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Navien · Boiler

E047 Exhaust thermistor fault

Medium severity Navien NHB-HNavien NFB-H

What the control is telling you

The exhaust temperature sensor reading is abnormal. Manual action: check the thermistor connector.

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

Likely causes

  • Loose or corroded connector
  • Damaged wire
  • Failed exhaust thermistor

Test and repair steps

  1. Warning: Turn off power before removing the front cover.
  2. Reseat the exhaust thermistor connector(s) (the control has Exhaust thermistor 1 and 2) and inspect wiring.
  3. Check Exhaust Temp in Status Info for a believable value.
  4. Replace the thermistor if the fault returns.

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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.