Most Common Rinnai Tankless Water Heater Error Codes: How to Fix Them

You can rely on your Rinnai tankless water heater for a steady supply of hot water. But sometimes, it may flash an error code throughout its lifespan. Do not panic; error codes can pop up, and they’re all fixable.

For over 15 years, we at Monkey Wrench Plumbing, Heating, Air & Electric have serviced hundreds of tankless water heaters throughout the Los Angeles area, including units from Rinnai. Years of working with Rinnai have given us better insight into how their tankless water heaters operate and what can cause error codes to appear.

This article will review the most common Rinnai error codes and how a technician will need to help you fix these error codes.

• Rinnai error code 10
• Rinnai error code 11
• Rinnai error code 12
• Rinnai error code LC
• Rinnai error code 14

Before proceeding, it’s important to note that unplugging and plugging your Rinnai tankless water heater will not clear the error code and properly address what’s causing it.
Now, let’s get started!

Most Common Rinnai Tankless Water Heater Error Codes

There are over a dozen different error codes that can appear on your Rinnai tankless water heaters.
A complete list of Rinnai’s error codes can be found online. A physical copy of the tech sheet is also on the interior side of the tankless water heater cover panel. If you see an error code appear, contact a technician immediately.
One of the first codes we’ll cover is Rinnai error code 10.

Rinnai Error Code 10

If your Rinnai tankless water heater flashes error code 10, it means there’s a blockage in the air supply or exhaust. This code can appear for several reasons, and technicians will have to check that nothing is blocking the exhaust or flue inlet. Rinnai error code 10 can appear on any of the brand’s condensing and non-condensing tankless water heaters.
Once the inspection is complete, the technician will move forward with the required repairs.

How to Fix Rinnai Error Code 10

The technician will remove anything obstructing the air supply or exhaust. They will also inspect the ventilation system of the Rinnai tankless water heaters to ensure the appropriate materials are being used and the vent length meets the manufacturer’s standards. The technician should address any issues with the vents as well.
Other inspections include checking the unit’s condensation collar and dip switches and making sure nothing is blocking the fan. After the issues are resolved, the technician will plug the tankless unit back in and run a cycle to ensure it’s providing hot water.

Rinnai Error Code 11

Another commonly seen code is Rinnai error code 11, which indicates there is no ignition detected. An ignition failure will result in a lack of hot water with your tankless water heater.
A lack of gas supply to the Rinnai tankless water heater can trigger error code 11. Issues with the unit’s ignition system may also cause the error code to flash on the control panel.
Again, the best course of action is to contact a technician for further assistance on Rinnai error code 11.

How to Fix Rinnai Error Code 11

Rinnai error code 11 has different repairs available since there are several reasons the code can appear. A technician will first confirm that the unit is receiving gas from the supply line. If it is, they will shut off access, unplug the tankless water heater, and continue their inspection.
They will also need to disassemble the tankless water heater from the inside to check for problems with the igniter, flame rod, or other parts of the ignition system. Any damaged or defective parts will have to be replaced or repaired. The technician may help submit the repair for a warranty claim if it might qualify.
Besides a bad ignition system, flame failure is another issue that can trigger an error code with your tankless water heater.

Rinnai Error Code 12

Rinnai error code 12 indicates a flame failure with the tankless water heater that is preventing it from heating water. Your tankless water heater may get this error for several reasons.

• Faulty or damaged flame rod, igniter, or other ignition parts
• Bad gas valves
• Lack of gas supply
• Loose or faulty connections of parts near the flame rod
• Obstructed ventilation

Like error code 11, this Rinnai error code has various possible causes but should only be investigated by a qualified technician. Most of the parts that can trigger Rinnai error code 12 are located within the unit and need to be disassembled by the technician.

How to Fix Rinnai Error Code 12

After disconnecting the tankless water heater, the technician will confirm whether the unit is receiving gas from the supply line and then inspect the parts that produce a flame. Some of the common repairs for Rinnai error code 12 include,

• Ensuring the gas line to the unit is sized properly
• Confirming that the vent length meets specifications
• Check any loose wiring connections
• Replace the flame rod or any component that’s part of the ignition system
• Replace the burner plate or clean it if it has debris

Sometimes, the technician may repair the issue the same day if they have all the required parts in stock in their work vans. Sometimes, a technician may have to pick up a part or order it to arrive so they can complete the repair.

Rinnai Error Code LC

Rinnai error code LC means there is scale buildup in the heat exchanger. It is one of the most common error codes affecting Rinnai tankless water heaters in areas with hard water, like Los Angeles and the surrounding areas. Limescale is a byproduct of hard water that forms when it comes in contact with hot water.
The heat exchanger transfers heat to cold water, and scale is much more likely to form there, triggering Rinnai error code LC. The error code alerts you that a significant amount of scale is present and must be addressed.
Ignoring the error code can lead to a loss in heating efficiency and cause irreversible damage to the heat exchanger. Luckily, Rinnai error code LC can be easily addressed and is one of the few error codes where you may be able to clear yourself.

How to Fix Rinnai Error Code LC

A tankless water heater flush can help clear Rinnai error code LC. You can flush your Rinnai tankless water heater with a few supplies in four easy steps.
You can also contact a technician to perform a tankless water heater flush, which is usually part of routine maintenance for tankless units. A technician can also disassemble the Rinnai tankless water heater and see the impact of the scale on the heat exchanger. In some cases, if the unit hasn’t been properly maintained or flushed, the heat exchanger may need to be replaced.
Water filtration can stop scale from forming on heat exchangers. Installing a water softener can eliminate scale and prevent Rinnai error code LC from appearing.

Rinnai Error Code 14

Rinnai error code 14 means there is an issue with the tankless water heater thermal fuse or the overheat sensor. If a Rinnai tankless water heater is overheating water beyond the set temperature, it will trigger error code 14 as a safety alert. It’s common for the tankless water heater to shut down as a safety precaution, with only cold water available.

• Scale buildup on the heat exchanger
• Broken or faulty thermal fuse or sensors
• Poor combustion

The unit will not produce any hot water until the code is cleared. Contacting a technician to diagnose the problem is the first step in removing Rinnai error code 14.

The unit will not produce any hot water until the code is cleared. Contacting a technician to diagnose the problem is the first step in removing Rinnai error code 14.

How to Fix Rinnai Error Code 14

A technician can apply a fix after diagnosing Rinnai error code 14. Some of the common fixes include.

• Descaling and flushing the tankless water heater, similar to Rinnai error code LC
• Inspect the burner assembly, igniter, flame sensors, thermal fuse, and connections, and replace if necessary
• Check gas pressure
• Clear obstruction in the venting that is affecting the combustion
• Once a fix is applied, the technician will test your Rinnai tankless water heater to ensure it’s functioning correctly and providing the right hot water temperature.

Brushed Up on Rinnai Error Codes

Error codes may seem unavoidable, but they’re often all fixable. Now that you know the most common Rinnai error codes, you can feel more assured that your specific error code can be inspected and repaired.
At Monkey Wrench Plumbing, Heating, Air & Electric, we have cleared thousands of error codes that are common in tankless water heaters. We work with all of the top brands, like Rinnai, to ensure that we utilize all our resources and proper tools to fix any error code that can appear on your Rinnai tankless water heater.
If you’re dealing with an error code, contact us using one of the buttons below to schedule an appointment with one of our technicians. You can also directly book an appointment through our online tankless water heater repair scheduler.
Repair costs can vary from error code to error code. To better understand what tankless water heater repair prices look like, learn more about how much it costs to fix your tankless water heater repair.