HVACopediaNoritz · Tankless water heater
14 Thermal fuse failure
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
- Warning: Find the cause of the overheat before replacing the thermal fuse.
- Turn off power, then check the thermal fuse wiring around the heat exchanger for continuity.
- Check water hardness; above 12 gpg (200 mg/L) treat or soften the water.
- Descale/flush the heat exchanger (see guide 'Descaling (flushing) the heat exchanger - Noritz').
- Check combustion gas pressure, venting and burner condition.
- Replace the thermal fuse if open and confirm normal operation.
Settings for these units
Indoor clearances (required and recommended) · Noritz NRCR
| Location | Required | Recommended (service) |
|---|---|---|
| Top | 12 in. (300 mm) | 3 in. (76 mm) above and below exhaust |
| Front | 4 in. (100 mm) | 24 in. (610 mm) |
| Sides | 3 in. (76 mm) | 8 in. (203 mm) |
Required clearances apply to both combustible and non-combustible materials.
Recommended space is for service and quick access to gas and water shut-offs.
Operation panel menu settings and defaults · Noritz EZ, Noritz NRCR
| Setting | Options | Default |
|---|---|---|
| Max Set Temperature (power off) | 100-140 F in 5 F steps; 37-48 C, 50-60 C | 120 F / 50 C |
| Recirc ON/OFF | ON / OFF | OFF |
| Recirc Mode | Always OFF, Always ON, Manual Timer, Auto Learning (NRCR) | Always OFF |
| Vacation Mode | Active / Inactive | Inactive |
| Flow Meter Alarm | 10-60 gal (5 gal steps), 70-100 gal (10 gal steps), OFF | Alarm OFF |
| Drain Water (power off) | Start / Cancel | Cancel |
| Scale Flushing (power off) | Start / Cancel | Cancel |
| Audible Alarm | ON / OFF | ON |
| Screen Lock | Active / Inactive (4-digit password) | Inactive |
| Units (first 10 min after power-up, power off) | [F/gal/ft] or [C/L/m] | [F/gal/ft] |
| Power Saving Dis. / Backlight | ON-OFF / Power Save ON-OFF | ON / Power Save ON |
| Brightness / Contrast / Touch Sound | Bright-Normal-Dim-Dark / -15 to +15 / ON-OFF | Normal / Standard / ON |
Setting 125 F (55 C) or higher needs Max Set Temperature raised first; the panel warns about scald risk.
Default Settings resets everything in Settings except Screen Lock (hold OK about 5 s).
- Water quality limits · Noritz EZ, Noritz NRCR
Models that show this code
8 models in Noritz NRC/NRCP, Noritz NRCR
Other codes on the same units
- 06 Low recirculation flow (warning only)
- 10 Abnormal combustion (NRCR, gas supply related)
- 11 Ignition failure (no flame detected)
- 12 Flame loss (repeated)
- 16 Abnormally high outlet temperature
- 20 High limit switch tripped
- 29 Condensate collector water level abnormal
- 061 Recirculation abnormality (sub-code of 06)
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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.