A Rinnai error code 11 signifies an ignition failure—which means your tankless water heater is unable to spark or detect a flame. This prevents the unit from heating water and is displayed when the ignition sequence fails.
🔍 Common Causes and Step-by-Step Fixes
1. Gas Supply Issues
The gas valve may be fully or partially closed, or the gas type/pressure may be incorrect or inconsistent.
Ensure the valve is fully open, gas matches your unit’s specification, and inlet gas pressures meet the manufacturer’s guidelines (e.g., 5″–10.5″ W.C. for natural gas, 8″–13.5″ W.C. for propane).
Purge the gas line to remove trapped air after installation.
2. Igniter Malfunction
The igniter might not generate a spark due to dirt, misalignment, broken wiring, or wear.
Inspect wiring, clean the igniter if dirty, and ensure it’s mounted correctly with a proper gasket. Replace if it’s damaged or fails to spark.
3. Faulty Flame Rod (Sensor)
The flame rod may be loose, dirty, cracked, or improperly wired
Clean it gently, ensure it’s tightly mounted, and replace the gasket after maintenance. Replace the rod entirely if corrosion or damage is visible
4. Venting or Airflow Problems
Blocked or improperly installed intake/exhaust vents can disrupt combustion.
Inspect both intake and exhaust venting, confirming clearance and clearing any obstructions to maintain proper airflow.
5. Control Board or Wiring Issues
Damaged wiring or defects on the PC/control board may disrupt ignition pressure or signal.
Visually inspect components for damage or loose connections. If needed, use a multimeter for voltage/resistance checks (see Rinnai spec ranges). Replace the board if it’s faulty.
6. Additional Diagnostics
Power off and reset the unit (via control panel or breaker), then restart to clear errors—as this may resolve temporary glitches.
If the unit has firmware support, updating it can sometimes address underlying control logic issues.
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✅ Troubleshooting Checklist
| Component | What to Inspect or Do |
|---|---|
| Gas Supply | Ensure gas valve is open; check type (natural vs propane) and pressure levels |
| Igniter | Inspect wiring, alignment; clean or replace if no spark |
| Flame Rod | Confirm secure mounting, clean surface, replace if damaged |
| Venting | Clear intake/exhaust vents; confirm installation and proper airflow |
| Control Board/Wiring | Check for loose or corroded connections; verify voltage/resistance to gas valve |
| Unit Reset | Power-cycle to clear transient faults; restart to retry ignition cycle |
| Firmware (if available) | Update to latest version for any control improvements |
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⚠️ Safety and Professional Help
These tasks often involve gas lines, high voltage, and internal components—which can be dangerous if mishandled.
If you’re uncomfortable or lack experience with electrical and plumbing systems, it’s strongly recommended to call a certified Rinnai technician.
Using proper tools like a multimeter to check ignition voltage or gas pressure may be necessary.
✅ Final Summary
Error 11 = “No ignition”, typically caused by issues related to gas supply, igniter, flame rod, venting, or control circuitry.
Start with basic checks (gas and airflow), clean or reseat ignition components, and power-cycle the unit.
If the error persists, seek professional repair to safely diagnose and fix the core issue.
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