E003 Ignition failure

What the control is telling you

The burner did not light during the ignition attempt.

Applies to: Navien NPE-A2 (built-in recirculation) and NPE-S2 condensing tankless water heaters: NPE-150S2, NPE-180A2/S2, NPE-210A2/S2, NPE-240A2/S2

Likely causes

• Manual gas valve closed or gas supply interrupted
• Inlet gas pressure too low (undersized line, regulator, meter capacity)
• Gas type DIP switch 1 does not match the gas supplied
• Air in a new gas line

Test and repair steps

1. Make sure the manual gas shut-off valve to the unit and the main supply are fully open (manual's first action).
2. Measure inlet gas pressure at the pressure port with several high-flow fixtures open (max fire): 3.5-10.5 in. WC natural gas, 8.0-13 in. WC propane.
3. Check the gas line 3/4 in. connection, no 1/2 in. corrugated connector, meter capacity covers all connected appliances; Navien recommends the heater be the first appliance off the meter.
4. Confirm front-panel DIP switch 1 matches the gas (OFF = natural gas, ON = propane) and the rating plate.
5. On a new install, purge air from the gas line and retry.
6. Check Installer Menu > 1. Service Status Info for repeated 2nd/3rd/4th ignition counts.
7. Reset once with the Back button on the front panel and note whether the code returns.
8. Code back after a reset? Stay at the unit and phone Navien Technical Support, 1-800-519-8794.

Settings for these units

• Installation clearances (indoor / outdoor) · Navien NPE-2
• Water quality limits and flushing schedule · Navien NPE-2