Rinnai error codes are ways Rinnai products communicate problems with the system. Rinnai code 12 indicates several issues within the Rinnai water heater and that there is a lack of flame or flame failure within the system. Flame failure may indicate the lack of gas supply, not using the proper gas type, cleaning, broken elements within the heater, and more.

Error code 12 is found on most models, like the RU, RL, V, and RUR series of water heaters. An error code 12 means there is no flame or flame failure within the system and that the tank is not registering a flame in the combustion chamber.
You can view this error code from the control panel where you set the temperature. If the system doesn’t have a control panel, you can find the error on the remote controller.
How do I fix my Rinnai Code 12?
While it could be a flame error code, a flame rod may not be the actual source. Your system may generate this code for many reasons.
No Supply of Gas
Inspect all gas line valves on the water heater to make sure they are operational and that the gas pipes are not closed. If the system uses propane, make sure there is an adequate amount of gas in the tank.
The water heater needs the proper amount of gas to function. If you are unsure of what that is, check the specifications of your water heater. These are usually on a label attached to the heater. Check to see you have the proper inlet pressure and if the system is meeting the minimum amount necessary.
Improper sizing causes the gas system to become undersized (insufficient regulator and smaller diameter), leading to an increased pressure drop than what is in the specifications.
Not the Proper Gas Type
A Rinnai tankless water heater uses propane or natural gas to run. Ensure that you use the right fuel type according to the manufacturer’s specifications for your hot water system.
Interruption of Gas/Power Failure
A power failure causes an interruption in the gas supply necessary for the tank to function properly. In the event of a power outage, the system shuts down. Once power is restored, it doesn’t power up like most appliances. You will get a Rinnai error code until you deal with the problem.
If, however, the gas line contains air, you will need to have it emptied. Only a professional can bleed the air from the gas pipes.
Broken or Disconnected Flame Rod
Examine the flame rod to see if it has become disconnected. If there is a crack/damage in the ceramic sleeve, replace it.
The ignitor and the flame rod are attached to the mounting bracket. They shouldn’t be misplaced or come loose. Some Rinnai systems will have two, while others have one flame rod.
Wires should not be damaged, frayed, or broken. They should be attached to the electronic board and the flame rod. The rod itself needs to come into contact with the flame to ignite to heat the water. The flame should be clear and blue with a stable pattern.
If the igniter or rod has a carbon build-up, use fine sandpaper and cloth to clean it. Scotch Brite pads word as well.
Recirculation of Exhaust Gas
An expert should perform unit installation and venting. They must follow the specifications, code, and instructions for proper installation. Error code 12 may appear if the venting contains components not approved by the company, loose connections, or is the right venting size, have the proper clearance, or is the wrong material.
If exhaust gases come from the back of the system instead of venting out, improper gas combustion can occur when you see a reddish-yellow burner flame with an unstable pattern.
Components Need Cleaning
Venting systems, combustion chambers, intake exhaust, and fan blower all need to be kept clean. Cleanliness matters because it ensures the gas can burn clean and exhaust gasses are safely vented to the outside of the house.
Rinnai tankless water heaters have several delicate and advanced components sensitive to build-up, contamination, and condensation. Homeowners often use a shop-vac to remove the garbage from venting systems.
Electrical Wiring Issues
To work efficiently, tankless water heaters require proper grounding. Cables should be connected tightly, without damage, and be dry. Examine components for electrical shorts regularly.
Major Damage to Components
Sometimes the components can wear out or be faulty. Replace the electronic board and gas valves in this case. Also, before anyone services, the water heater, electrical supply, water, and gas should all be turned off.

Where are Rinnai Error Codes?
The Rinnai error codes are =located on the control panel. Sometimes, depending on the model, they can be found on the remote control.
How do I Reset my Rinnai?
Resetting your Rinnai is done by pushing the two switches labeled A and B on the electrical board simultaneously for five seconds. The water heater then returns to normal, and the error zeros out. This is a hard reset.
You cannot ignore any error code on a Rinnai Tankless Water heater system. It will not run until you deal with it. For this reason, homeowners should familiarize themselves with what the errors mean and how to troubleshoot them.
While the system is durable and has longevity in mind, sometimes things can happen. The best thing for an owner to do is to be prepared. This way, if you face any issues, you will know how to navigate them.
Error code 12 can exist and not be related to problems with the flame rod. Many other components of a Rinnai heater can be the source of this error code. These troubleshooting tips should help you in case this message returns and are helpful with solving the issue. For some steps, however, you will need a qualified technician.