How to fix Rinnai Tankless Water Heater Code 12 [In Detail]

If you own a Rinnai Tankless Water Heater and have encountered the confusing Code 12 error, you’re in the right place. In this detailed troubleshooting guide, you will learn

  • What is Rinnai Code 12?
  • What are the reasons causing code 12 on your Rinnai water heater?
  • How to fix this code 12?

Whether you are a DIY guy or a simple house owner, Our detailed step-by-step guides will help you to get the ability to understand and solve this error from your Rinnai tankless water heater.

What is Rinnai Code 12?

Rinnai Code 12 signifies “Flame failure: either no flame detected or the flame sensor is having trouble sensing the flame in the burner“. Several factors can trigger this error, including gas supply problems, incorrect gas type, dirty burner, or issues with the flame rod wire or flame rod itself. Error code 12 is just one among several diagnostic codes used by Rinnai to pinpoint issues within your tankless water heater. This error can occur in all Rinnai models with V, RU, RL, and RUR series.

Reasons causing Error code 12 on Rinnai tankless water heater

  • No gas supply or Incorrect Gas Pressure: Inadequate gas pressure can upset your hot water unit’s operation.
  • Loose Gas Connections: Poorly secured gas connections or fittings can spell trouble.
  • Wrong Venting: Using improper venting is one of the reasons to cause Code 12.
  • Moisture (Internal Units): Internal units might suffer from moisture in the gas tubing.
  • Damaged Flame Rod Wires: Wires connected to the flame rod can be damaged or disconnected.
  • Dirty Flame Rod: Due to carbon buildup flame rods become dirty and cause issues.
  • Clogged Gas Burner: A dirty burner can disrupt combustion, causing the error.
  • Clogged Fan Blower: Dirt and debris in the fan blower can have the same effect.

While it might seem like a daunting task to pinpoint the exact cause, fear not! We’ve got a systematic troubleshooting process lined up in the next section that will simplify the task for you.

How to fix Rinnai Tankless Water Heater Code 12

No Gas Supply or Inadequate gas pressure

When your Rinnai Tankless Water Heater isn’t producing hot water and showing code 12 on the display, lack of gas supply or pressure could be one of the culprit. Follow the below steps to troubleshoot and ensure a steady flow of gas to your water heater unit:

Step 1: Check Gas Line Valves

Inspect all the gas line valves connected to your water heater. Ensure they are fully operational, in the open position, and no gas pipes should be inadvertently closed.

Step 2: Check Gas in the tank

If your system runs on natural gas or propane, make sure there is an adequate amount of gas in the tank. Running out of gas will halt your water heater’s operation.

Step 3: Maintain water heater pressure specifications

Refer to your water heater’s gas specifications, typically found on a label attached to the unit. Check for:

Inlet Gas Pressure: Verify that the gas inlet pressure matches the specifications outlined in the manual or label. The water heater requires the correct pressure to operate efficiently. For natural gas units the gas supply pressure should be between 3.5 to 10.5 inches WC (water column) and for propane units the inlet gas pressure should be in 8 to 13.5 inches WC.

Gas pressure is measured using manometers, or you can fix a pressure guage on the gas pipe to monitor the gas pressure regularly.

Step 4: Address Undersized Gas Systems

rinnai tanklesss water heater pipe sizing table with formula

Undersized gas systems can cause pressure drops beyond acceptable limits, impacting your water heater’s performance. If everything is sized correctly, you should observe no more than a slight 0.3-inch pressure drop for natural gas when all the gas water heaters in the building are operating at their highest capacity. However, if you’re using propane, a slightly higher pressure drop of 0.5 inches of water column is considered acceptable. To address this:

  • Minimum Requirements: Ensure your gas system meets the minimum requirements for your specific Rinnai model. This includes regulator size and pipe diameter.
  • Upgrade Regulator: If your regulator is too small, consider upgrading to one that can handle the gas flow required by your water heater.
  • Adjust Pipe Diameter: If your gas pipes are too narrow, consult a professional to resize them as per the specifications of your Rinnai model.

Loose Gas connections or Improper venting (Recirculation of Exhaust Gas)

When your Rinnai Tankless Water Heater displays Error Code 12, it’s due to problems with loose gas connections or improper venting. Here’s how to tackle these issues and clear the error:

Step 1: Understand the Issue

  • Loose Joints: Any loose joints or fittings in the gas connection can disrupt combustion.
  • Improper Venting: Incorrect vent terminal clearances and materials can lead to combustion gas recirculation.

Step 2: Verify Venting Components

  1. Check Instructions: Check the Rinnai venting instructions to ensure the installer used the correct venting components, with correct size and ground clearance. It’s crucial to follow Rinnai’s guidelines for safe and efficient venting.
  2. Use Approved Venting Material: Ensure that the venting material used is specifically designed and approved by Rinnai. This guarantees proper venting and prevents recirculation of combustion gases.

Rinnai venting Guidelines

Step 3: Check Vent Connection

Inspect the vent connection on your water heater. Make sure the venting material is fully engaged into the top of the water heater. There should not be any gap or leak. If necessary, separate the venting connections to confirm a proper, secure connection.

Step 4: Seek Professional Assistance

rinnai approved and tested venting system providers

If you’re uncertain about any aspect of the venting system or gas connections, or if Error Code 12 persists after these checks, it’s advisable to contact a professional technician or plumber. They can conduct a thorough assessment and address any issues with the gas connections or venting.

Damaged Silicone Protective Sleeve

Inspect the ignitor silicone protective sleeve check for any cracks or signs of heat damage. This small but vital component plays a significant role in preventing potential issues.

silicon protective sleeve of rinnai tankless water heater

Here’s what you need to do:

  1. Why It Matters: A damaged sleeve can allow sparks to seek a grounding source outside the combustion chamber. This can result in the Code 12 error on your water heater.
  2. Replace if Damaged: If you discover any cracks or heat damage, don’t hesitate to replace the silicone sleeve. It’s a relatively simple and cost-effective preventive measure to ensure the safe and reliable operation of your gas water heater.

Damaged Flame rod Wire

A damaged flame rod wire can disrupt the ignition process of your Rinnai Tankless Water Heater, potentially leading to Error Code 12. Here’s how to address this problem:

Step 1: Safety Precautions

Prioritize safety. Turn off the electrical power to the water heater and close the gas supply valve to the unit. This ensures a safe working environment.

Step 2: Locate the Flame Rod

Identify the flame rod in your water heater. It’s usually a metallic rod positioned near the burner assembly.

Step 3: Examine the Wire

rinnai tankless water heater flame rod location

Carefully inspect the wire connected to the flame rod. Look for any signs of damage, such as fraying, cuts, or exposed wires.

Step 4: Repair or Replace

If you discover any damage to the wire, you have two options:

  • Repair: If the damage is minimal and you have the necessary skills, you may attempt to repair the wire by splicing or reconnecting it. Ensure that any repairs are done securely and professionally to prevent further issues.
  • Replace: If the wire is significantly damaged or you’re unsure about the repair, it’s best to replace it entirely. Contact the manufacturer or a professional technician for a replacement flame rod wire.

Step 5: Test for Normal Operation

After addressing the damaged flame rod wire, test your Rinnai Tankless Water Heater for normal operation. Reset the Rinnai tankless water heater and observe it to ensure that it ignites without any issues. Open a hot water faucet to confirm that hot water flows correctly.

Damaged or Dirty Flame Rod

A flame rod, also known as an ignition electrode or flame sensor. Its primary function is to monitor and detect the presence of a flame in the combustion chamber. A damaged or dirty flame rod can cause issues in detecting the flame in your Rinnai Tankless Water Heater, thinking the flame is absent it shows Error Code 12. Follow the below steps to clean or replace the flame rod:

Step 1: Safety First

Always prioritize safety. Turn off the electrical power to the water heater and close the gas supply valve to the unit before performing any maintenance.

Step 2: Locate the Flame Rod

Identify the flame rod in your water heater. It’s typically a metallic rod positioned near the burner assembly.

Step 3: Examine for Damage

Carefully inspect the flame rod for any visible damage, such as bending or breakage. If you find damage, it’s essential to address it promptly.

Step 4: Clean or Replace the Flame Rod

difference between new and dirty flame rods of rinnai water heater

If the flame rod appears dirty or covered in soot or residue, cleaning may resolve the issue. Here’s how to clean it:

  1. Turn Off Gas and Power: Ensure the gas supply and power to the water heater are turned off.
  2. Remove the Flame Rod: Gently remove the flame rod from its housing. To provide good sealing flame rod is fitted with fabric gaskets so be cautious not to damage the gaskets and rod.
  3. Clean with Fine Sandpaper: Use fine-grit sandpaper to gently clean the flame rod’s surface. Remove any soot, carbon deposits, or residue. Be careful not to scratch the rod excessively.
  4. Reinstall the Flame Rod: Place the cleaned flame rod back into its housing securely.

Testing a Flame Rod on Your Rinnai Tankless Water Heater

After cleaning the flame rod if you still suspect an issue with flame rod, you can perform some live tests to diagnose the problem. Here’s how to test the flame rod:

  1. Turn on the water heater: With the water heater running, turn it on and let it reach its operational state.
  2. Position Probes: Carefully place one probe of the multimeter on the flame rod and the other probe on a ground or metal part of the unit. Ensure both probes have good contact.
  3. Measure Voltage and Current: Depending on the multimeter mode, you should get a reading:
    • In Volts Mode, you should typically get a reading between 5 and 150 volts.
    • In Amps Mode, the multimeter should display a current reading, which should be within an expected range.
  4. Normal Reading: If the multimeter shows readings within the expected range, it suggests that the flame rod is functioning correctly.
  5. No Reading or Abnormal Reading: If you get no reading or readings outside the expected range, it may indicate a problem with the flame rod, its connection, or related components.

If the flame rod is broken or completely corroded, you need to replace it with the new one. Just remove the old flame rod and replace the new one in its place and connect the wires, that’ it. Reset the heater the test for its working.

Clean the Dirty Components

Maintaining a clean and debris-free system is essential to ensure the optimal performance and safety of your Rinnai Tankless Water Heater. Here’s how to deal with dirty components:

Inspect and Clean

  1. Combustion Chamber: Inspect the combustion chamber for any debris or dirt buildup. Ensure it’s free from any foreign materials that could interfere with the combustion process.
  2. Fan Blower: Check the fan blower for dirt and dust accumulation. If present, carefully clean it using a soft brush or compressed air.
  3. Intake and Exhaust: Examine the intake and exhaust vents for any obstructions, such as leaves, insects, or debris. Clear any blockages to ensure proper air circulation.
  4. Venting System: A clean venting system is crucial. Some homeowners find it effective to use a shop vaccum cleaners to remove debris from the venting system. Ensure that the venting pipes are free from any blockages that could impede the safe removal of exhaust gases.

Thank you for taking the time to read our Troubleshooting guide on Rinnai code 12. We hope it has been informative and helpful in resolving the issue. If you have any doubts or lingering questions, please don’t hesitate to ask in the comments below. We value your feedback and are here to assist you.

We look forward to having you visit us again for more insights and solutions in the future. Your satisfaction is our priority, and we’re here to ensure your home systems run smoothly.

Joseph Miller

Joseph Miller is a highly experienced water heater repair expert with a passion for keeping homes warm and comfortable. With over 50 years of industry expertise, Joseph has developed a deep understanding of water heater systems and the intricacies of their repair and maintenance.

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