HVACopediaNavien · Combi boiler
E003 Ignition failure
What the control is telling you
The burner did not light (no flame proven) during the ignition attempts. NFC-H manual lists the reset type as: Manual reset.
Applies to: Navien fire-tube combi boilers, NFC-H series (NFC-250/200H, NFC-250/175H) and NCB-H combi boilers (NCB-250/150H, NCB-240/130H, NCB-240/110H, NCB-190/080H, NCB-190/060H)
Likely causes
- Main gas supply valve closed or gas supply interrupted
- Inlet gas pressure out of range
- Wrong gas type / orifice for the gas supplied
- Dirty or badly positioned ignition/flame detector electrode, poor ignition ground
Test and repair steps
- Make sure the main gas supply valve is open (the manual's listed remedy).
- Measure inlet gas pressure at full fire NG 3.5-10.5 in WC; LP 8.0-13.5 in WC (NCB-H) or 8.0-13.0 in WC (NFC-H).
- Confirm DIP SW2 #1 matches the gas supplied (OFF = natural gas, ON = propane) and the correct orifice is installed.
- Remove and clean the ignition/flame detector electrode; replace it if it cannot be cleaned, and check its gasket.
- Check the ignition ground wire is secure and has continuity to the casing.
- Check Service Status Info for repeated 2nd-10th ignition attempts to judge how often lighting is marginal.
- Reset from the front panel by pressing the Back button, then confirm the code clears.
- Code keeps returning? Phone Navien Technical Support, 1-800-519-8794.
Settings for these units
Minimum installation clearances (indoor) · Navien NCB-H
| Side | Minimum |
|---|---|
| Top | 9 in (229 mm) |
| Back | 0.5 in (13 mm) |
| Front | 4 in (100 mm) |
| Sides | 3 in (76 mm) |
| Bottom | 12 in (300 mm) |
Indoor wall-hung only; ambient must stay above 32°F (0°C).
Do not install on carpet; leave room for service.
Water quality limits (DHW and system fill) · Navien NCB-H
| Contaminant | Max allowed |
|---|---|
| Total hardness | 200 mg/l (12 grains/gallon) |
| Aluminum | 0.05 to 0.2 mg/l |
| Chloride | 250 mg/l |
| Copper | 1.0 mg/l |
| Iron | 0.3 mg/l |
| Manganese | 0.05 mg/l |
| pH | 6.5 to 8.5 |
| Sulfate | 250 mg/l (DHW table); 205 mg/l (fill table) |
| Total dissolved solids | 500 mg/l |
| Zinc | 5 mg/l |
| Chlorine (fill water) | 4 mg/l |
Scale damage from poor water is not covered by warranty.
Manual shows sulfate 250 mg/l on p.23 and 205 mg/l on p.29 - check local guidance.
- Minimum installation clearances (indoor) · Navien NFC-H
- Water quality limits (DHW and system fill) · Navien NFC-H
Models that show this code
7 models in Navien NCB-H, Navien NFC-H
Other codes on the same units
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Source: Navien NCB-H Installation & Operation Manual, 11.7 Understanding Error Codes, p.129-130; Navien NFC-H Installation Manual, 11.7 Understanding Error Codes, p.127-128. Summarized in our own words; check the original manual for your model.
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For licensed technicians. Gas, electrical and refrigerant work must be done by a qualified, licensed person. Shut off power and gas before servicing, never bypass a safety control, and follow the manufacturer’s manual for the exact model; it and local codes always take priority. HVACopedia is not affiliated with any manufacturer; brand and model names only identify the equipment.