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Navien · Combi boiler

E001 Heat exchanger overheat

High severity Navien NCB-HNavien NFC-H

What the control is telling you

The heat exchanger temperature went over its limit and the burner was shut down. NCB-H calls it 'Heat Exchanger Overheat', NFC-H 'heat exchanger over temperature'. NFC-H manual lists the reset type as: Manual reset / Auto 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

  • Low or no water circulation through the heat exchanger (air in system, closed valves, pump problem)
  • Clogged space-heating return filter/strainer
  • Scale build-up inside the heat exchanger

Test and repair steps

  1. Reset from the front panel by pressing the Back button, then confirm the code clears.
  2. Confirm system pressure and that all heating isolation valves are open; purge air (Installer menu 8. Air Purge Mode > SH pipe air purge).
  3. Check the boiler pump runs (Installer menu 6. Test Mode > 2. Boiler Pump).
  4. Clean the space-heating return water filter if heating performance has dropped.
  5. If it repeats, flush the heat exchanger (see E016).
  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.

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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.