E003 Ignition failure

What the control is telling you

The burner did not light during the ignition attempts. Manual action: check the gas supply valve and the igniter.

Applies to: Navien NHB-H (NHB-055H/080H/110H/150H) and NFB-H fire-tube (NFB-175H/200H) condensing boilers

Likely causes

• Manual gas valve closed or gas supply interrupted
• Inlet gas pressure outside the allowed range
• Gas type DIP switch or orifice does not match the gas supplied
• Dirty or damaged igniter / flame rod, poor ignition ground
• Blocked air intake filter, vent or condensate trap

Test and repair steps

1. Make sure the manual gas valve is open and other gas appliances have gas.
2. Measure inlet gas pressure with the boiler at maximum fire (Special Operations > 2nd MAX): NG 3.5-10.5 in WC, LP 8.0-13.0 in WC (NHB-H spec table lists LP max 13.5 in WC).
3. Confirm DIP SW2 #1 matches the gas (OFF = NG, ON = LP) and that the correct orifice / conversion kit is installed for the gas and altitude.
4. Purge air from a new gas line before the first start (the manual has you run space heating until it shuts down from lack of gas, then restart).
5. Warning: Turn off power and gas. Remove and clean the igniter and flame rod; replace if they cannot be cleaned, and check the gasket.
6. Check the ignition ground wire is tight to the casing and has continuity.
7. Check the air intake filter, vent terminations and condensate trap (filled with water and draining).
8. Check the ignition attempt counters in Service Status Info, then verify CO2 against the combustion table after repairs.

Settings for these units

Installation clearances (indoor) · Navien NHB-H

Bracket gives 5/8 in (16 mm) from the wall; studs at 16 in on centre.

Common vent installs: 36 in above the top and 24 in in front are recommended for service.

Installation clearances (indoor) · Navien NFB-H

Do not install on carpet; indoors only.

Remove the wood pallet and refit the 6 screws to keep the cabinet airtight.

Models that show this code

6 models in Navien NHB-H, Navien NFB-H

Other codes on the same units

• E001 Heat exchanger overheat
• E004 False flame detected
• E012 Flame loss
• E016 Heat exchanger overheat (check flow / system filters)
• E030 Exhaust overheat
• E031 Burner overheat
• E046 Heat exchanger thermistor fault
• E047 Exhaust thermistor fault