HVACopediaRinnai · Tankless water heater
A Venturi reset sequence: step A (RX/CX)
What the display is showing
A screen shown on SENSEI RX/CX units while stepping through the venturi/gas valve reset procedure by pressing button B on the PC board for 1 second at a time. It comes after F and before E.
Applies to: Rinnai SENSEI RX/CX tankless (RX, RXP, CX, CXP)
What to do
- Press B for 1 second from the F screen to reach A, then press B again for E.
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
- 72 Flame rod fault
- 888 Initial settings saved
- AdJ Venturi reset sequence: step AdJ (RX/CX)
- Bluetooth LED blinking Bluetooth LED blinking (push-button pairing mode)
- Bluetooth LED solid Bluetooth LED solid blue (app pairing mode)
- Diag history Maintenance code history viewer (last 9 codes)
- Diagnostic history Show last 9 maintenance codes
- E Venturi reset sequence: step E (code 17 or 52 only)
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Source: Rinnai Troubleshooting TWH Diagnostic Codes (100000652), Code 17 and Code 52 reset procedure p.28-29. 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.