HVACopediaRinnai · Tankless water heater
SEt Initial settings not yet confirmed
What the control is telling you
Shown on first power-up of a SENSEI RX/CX unit, which ships configured for natural gas and indoor installation. The installer must confirm or change the initial settings before the heater is used.
Applies to: SENSEI RX/CX series only
Likely causes
- Unit powered up for the first time
- Factory default settings (natural gas, indoor) not yet confirmed by the installer
- Initial settings need to be changed to match the actual installation
Test and repair steps
- Warning: Using the heater before the correct initial settings are selected creates a hazard that can cause injury or property damage. Only a trained, qualified professional should do the initial setup.
- Option 1 (recommended) confirm or change the initial settings from a smart device over Bluetooth Low Energy (BLE).
- Option 2 confirm or change the initial settings using the water heater's controller.
- See the "Initial Settings" section of installation manual 100000839 or 100000840 for full details.
Settings for these units
RX supply connection sizes · SENSEI RX/CX
| Connection | Size |
|---|---|
| Gas | 3/4 in. MNPT |
| Cold inlet | 3/4 in. MNPT |
| Hot outlet | 3/4 in. MNPT |
| Condensate drain | 1/2 in. MNPT |
Vent connection: 2 in. nominal PVC/CPVC/PP or 3 in./5 in. concentric.
Full specs (input, flow, weight) are only on each model's spec sheet, not in this manual.
RX water quality limits · SENSEI RX/CX
| Contaminant | Maximum level |
|---|---|
| Total hardness | Up to 200 mg/L |
| Aluminum | Up to 0.2 mg/L |
| Chlorides | Up to 250 mg/L |
| Copper | Up to 1.0 mg/L |
| Dissolved CO2 | Up to 15.0 mg/L |
| Iron | Up to 0.3 mg/L |
| Manganese | Up to 0.05 mg/L |
| pH | 6.5 to 8.5 |
| TDS | Up to 500 mg/L |
| Zinc | Up to 5 mg/L |
Water damage beyond these limits is not covered by warranty.
- RX water treatment and flushing by hardness · SENSEI RX/CX
- RX clearances to combustibles · SENSEI RX/CX
- RX temperature settings available · SENSEI RX/CX
Models that show this code
10 models in SENSEI RX/CX
Other codes on the same units
- 66 Bypass flow servo fault
- 70 PC board fault
- 71 Gas solenoid valve fault (SV0–SV4 on Non-SENSEI)
- 72 Flame rod fault
- FF Maintenance performed (history marker)
- LC Scale build-up in heat exchanger (LC, LC0–LC9, 00)
- SE Cascade diagnostic display (error on secondary unit)
- SS Service Soon alert (also listed as 55)
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Source: Rinnai Troubleshooting TWH Diagnostic Codes (100000652), p.5. 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.