HVACopedia

Navien · Boiler

E110 Exhaust blockage

High severity Navien NHB-HNavien NFB-H

What the control is telling you

The control detected a blocked exhaust/air path. Manual action: check exhaust venting. The User's Information Manual adds that a clogged air intake filter also causes code 110.

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

Likely causes

  • Air intake filter clogged with dust or lint
  • Blocked exhaust or intake termination (snow, ice, debris, nests)
  • Vent too long or too many elbows
  • Condensate backing up into the vent

Test and repair steps

  1. Warning: Turn off and unplug the boiler before opening the cover.
  2. Remove the air intake filter (top left inside the cabinet), rinse with clean water, dry and refit.
  3. Check both terminations are clear and at least 12 in above grade/snow line.
  4. Confirm vent length and elbows 2 in max 65 ft with up to 6 elbows, 3 in max 150 ft with up to 8 elbows (90° elbow = 8 ft on 2 in, 5 ft on 3 in).
  5. Check horizontal runs slope up 1/4 in per ft toward the termination and the condensate drain is clear.
  6. Check APS voltage readings in Status Info after repairs.

Settings for these units

Save it for the next call

Star this code in the HVACopedia app and keep the whole library on your phone for jobs with no signal.

Open the app

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.

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.