Ignition Failure
The boiler has failed to ignite — manual reset required. The most common Navien fault code. On Navien boilers, a frozen condensate pipe in winter is a common cause.
Code 003 in winter on Navien boilers is commonly caused by a blocked condensate pipe. Navien describes this as 'exhaust blockage' — see code 110.
Step-by-Step Fix Guide
-
Step 1
Check gas supply — try other gas appliances
-
Step 2
In cold weather, check the condensate pipe for ice and thaw with warm water
-
Step 3
Press the reset button on the boiler
-
Step 4
If fault persists, call a Gas Safe engineer to inspect the ignition system
Work on gas appliances must be carried out by a Gas Safe registered engineer. The steps above cover safe checks a homeowner can perform - any internal component replacement requires a qualified professional. If in doubt, always call an engineer.