Navien Error Code E311: Abnormal water level

How to Fix Navien Code E311

1. Step 1: Check the condensate drain line (usually a white PVC pipe) for any visible kinks, clogs, or obstructions. Clear any blockages you can safely reach.
2. Step 2: Try power cycling the unit by turning it off at the breaker for a few minutes, then turning it back on. This may reset the sensor.
3. Step 3: If the error persists after these steps, contact a qualified HVAC technician to diagnose and repair the issue.

How to Reset Navien Code E311

1. Turn off the unit using the power button on the front panel.
2. Turn off the gas supply valve.
3. Turn off the circuit breaker supplying power to the unit. Wait 30 seconds.
4. Restore power at the breaker, then open the gas valve.
5. 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 E311 Mean?

The E311 error code on your Navien tankless water heater indicates that the unit's internal sensors have detected an abnormal water level. This usually means either the water level is too high or too low within the tankless unit itself. This is a safety mechanism to prevent the unit from running dry (overheating the heat exchanger) or from overflowing and damaging internal components. When this happens, the unit will lock out and stop producing hot water until the issue is resolved. This error can be triggered by a variety of factors, most commonly related to water flow, sensor issues, or problems with the unit's drain system. Because tankless units rely on precise water flow and level detection, it's important to address this issue promptly. Ignoring it could lead to further damage to the heat exchanger, pump, or other components. While some causes are simple to address, others require a qualified technician to diagnose and repair.

Common Causes

• Blocked or restricted condensate drain line, causing water to back up.
• Faulty water level sensor providing incorrect readings.
• Air trapped inside the unit preventing accurate water level detection.
• Malfunctioning pump not circulating water properly.
• Scale buildup inside the heat exchanger restricting water flow.

Diagnostic Steps

Replacement Parts

Related Codes on Same Models

Other codes that affect the same Navien model families as E311.