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Navien · Boiler

E012 Flame loss

High severity Navien NHB-HNavien NFB-H

What the control is telling you

The flame went out during operation. Manual action: check gas, venting and the condensate trap.

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

Likely causes

  • Low or unstable gas pressure
  • Blocked or over-length vent / intake
  • Condensate trap empty, blocked or backing up
  • Dirty flame rod
  • Wrong orifice or combustion setting

Test and repair steps

  1. Check inlet gas pressure at maximum fire NG 3.5-10.5 in WC, LP 8.0-13.0 in WC.
  2. Inspect the exhaust and intake for blockage, snow, separated joints, and verify length/elbows are within limits (2 in: 65 ft, 3 in: 150 ft; 90° = 8 ft / 5 ft).
  3. Check the condensate line slopes down at least 1/4 in per ft, is not frozen, and the trap is filled with water.
  4. Clean the flame rod and check the Flame Loss count in Service Status Info.
  5. Check the air intake filter for lint/dust.
  6. Verify CO2 at low and high fire against the combustion table; at high fire never adjust the valve - check the orifice instead.

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Source: Navien NHB-H Installation and Operation Manual, 11.14 Understanding Error Codes, p.119; Navien NFB-H Installation Manual, 11.7 Understanding Error Codes, p.116; NHB-H User's Information Manual (V1.0 Apr 2024), 5.2, p.24. 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.