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Navien · Tankless water heater

E773 Wrong gas type detected

Critical severity Navien NPE-2Navien NPN

What the control is telling you

The unit detects that the gas connected does not match the gas type set at installation.

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; also Navien NPN non-condensing tankless water heaters: NPN-160U/180U/199U (universal, indoor or outdoor with vent kit) and NPN-120E/160E/180E/199E (outdoor only)

Likely causes

  • Wrong gas connected
  • Gas type DIP switch 1 wrong
  • Unit not converted with the Navien kit
  • Measuring tolerance (can trip with correct gas)

Test and repair steps

  1. Warning: wrong gas causes abnormal combustion and CO - shut the unit down until resolved.
  2. Check the rating plate against the gas supplied.
  3. Check front-panel DIP switch 1 OFF = natural gas, ON = propane.
  4. Make sure any conversion used the Navien conversion kit with the correct orifice.
  5. Parameter 16. Gas Connect Error Check Enable (default On) controls this check.
  6. Gas type and DIP setting correct but code still there? Phone Navien Technical Support, 1-800-519-8794.

Settings for these units

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Source: Navien NPE-A2/S2 User's Information Manual (20049624A), 5.2 Understanding Error Codes, p.18; Navien NPE-A2/S2 Installation Manual, 3.3, p.19; Navien NPN-U/NPN-E Installation Manual, 3.3, p.19. 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.