HVACopediaNoritz · Tankless water heater
10 Abnormal combustion (NRCR, gas supply related)
What the control is telling you
The NRCR training deck lists code 10 together with 90 as 'abnormal combustion' caused by an improperly sized gas line. The deck gives no other detail for 10.
Applies to: Noritz NRCR92 / NRCR111 (NRCR Pro)
Likely causes
- Undersized gas line or gas meter
- Water or debris in the gas line
- Earthquake safety shutoff valve restricting gas
Test and repair steps
- Measure inlet gas pressure at low, moderate, high and worst-case demand; NG must stay 3.5-10.5 in. WC and LP 8-14 in. WC.
- Check the gas line size against the gas sizing table in the installation manual (see Specs); a 1/2 in. line only works with 8 in. WC or higher initial pressure.
- Check the meter size and look for water/debris or a restricting earthquake valve in the supply.
- Also check intake/exhaust and condensate drain as for code 90.
- If the code persists, contact Noritz technical support (866-766-7489).
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
2 models in Noritz NRCR
Other codes on the same units
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Source: Noritz NRCR Pro training (NRCR92/NRCR111, Printable V3), Gas line conditions, p.20. 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.