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Navien · Tankless water heater

E788 Gas type mismatch: DIP switch vs panel setting

Medium severity Navien NPE-2

What the control is telling you

The gas type on front-panel DIP switch 1 does not match the gas type stored in the panel. Expected right after changing DIP switch 1 during a conversion.

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

  • DIP switch 1 changed (gas conversion)
  • Panel gas setting not updated

Test and repair steps

  1. Confirm the gas supplied and the rating plate.
  2. Set DIP switch 1 OFF natural gas, ON propane (power off when changing).
  3. Power on; in the error screen press Back to open Gas Type Check in the Start-Up Wizard and select the gas type.
  4. On propane, accept the Gas Conversion Kit Required prompt. The error then clears and the unit fires.
  5. After any conversion, check CO2 or the low-fire offset pressure against the conversion tables.

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, 8.1, p.112. 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.