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Navien · Boiler

E004 False flame detected

High severity Navien NHB-HNavien NFB-H

What the control is telling you

The control sees a flame signal when there should be no flame. Manual action: check the electrical ground.

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

Likely causes

  • Poor or missing electrical ground
  • Contaminated, wet or shorted flame rod
  • Gas valve not closing fully (flame present after shutdown)

Test and repair steps

  1. Verify the boiler is plugged into a properly grounded outlet, or if hard-wired that ground is not taken from gas or water piping.
  2. Check the ignition ground wire at the casing and test ground continuity with a meter.
  3. Check polarity of the power supply connection.
  4. Read the Flame Value in Status Info 70 or less means flame on, 175 or more means flame off. A low value with the burner off confirms a false signal.
  5. Warning: Power off. Inspect and clean the flame rod and its wire; replace if damaged.
  6. Warning: If flame stays on after the call ends, shut the manual gas valve and replace the gas valve.

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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.

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.