HVACopediaNoritz · Tankless water heater
91 Gas conversion not done correctly
What the control is telling you
EZ/NRCR: the unit's gas conversion was not completed correctly.
Applies to: Noritz EZ111/EZ98/EZ71 and NRCR111/NRCR92
Likely causes
- LP orifice installed but gas type not changed in the app/display (or the reverse)
- Gas conversion connector missing (NG to LP)
- Wrong conversion kit
Test and repair steps
- Warning: Do not run the unit on LP until conversion is complete and verified; exhaust odor or burning eyes can mean a bad conversion.
- Confirm the kit CK-85 = NG to LP (includes the gas conversion connector), CK-84 = LP to NG.
- Check the orifice, o-rings and emission port cap gasket were replaced.
- Plug in the LP conversion connector and set the gas type in the EZ Start Plus app (Unit Setting > Convert Gas Type) or the display.
- Check inlet gas pressure and offset pressure at the gas valve with a digital manometer, and check combustion with a gas analyzer.
- Leak test, then fill out and attach the gas conversion sticker.
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
5 models in Noritz EZ, Noritz NRCR
Other codes on the same units
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Source: Noritz EZ/NRCR Owner's Guide (Rev. 10-25), Checking for error conditions / Gas conversion, p.31, 33; Noritz NRCR Pro training (NRCR92/NRCR111, Printable V3), Field gas conversion, p.3-6. 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.