HVACopediaRinnai · Tankless water heater
nG Initial setting: natural gas
What the display is showing
Shown on the controller of RX/CX units during first-time setup. It means natural gas is chosen as the gas type. When setup is finished, the controller alternates nG with In or Out while the Priority button blinks, showing the saved gas and location settings.
Applies to: Rinnai SENSEI RX/CX tankless (RX, RXP, CX, CXP)
What to do
- At first power-up SEt shows and the Priority LED blinks. Press Priority: nG appears.
- Press On/Off to confirm natural gas. For propane, press Up or Down to change to LPG, then On/Off.
- To redo, press Up to go back to the first step; to accept, press Priority.
- The gas type can also be changed later with parameter 10, but only within 20 minutes after power is supplied.
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
- Priority light Priority light on (this controller is in charge)
- SE Cascade diagnostic display (error on secondary unit)
- SEt Initial settings not yet confirmed
- SS Service Soon alert (also listed as 55)
- dES Descaling (flush) mode
- rnS Descaling finished, rinse now
- t Venturi reset sequence: step t
- °C/°F Temperature scale switch (Celsius / Fahrenheit)
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Source: Rinnai SENSEI RX Residential Installation and Operation Manual (100000839), 4.12 Initial Settings p.46-47. Summarized in our own words; check the original manual for your model.
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.