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Navien · Tankless water heater

E004 False flame detection

Medium severity Navien NPE-2

What the control is telling you

The control sees a flame signal when the burner should be off.

Applies to: Navien NPE-A2 (built-in recirculation) and NPE-S2 condensing tankless water heaters: NPE-150S2, NPE-180A2/S2, NPE-210A2/S2, NPE-240A2/S2

Likely causes

  • Poor or missing electrical ground
  • Flame rod / control fault

Test and repair steps

  1. Make sure the power cord is plugged into a properly grounded outlet (manual's listed action).
  2. If hard-wired, confirm the green ground is connected to a real ground - not to gas or water piping (plastic pipe or dielectric unions break the ground path).
  3. Reset once with the Back button on the front panel and note whether the code returns.
  4. Check Menu > 2. Status Information > 12. Flame Valve (flame detection AD value) with the burner off.
  5. Code back after a reset? Stay at the unit and phone Navien Technical Support, 1-800-519-8794.

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Source: Navien NPE-A2/S2 User's Information Manual (20049624A), 5.2 Understanding Error Codes, p.17. 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.