Navien furnace shows E030 and will not operate, often after power issues

Safety: Turn off power at the breaker before accessing control boards.

• Inspect wiring harnesses: Remove the front cover and locate the main PCB and display/control panel connections. Ensure all multi-pin connectors are fully seated and locked. Look for signs of corrosion or burnt pins.
• Check for moisture: Inspect the control area for signs of water intrusion or condensation. If moisture is present, identify and correct the source (leaking piping, vent, or condensate line) and allow the board area to dry completely.
• Verify grounding: Confirm that the furnace is properly grounded according to Navien installation instructions. Loose ground connections can cause communication errors.
• Power cycle: Turn the breaker off for at least 5 minutes, then restore power to reset the electronics. If E030 clears and does not return, it may have been a transient fault.
• Board replacement: If E030 persists, the main PCB or display board is likely defective. Replacement should be performed by a Navien-authorized technician to ensure correct programming and safe operation.