Rinnai Error Code 11 — What It Means
Rinnai Error Code 11 on a tankless water heater means no ignition — the unit attempted to light the burner but could not detect a flame within the trial-for-ignition period. The unit tried to ignite (you may have heard clicking), but the flame sensor (ionization rod) did not detect a flame, and the unit locked out. Error 11 is one of the most common Rinnai service codes and in many cases is caused by a simple gas supply issue rather than a failed component.
Common Causes
- No gas or inadequate gas supply — A closed gas shutoff valve, a recently run-out propane tank (LP units), or insufficient gas pressure prevents ignition entirely.
- Air in the gas line — After work on the gas supply or extended shutdown, air trapped in the gas line prevents combustion on the first several ignition attempts.
- Dirty igniter or flame sensor — Carbon buildup on the ignition electrode or ionization rod prevents the spark from jumping or the flame from being detected.
- Low gas pressure — Supply pressure below the required minimum (typically 4” WC for natural gas, 8” WC for LP) results in a flame too weak to register on the sensor.
Step-by-Step Fix
- Confirm gas supply is on — Check that the gas shutoff valve at the unit is fully open. For propane units, check the LP tank level. Check that no other gas appliances have lost service (indicating a supply issue).
- Bleed air from the gas line — If this is a new installation or the line was recently worked on, open a downstream gas appliance briefly to purge air from the line. Then attempt to fire the Rinnai again.
- Clean the ignition electrode and flame rod — Shut off power (and gas at the unit) and remove the combustion chamber access panel. Lightly clean the ignition electrode tip with fine steel wool, and clean the ionization rod with emery cloth.
- Check gas pressure — Low pressure requires a manometer test at the gas valve inlet. This is a gas technician task if you don’t have the equipment.
- Reset the unit — Press the ON/OFF button to reset Error 11 after addressing the root cause. Allow 30 seconds for the unit to re-initialize before calling for hot water. If Error 11 returns on the first try, repeat the gas supply check.
Parts Often Needed
| Part | Notes |
|---|---|
| Ignition electrode | Replace if electrode tip is worn, cracked, or gap is incorrect |
| Flame sensor (ionization rod) | Replace if cleaning doesn’t restore detection |
| Gas valve | Replace only after confirming gas supply pressure is correct and ignition components are functional |
Need Replacement Parts?
Finding the right replacement parts for your equipment is critical to getting it running again. Check current prices on Amazon — prices and availability change frequently.
When to Call a Pro
If gas is confirmed at the unit, the electrode and flame sensor are clean, and Error 11 persists, the gas valve may not be opening fully or gas supply pressure may be insufficient. Both require a licensed gas technician with a manometer and the Rinnai service manual’s pressure specifications.