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Noritz · Tankless water heater

14 Thermal fuse failure

High severity Noritz NRC/NRCPNoritz NRCR

What the control is telling you

The thermal fuse around the heat exchanger/combustion chamber has opened because of overheating. The NRCR deck lists 14 among the codes caused by hard water and scale.

Applies to: Noritz NRC/NRCP and older non-premix, and NRCR

Likely causes

  • Scale build-up in the heat exchanger from hard water
  • Poor combustion overheating the combustion chamber
  • Failed thermal fuse or broken wiring

Test and repair steps

  1. Warning: Find the cause of the overheat before replacing the thermal fuse.
  2. Turn off power, then check the thermal fuse wiring around the heat exchanger for continuity.
  3. Check water hardness; above 12 gpg (200 mg/L) treat or soften the water.
  4. Descale/flush the heat exchanger (see guide 'Descaling (flushing) the heat exchanger - Noritz').
  5. Check combustion gas pressure, venting and burner condition.
  6. Replace the thermal fuse if open and confirm normal operation.

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Source: Noritz Residential Level 2 Maintenance & Troubleshooting (NRC/NRCP and older, R2 V1), 14, 16, 20 error codes, p.8; Noritz NRCR Pro training (NRCR92/NRCR111, Printable V3), Poor water quality issues, p.32. 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.