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Rinnai Tankless Water Heater Common Error Codes & Solutions

1. Code Issue: LC (or 00 on some models) - Limescale/Scale Build-up Detected

• Cause: This is one of the most common issues, especially in areas with hard water (like Denver!). Minerals (calcium and magnesium) in the water accumulate on the heat exchanger over time, reducing efficiency and eventually blocking flow.

• How to Fix:

  1. Perform a professional descaling/flushing: This is the primary solution. You'll need a descaling kit (which includes a pump, hoses, and a descaling solution, typically white vinegar or a commercial descaler).

     • DIY (for experienced users): Shut off power and water to the unit. Connect the pump and hoses to the isolation valves (hot and cold service ports). Circulate the descaling solution through the unit for 45-90 minutes. Flush thoroughly with clean water.

     • Professional Recommendation: While DIY is possible, it's often best to have a professional plumber perform this annually. They have the right equipment and expertise to ensure a thorough and safe flush.

  2. Consider a Water Softener: If you frequently get LC codes, a whole-house water softener is a long-term solution to prevent future scale buildup.

2. Code Issue: 10 - Air Supply or Exhaust Blockage (Combustion Failure)

• Cause: The unit isn't getting enough fresh air for combustion or its exhaust is blocked. This can be due to:

  • Obstructions in the vent pipes (e.g., bird's nest, debris).

  • Incorrect vent pipe installation (too long, too many bends, wrong material).

  • Blocked air intake screen.

  • Malfunctioning combustion fan.

• How to Fix:

  1. Inspect Venting: Visually check the exhaust and air intake pipes (usually on the exterior of your home/business) for any visible blockages. Clear any debris.

  2. Check Clearances: Ensure there's nothing obstructing the air flow around the unit itself.

  3. Verify Venting Installation: If this is a new installation or you suspect improper venting, this is a job for a professional. Incorrect venting can be very dangerous.

  4. Reset Unit: Try turning the power off to the unit for 30 seconds to a minute, then turn it back on to reset.

  5. Professional Service: If the issue persists after clearing obvious blockages, or if you suspect a fan malfunction, call a technician.

3. Code Issue: 11 - No Ignition / No Gas Supply

• Cause: The water heater attempted to ignite but couldn't detect a flame. This typically points to a gas supply issue or a problem with the ignition system.

• How to Fix:

  1. Check Gas Supply:

     • Ensure the gas valve to the water heater is fully open.

     • Check if other gas appliances in your home (furnace, stove) are working to rule out a general gas supply problem to the property.

     • Confirm your gas meter valve is open.

  2. Bleed Air from Gas Lines: If it's a new installation or gas lines were recently worked on, there might be air in the lines. This usually purges itself, but if not, it may need professional assistance.

  3. Reset Unit: Power cycle the unit (turn off power, wait, turn on).

  4. Professional Service: If gas supply is confirmed, the issue could be a faulty igniter, flame sensor, gas valve, or control board. These require a qualified technician.

4. Code Issue: 14 - Thermal Fuse / Overheating

• Cause: A safety device (thermal fuse) has tripped due to the unit overheating. This can be caused by:

  • Severe scale buildup (leading to inefficient heat transfer).

  • Restricted water flow through the unit.

  • Blocked exhaust/air intake (similar to Code 10).

  • A faulty thermal fuse itself.

• How to Fix:

  1. Check Water Flow: Ensure all hot water faucets are fully open and there are no closed isolation valves or severely restricted lines leading to the unit.

  2. Check for Scale (LC Code): If you've been getting LC codes, a flush is likely overdue.

  3. Inspect Venting: Double-check for any blockages as with Code 10.

  4. Reset Unit: Power cycle.

  5. Professional Service: If overheating continues, or if the thermal fuse is faulty, it needs professional diagnosis and replacement.

5. Code Issue: 61 - Combustion Fan Failure

• Cause: The unit's combustion fan (which draws in air and expels exhaust gases) is not operating correctly.

• How to Fix:

  1. Check for Obstructions: Ensure nothing is physically impeding the fan's blades or its ability to spin.

  2. Check Wiring: Look for loose or disconnected wires around the fan motor. (Only if comfortable and power is off!)

  3. Reset Unit: Power cycle.

  4. Professional Service: This usually indicates a faulty fan motor or control board, requiring replacement by a qualified technician.

General Troubleshooting Tips for Rinnai Tankless:

• Power Cycle: For many codes, turning the power off to the unit at the breaker for 30-60 seconds and then turning it back on can sometimes clear a temporary glitch.

• Check Water Flow Rate: Ensure you have adequate water flow. If the flow rate is too low, the unit may not fire up.

• Clean Inlet Filter: Your unit has a small screen filter on the cold water inlet. Turn off water and power, then remove and clean this filter.

• Read Your Manual: Your specific Rinnai model might have unique codes or slightly different troubleshooting steps.

• Professional Help: For anything involving gas lines, electrical components, or if the issue persists after basic troubleshooting, always call a qualified plumber or Rinnai-certified technician. They have the diagnostic tools and expertise to safely and effectively resolve complex issues.