Low water pressure Manual reset
The E302 error code on Navien boilers indicates low water pressure manual reset. Symptoms include the system displays e302 low water level error is generated if water pressure is 0.5 bar (7.3 psi) or.
Navien E302 means: low water pressure manual reset. The usual causes are is there a leak inside the or repair the leak. You can safely reset the boiler once — if E302 returns, do not keep resetting. A qualified heating engineer should diagnose the root cause.
What Does E302 Mean
The E302 code is shown by the boiler’s control board when it detects low water pressure 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 |
|---|
| the system displays E302 Low water level error is generated if water pressure is 0.5 bar (7.3 psi) or |
Common Causes
Causes documented in 2 technical sources.
| Cause |
|---|
| Is there a leak inside the |
| Repair the leak |
Safety Warning
E302 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
Check the boiler pressure gauge — normal operating pressure is 1.0-1.5 bar (15–22 psi) when cold
Inspect all visible pipework, radiators, and valves for signs of leakage
Check the pressure relief valve discharge pipe — if water is dripping, the PRV may be faulty or the expansion vessel has failed
Test the expansion vessel — with the system cold and drained, check the Schrader valve on the vessel
air should escape at the correct pre-charge pressure (typically 0.75-1.0 bar, 11–15 psi)
Inspect the pressure sensor connections
Check automatic air vents for signs of weeping
How to Fix It
Repressurise the system via the filling loop to 1.0-1.5 bar (15–22 psi)
repair any identified leaks
if the expansion vessel has lost its charge, re-pressurise it with a pump (or replace if the diaphragm has failed)
replace the pressure relief valve if it is passing water
replace the pressure sensor if it is giving incorrect readings. Note: frequent pressure loss indicates an underlying leak that must be found and repaired
Check if the input water pressure sensor is wet for any reason, including leakage.
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 E302:
| Model Family | Output Range | Frequency |
|---|---|---|
| All Navien models | — | Possible |
Frequently Asked Questions
Repressurise the system via the filling loop to 1.0-1.5 bar (15–22 psi). According to the technical documentation, this is the first check on the list for E302.
E302 is not classified as a high-severity fault, so the boiler can be reset once. If E302 comes back, stop resetting: the underlying cause is still there and needs a qualified heating engineer.