistor Open/Short | Warning |
| E046 | Outlet Thermistor Open/Short | Warning |
| E047 | DHW Thermistor Open/Short | Warning |
| E060 | Fan Motor Abnormality | Warning |