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Navien · Boiler

E788 Incorrect gas type setting

High severity Navien NHB-HNavien NFB-H

What the control is telling you

The gas type setting is wrong. Manual action: check DIP switch setting.

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

Likely causes

  • DIP SW2 #1 does not match the gas supplied
  • Gas conversion done without changing the DIP switch

Test and repair steps

  1. Warning: Power off before changing DIP switches.
  2. Set DIP SW2 #1 OFF for natural gas, ON for propane, matching the rating plate and conversion label.
  3. Make sure the orifice matches the gas (the LP orifice comes in the Propane Gas & High Altitude Conversion Kit).
  4. Check Gas (NG/LPG) in Status Info, then verify CO2 per the combustion table.

Settings for these units

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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.