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Navien · Boiler

E109 Fan motor fault

High severity Navien NHB-HNavien NFB-H

What the control is telling you

The combustion fan is not reaching or holding the target speed. Manual action: check the fan and venting.

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

Likely causes

  • Fan wiring or hall sensor fault
  • Fan motor failure
  • Excessive vent restriction or blocked intake

Test and repair steps

  1. Run Test Mode > 1. Fan Motor; the fan should ramp up to top speed then back down.
  2. Compare Fan Target RPM with Fan Current RPM and Target/Current APS voltage in Status Info.
  3. Inspect venting and intake for blockage and confirm length/elbows are within limits.
  4. Clean the air intake filter.
  5. Warning: Power off, then check the fan connector and harness; replace the fan if it fails the test.

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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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