HVACopedia

Navien · Boiler

E480 DHW tank sensor not detected

Low severity Navien NHB-HNavien NFB-H

What the control is telling you

The indirect tank sensor is not read. Manual action: check sensor connections.

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

Likely causes

  • Tank sensor not connected to the TANK terminal
  • Broken wire or failed sensor
  • DHW Call Signal set to DHW Tank Sensor while an aquastat is used

Test and repair steps

  1. Check the tank sensor wiring at the TANK terminal.
  2. If the tank uses an aquastat, set DHW Operation > 3. DHW Call Signal to DHW Thermostat.
  3. Check Tank Sensor Temp in Status Info; replace the sensor if open.

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.