Abnormal Auto feeder valve (make-up water) Manual RESET
The E351 error code on Navien boilers indicates abnormal auto feeder valve (make-up water) manual reset. Symptoms include if water is supplied by auto feeder valve open over 5 minutes, the error(e351) is detected and displayed on the, front panel. if this occurs, the boiler initiates shutdown.
Navien E351 means: abnormal auto feeder valve (make-up water) manual reset. The usual causes are leaking in unit, defective auto feeder or defective heat. You can safely reset the boiler once — if E351 returns, do not keep resetting. A qualified heating engineer should diagnose the root cause.
What Does E351 Mean
The E351 code is shown by the boiler’s control board when it detects abnormal auto feeder valve (make-up water) manual reset. The boiler then stops instead of continuing to run in that condition: the code is the appliance reporting a problem, not proof that the boiler is broken.
| What you see on the boiler |
|---|
| If water is supplied by auto feeder valve open over 5 minutes, the error(E351) is detected and displayed on the |
| front panel. If this occurs, the boiler initiates shutdown. |
Common Causes
Causes documented in 2 technical sources.
| Cause |
|---|
| Leaking in unit |
| Defective auto feeder |
| Defective heat |
| Water leaks through the condensed water hose due to a defective heat exchanger. |
| Pipe leaks |
| Frequent water filling can occur due to leakage of pipe. Check the leakage on the |
Safety Warning
E351 involves electrical or pressure-related components. Do not attempt repairs without proper qualifications. Ensure the boiler is electrically isolated before any inspection. If you notice water leaks, unusual sounds, or pressure anomalies, contact a qualified heating engineer immediately.
Parts & Prices
Prices shown are indicative. Actual prices and availability vary by region.
Step-by-Step Diagnosis
Note the original fault code that caused the lockout
Investigate and resolve the underlying cause before resetting
Check the fault history in the boiler's diagnostic menu
Do not repeatedly reset without investigation — repeated lockouts indicate a persistent problem
How to Fix It
Resolve the underlying fault first
reset the boiler by pressing the reset button (typically hold for 3-5 seconds)
if the boiler locks out again within a short period, do not continue resetting — call a qualified engineer
Check if water leaks due to a defective heat exchanger.
Check if water leaks from the heating pipe.
Check leaking in unit
Refer to the Navien service documentation for the detailed procedure. Only a qualified engineer should carry out these repairs.
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Affected Models
Navien models that can display fault code E351:
| Model Family | Output Range | Frequency |
|---|---|---|
| All Navien models | — | Possible |
Frequently Asked Questions
Resolve the underlying fault first. According to the technical documentation, this is the first check on the list for E351.
E351 is not classified as a high-severity fault, so the boiler can be reset once. If E351 comes back, stop resetting: the underlying cause is still there and needs a qualified heating engineer.