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Navien · Boiler

E031 Burner overheat

High severity Navien NFB-H

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

  1. Warning: Turn off power and gas before opening the cabinet.
  2. Check the burner temperature fuse / burner high limit and its wiring connector for continuity.
  3. Check HTL Input Status in the Input/Output Status menu.
  4. Before replacing a fuse, find why it opened: inspect the vent and intake for blockage and check the burner and heat exchanger.
  5. 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.
  6. Manual gives only the one-line action; contact Navien technical support if the cause is not found.

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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.

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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.