HVACopediaNavien · Tankless water heater
E031 Burner overheating
What the control is telling you
The burner high-temperature protection tripped.
Applies to: Navien NPE-A2 (built-in recirculation) and NPE-S2 condensing tankless water heaters: NPE-150S2, NPE-180A2/S2, NPE-210A2/S2, NPE-240A2/S2
Likely causes
- Burner overheat (burner high limit fuse)
- Combustion or air supply problem
Test and repair steps
- Warning: do not keep resetting a burner overheat - check the cause first.
- Inspect the intake and exhaust for blockage and clean the air intake filter.
- Check CO2 at low and high fire against the table in the installation manual (Appendix 8.1).
- Only fix given phone Navien Technical Support, 1-800-519-8794.
Settings for these units
Installation clearances (indoor / outdoor) · Navien NPE-2
| Side | Indoor | Outdoor |
|---|---|---|
| Top | 9 in. (229 mm) | 36 in. (900 mm) |
| Back | 0.5 in. (13 mm) | 0.5 in. (13 mm) |
| Front | 4 in. (100 mm) | 24 in. (600 mm) |
| Sides | 3 in. (76 mm) | 3 in. (76 mm) |
| Bottom | 12 in. (300 mm) | 12 in. (300 mm) |
Vent clearance to combustibles is 0 in.
Outdoor: use the Navien Outdoor Vent Kit; keep 3 ft from an eave to the top of the vent terminals; mild climates only.
Water quality limits and flushing schedule · Navien NPE-2
| Hardness | grains/gal (mg/L) | Treatment | Flush frequency |
|---|---|---|---|
| Soft | 0-4 (0-60) | None | None |
| Moderately hard | 4-7 (61-120) | None required | Once a year |
| Hard | 7-9 (121-160) | Softener or Navien PeakFlow recommended | Once a year |
| Very hard | 9-12 (161-200) | Softener or PeakFlow highly recommended | Residential once a year; commercial twice a year |
| Extremely hard | >12 (200) | Softener or PeakFlow required | - |
Other max levels: hardness 200 mg/L, chloride 250, copper 1.0, iron 0.3, manganese 0.05, sulfate 250, TDS 500, zinc 5, chlorine 4 mg/L; aluminum 0.05-0.2 mg/L; pH 6.5-8.5.
Flushing is advised when no treatment device is installed; use white vinegar or a tankless descaler.
Models that show this code
7 models in Navien NPE-2
Other codes on the same 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.
Source: Navien NPE-A2/S2 User's Information Manual (20049624A), 5.2 Understanding Error Codes, p.17. 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.