Navien Error Code E818: Abnormal return air- temp sensor operation for lower limit
How to Fix Navien Code E818
- Step 1: Check that the cold water supply to the unit is fully open.
- Step 2: If it's very cold outside, and you've only been using small amounts of hot water, try running a hot water faucet at a moderate flow for a few minutes to see if the error clears. This might warm the return line enough for the unit to restart.
- Step 3: If the error persists, contact a qualified HVAC technician to diagnose and repair the issue.
What Does Navien Error Code E818 Mean?
The E818 error code on your Navien tankless water heater indicates that the return water temperature sensor is reporting an abnormally low temperature. This sensor monitors the temperature of the water returning to the unit after it has circulated through your plumbing. If the return water is too cold, it can cause condensation inside the unit, which can lead to corrosion and damage. To prevent this, the unit shuts down and displays the E818 error. This is a protective measure to prevent damage to the unit. The sensor itself, the wiring, or the main control board could be at fault. It's important to address this issue promptly to avoid further problems and restore hot water service.
Common Causes of Navien Code E818
- Faulty return water temperature sensor (open or shorted)
- Loose or corroded wiring connections to the return water temperature sensor
- Defective main control board (PCB)
- Extremely cold incoming water temperature combined with low hot water demand
Applicable Navien Models
Source Documentation
This error code is documented in 1 official Navien technical manual.
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