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Navien · Combi boiler

E351 Auto feeder (make-up water) valve fault

High severity Navien NCB-HNavien NFC-H

What the control is telling you

The automatic fill could not restore system pressure: on NCB-H the code appears when water replenishment is not finished within 5 minutes and needs a manual reset. NFC-H manual lists the reset type as: Manual reset.

Applies to: Navien fire-tube combi boilers, NFC-H series (NFC-250/200H, NFC-250/175H) and NCB-H combi boilers (NCB-250/150H, NCB-240/130H, NCB-240/110H, NCB-190/080H, NCB-190/060H)

Likely causes

  • Make-up water supply closed or low
  • System leak or relief valve discharging
  • Auto-fill valve fault
  • Auto-fill pressure set too high for supply pressure

Test and repair steps

  1. Make sure the make-up water supply valve to the boiler is open.
  2. Check the system and the pressure relief valve for leaks/discharge.
  3. Check Status Information > 16. Water Pressure and the Auto-Fill Pressure parameter (NCB-H 12-30 psi, NFC-H 12-50 psi, default 12 psi).
  4. Check Input/Output Status > 13. Fill Valve Status.
  5. Reset from the front panel by pressing the Back button, then confirm the code clears.
  6. Code keeps returning? Phone Navien Technical Support, 1-800-519-8794.

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Source: Navien NCB-H Installation & Operation Manual, 11.7 Understanding Error Codes, p.129-130; Navien NFC-H Installation Manual, 11.7 Understanding Error Codes, p.127-128. 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.