HVACopediaRinnai · Tankless water heater
11 (VA, VB, VC, KA, RH-180, KCM alternate checks) Code 11 - alternate checks for VA, VB, VC, KA, RH-180 and KCM
What the control is telling you
Second set of Code 11 checks shown on page 16. The steps are for the listed models. Turn off electrical, gas and water before the steps that require it.
Applies to: VA, VB, VC, KA, RH-180 and KCM water heaters
Likely causes
- Gas valves not open or air not purged
- Inlet gas pressure too low at high fire
- Gas type DIP switch set wrong
- Igniter or ignition wiring problem
- Loose or floating flame rod or electrode
- Wrong flame rod wire at the flame rod
- Carbon or white deposit on the flame rod
- Blocked burner orifices or heat exchanger fins
Test and repair steps
- Verify all gas valves on the gas system are open and feeding the correct pressure.
- Verify all air was purged from the gas lines after installation.
- Verify inlet gas pressure at the rating plate at high fire. On condensing units, install the front panel before testing inlet pressure.
- Verify gas type matches the water heater.
- Verify the gas type DIP switch on the PC board is set to the correct gas type.
- Check the igniter as described on the Code 11 steps. Spark must be seen when cycling.
- Check that the ceramic sparker electrode is tight. Replace the gasket and reinstall if loose.
- Verify the proper flame rod wire is connected to the matching flame rod. The stamped letter on the bracket is Y for yellow, R for red and B for blue.
- Verify the flame rod is tight. A loose flame rod can cause Code 11.
- Watch the view window during ignition. If flame is seen, check the flame rectification circuit.
- Remove the igniter and flame rod, inspect for carbon or white build-up, and clean both. Use a new gasket if the seal is broken.
- Remove the burner manifold, clear orifices and burner and air chambers, and clean heat exchanger fins with 120 PSI compressed air. Replace the heat exchanger if needed.
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
- RUCS/RUS unit clearances · Non-SENSEI
- RUCS/RUS water quality limits · Non-SENSEI
- Water quality limits - RU/RUR/CU · SENSEI
- Clearances - RU/RUR/CU · SENSEI
Models that show this code
78 models in SENSEI, Non-SENSEI
Other codes on the same units
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Source: Troubleshooting Tankless Water Heater Diagnostic Codes, p. 16. Summarized in our own words; check the original manual for your model.
Homeowner looking at this code? See what it means for you and when to call a technician.
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.