HVACopediaRinnai · Tankless water heater
17 Venturi blockage
What the control is telling you
The unit has detected a blocked venturi or restricted air path; after cleaning, a manual reset sequence on the PC board is needed to return to normal operation.
Applies to: SENSEI Series; SENSEI RX/CX Series
Likely causes
- Condensate drain line not draining
- Obstruction in intake, exhaust chamber or vent termination
- Debris build-up in the venturi assembly
Test and repair steps
- Confirm the condensate drain line drains properly.
- Inspect the full vent system (intake, exhaust chamber, termination) for obstructions.
- Remove the gas valve and venturi assembly from the fan motor and inspect the venturi for debris.
- Clean the venturi assembly, reinstall it, then perform the code 17 reset on the PC board.
- SENSEI reset With controller off, press button B for 1 s repeatedly through t, F, S, E (E shows only with code 17/52 active), then hold A and B for 10 s until ECL appears.
- SENSEI RX/CX reset With controller off, press button B for 1 s repeatedly through dES, t, AdJ, F, A, E (E shows only with code 17/52 active), then hold A and B for 10 s until ECL appears.
- Once ECL is displayed the reset is complete and the water heater should resume normal operation.
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
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Source: Rinnai Troubleshooting TWH Diagnostic Codes (100000652), p.28–29. Summarized in our own words; check the original manual for your model.
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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.