Navien Error Code E788: Pump Failure
Warning: Your Navien boiler has detected a pump failure, which may cause system lockout and no heat.
How to Fix Navien Code E788
- Check your boiler's water level and top it off if necessary, but be careful not to overfill
- Listen for unusual noises from the pump, which could indicate a mechanical failure
- If the boiler is still under warranty, contact Navien's customer support for assistance
How to Reset Navien Code E788
- 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 E788 Mean?
The E788 error on your Navien boiler indicates a failure in the circulation pump. This pump is responsible for circulating hot water through your heating system. When it fails, your boiler won't be able to distribute heat, leading to a system lockout. This is a yellow hazard level because while it's not an immediate safety risk, it does require professional repair to restore heat.
Common Causes
- Worn out pump motor or bearings
- Clogged pump due to debris or air in the system
- Faulty pump control board or wiring
- Low water levels or air in the system causing pump cavitation
Diagnostic Steps
| If... | Check | Expected |
|---|---|---|
| Boiler is not heating | Water temperature at the boiler's outlet | Hot water (around 180°F/82°C) |
| Pump is not running | Pump's electrical connection for power and continuity | 24V AC power and continuity |
Applicable Navien Models
Source Documentation
Referenced in 6 official Navien technical manuals.
| Manual | Page | Reason | Action |
|---|---|---|---|
| NFB-H Installation & Operation Manual | 116 | Incorrect Gas Type Setting | Check DIP switch setting. |
| Navien NFC-H Installation & Operation Manual | 128 | Abnormal Gas Setting | Manual RESET (Start-up Wizard ) |
| Navien NCB-H Installation & Operation Manual | 130 | Incorrect Gas Type Setting | Check the supplied gas type and match the gas type setting on the PCB DIP switch. |
| Navien NFB-H Installation & Operation Manual | 116 | Incorrect Gas Type Setting | Check DIP switch setting. |
| Navien NHB-H Installation & Operation Manual | 119 | Incorrect Gas Type Setting | Check DIP switch setting. |
| Navien NPF Installation & Operation Manual | 128 | Abnormal gas type settings | This error occurs when the DIP switches are not set properly. ● Check if the DIP switch settings for the furnace’s gas type are set properly. |
Replacement Parts
| Part | OEM Number | Est. Cost | Where to Buy |
|---|---|---|---|
| Circulation Pump | N100000010 | — | Find Part |
| Pump Control Board | N100000011 | — | Find Part |
Related Codes on Same Models
Other codes that affect the same Navien model families as E788.
| 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 |