HVACopediaNavien · Boiler
E031 Burner overheat
What the control is telling you
NFB-H only. The burner temperature protection opened. Manual action: check the burner temperature fuse.
Applies to: Navien NFB-H fire-tube condensing boilers (NFB-175H/200H)
Likely causes
- Burner temperature fuse / high limit open
- Combustion problem overheating the burner area (blocked vent or heat exchanger, wrong orifice or CO2)
- Loose connector on the burner limit
Test and repair steps
- Warning: Turn off power and gas before opening the cabinet.
- Check the burner temperature fuse / burner high limit and its wiring connector for continuity.
- Check HTL Input Status in the Input/Output Status menu.
- Before replacing a fuse, find why it opened: inspect the vent and intake for blockage and check the burner and heat exchanger.
- Verify the orifice matches gas and altitude (NG 4.8/7.90, NG high altitude 5.05/8.4, LP 3.90/6.00) and check CO2 at low and high fire.
- Manual gives only the one-line action; contact Navien technical support if the cause is not found.
Settings for these units
Installation clearances (indoor) · Navien NFB-H
| Side | Minimum clearance |
|---|---|
| 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) |
| Vent to combustibles | 0 in |
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
2 models in Navien NFB-H
Other codes on the same units
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Source: Navien NFB-H Installation Manual, 11.7 Understanding Error Codes, p.116. Summarized in our own words; check the original manual for your model.
Homeowner looking at this code? See what it means for you and when to call a technician.
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.