HVACopediaRinnai · Tankless water heater
t Venturi reset sequence: step t
What the display is showing
One of the screens shown on the controller while stepping through the reset procedure after cleaning the venturi (code 17) or replacing the gas valve/venturi assembly (code 52). Each press of button B on the PC board for 1 second moves to the next screen; the manual does not give the letters a separate meaning.
Applies to: Rinnai SENSEI and SENSEI RX/CX tankless
What to do
- With the controller blank, press B for 1 second at a time to advance: SENSEI shows t, F, S, E; RX/CX shows dES, t, AdJ, F, A, E.
- E appears only while code 17 or 52 is active.
- Finish by pressing A and B together for 10 seconds until ECL shows.
Settings for these units
RSC supply connection sizes · SENSEI
| Connection | Size |
|---|---|
| Gas | 3/4 in. NPT |
| Cold inlet | 3/4 in. NPT |
| Hot outlet | 3/4 in. NPT |
| Condensate drain | 1/2 in. NPT |
| Pressure relief valve | M33 thread |
The PRV and its adapter come in the box; PRV must be rated 150 psi and at least the heater Btu/h.
Condensate drain line must stay at least 1/2 in. over its whole length.
RSC water quality limits · SENSEI
| 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 |
Damage from water above these limits is not covered by warranty.
Hard water should be treated; use the Service Soon (SS) reminder (parameter 03) for flushing intervals.
- RSC clearances to combustibles · SENSEI
- RSC temperature settings available · SENSEI
- RX supply connection sizes · SENSEI RX/CX
- RX water quality limits · SENSEI RX/CX
- RX water treatment and flushing by hardness · SENSEI RX/CX
- RX clearances to combustibles · SENSEI RX/CX
Models that show this code
30 models in SENSEI RX/CX, SENSEI
Other codes on the same units
- S Venturi reset sequence: step S (SENSEI)
- 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
- nG Initial setting: natural gas
- rnS Descaling finished, rinse now
- °C/°F Temperature scale switch (Celsius / Fahrenheit)
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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.