Facebook
When you shop through links on our site, we may earn an affiliate commission. This educational content is not intended to be a substitute for professional advice.

Rinnai Tankless Error Code Troubleshooting

Updated
Let us help you understand Rinnai tankless error codes and how to troubleshoot them.

Are you the proud owner of a Rinnai tankless water heater? Rinnai’s tankless heaters are among the best you can buy, but no piece of technology is flawless and problems will eventually occur, leaving you with no hot water.

To help you quickly understand issues when you encounter them, Rinnai’s boilers provide an error code. This code corresponds to a specific problem. The solution might be as simple as resetting the unit, or you might need to call a professional.

In this article, we will take a closer look at Rinnai’s error codes, where you can find them, and what you need to do when you see them. This should help you solve any issues with your boiler as quickly as possible.


Where Will I Find Rinnai Error Codes?

Rinnai’s tankless water heaters feature a self-diagnostic tool built that checks it as it operates. When something goes wrong, it shuts itself off and displays an error code.

On the MC-91, MCC-91, and MC-502 the error code will be displayed on the temperature panel. On the MC-100 and BC-100, it will flash on the clock display.

When an error code appears and your water is not heating, you can often complete a few simple steps and resolve the issue. However, these are complex pieces of technology and there might be a more delicate issue — in these cases, you should consider calling a qualified technician instead.

SAFETY FIRST

If a code appears related to flammable vapors, don’t attempt to work on your heater. You must first call a professional to ensure the area is safe.

Rinnai Tankless Error Codes

Let’s take a closer look at Rinnai error codes, what they mean, and how they can be resolved. This should significantly speed up your Rinnai tankless error code troubleshooting.

Error Code 02

What It’s Telling You

  • The freeze protection mode has prevented the water heater from working.

The Solution

  1. Contact the support team at 1-800-621-9419.

Error Code 03

What It’s Telling You

  • The power supply has been interrupted during an automatic bath fill. If this continues to happen after the power has returned, this function will be unusable.

The Solution

  1. Turn off the faucets: Turn off all the faucets in your home.
  2. Reset the appliance and the code: Find the On/Off button and press it twice.
  3. A fault with the PC board: If the code reappears, you might need to replace the PC board.

Error Code 05

What It’s Telling You

  • There is a fault on the bypass servo if the heater has bypass valves fitted.

The Solution

  1. Disconnect the power supply: Turn the power supply off and on again.
  2. Turn on the hot water: Open a hot water faucet and the heater should fire up.
  3. Replace the bypass valve: If the code reappears, the bypass valve is faulty and should be replaced.

Error Code 07

What It’s Telling You

  • The circulation flow rate through the appliance has fallen below 2.1 GPM.

The Solution

  1. Check the power supply: Make sure the heater’s power supply is active.
  2. Is the water supply on? Ensure your water supply to the unit is turned on and at a minimum of 30 psi.
  3. Check the wiring: Make sure there are no damaged or loose wires in the pump harness.
  4. Check the water filter: Look for any blockages and clear them.
  5. Flush the heat exchanger: Follow your owner’s manual to flush any build-up from the heat exchanger.

Error Code 10

What It’s Telling You

  • Exhaust or air supply blockage.

The Solution

  1. Check the vents: Make sure that only the manufacturer’s venting materials are being used, there are no obstructions, and the clearances and limits are correct.
  2. Improper installation: It is possible that the vent pipe has not been installed correctly.

Error Code 11

What It’s Telling You

  • There is a fault with the ignition.

The Solution

Assuming that the gas type and pressure are correct, it is on, and there is no air in the system, check the following:

  1. Check the igniter: Make sure a spark is being generated.
  2. Examine the wiring: Check that the connections of the wiring are correct.
  3. Is the unit grounded? Double-check that the heater is grounded properly.
  4. Dip switches: Have the dip switches been set correctly?
  5. Check the valves: Ensure that the gas solenoid valves are not open or short-circuited.
  6. Inspect the burners: Make sure the burners are correctly positioned and are not clogged by dirt or debris.

Error Code 12

What It’s Telling You

  • The flame has failed.

The Solution

Assuming that the gas pressure and type are correct and your gas supply is on with no air in the system, check the following:

  1. Check the PC board wiring: Ensure there are no loose or damaged connections.
  2. Power supply: Make sure there isn’t a loss or dip in power supply.
  3. Flame rod: Confirm that the flame rod is connected and has no build-up of carbon.
  4. Gas solenoid valve: Verify that it is not short-circuiting.
  5. The burner: Clean away any debris that has built up.

Error Code 13

What It’s Telling You

  • Abnormality in combustion.

The Solution

  1. Venting system: Make sure it is correctly installed.
  2. Dip switches: Check that the dip switches are correctly set.
  3. Is there gas? Verify that the gas supply to the appliance is active.
  4. Correct pressures: Make sure the low and high fire pressures are set properly.

Error Code 14

What It’s Telling You

  • A thermal fuse fault.

The Solution

  1. Look for blockages: Check for obstructions in the venting, airflow, and water flow.
  2. Check the heat exchanger: Make sure the heat exchanger is working.

Error Code 16

What It’s Telling You

  • A warning that the appliance has overheated.

The Solution

  1. Look for blockages: Make sure the venting and airflow are not obstructed. Also check the exhaust pipe, heat exchanger, and combustion chamber.
  2. Test the water flow: Establish that the water flow is sufficient to prevent short cycling.

Error Code 19

What It’s Telling You

  • There is an error in the electrical grounding.

The Solution

  1. Test all components of the water heater for electrical short circuits (1).

Error Code 25

What It’s Telling You

  • The condensate trap is full.

The Solution

  1. Drain line: Check for a blockage in the condensate line.
  2. Ascertain the air gap: Make sure there is a gap between this line and where the drain line leaves the unit.
  3. Check for damage: Look for any loose, damaged, or broken connections between the condensate sensor and PC board.
  4. Error code persists: If the tank drains properly but the error code still appears, replace the condensate sensor.

Error Code 30

What It’s Telling You

  • Detection of flammable vapors.

WARNING!

If you see this error code, call in professionals to check that the area is free from flammable vapors before attempting any maintenance (2).

The Solution

  1. Check for damage: Check the sensor for damage or any loose connections.
  2. The code reappears: If the system has been restarted and the problem persists, replace the sensor for flammable vapor.

Error Code 31

What It’s Telling You

  • Burner sensor (thermocouple) failure.

The Solution

  1. Check the manifold and dip switches: Make sure the manifold for low or high fires and the dip switches are correctly set.
  2. Test the thermocouple: Check that the specification range of milli-volts is correct.
  3. Replace the part: If everything else is correct, replace the burner sensor.

Error Code 32

What It’s Telling You

  • There is a fault with the outgoing water sensor (thermistor).

The Solution

  1. Look for damage: Check the sensor for loose or damaged connections.
  2. Check the ohms: Ensure resistance readings are within specifications.
  3. Descale: Clean any scale from the sensor.
  4. Replace the thermistor: Replace the outgoing water sensor.

Error Code 33

What It’s Telling You

  • Outgoing heat exchange temperature sensor fault.

The Solution

  1. Check for damage: Make sure there are no loose or damaged sensor connections.
  2. Test resistance: Check that the readings are within specifications.
  3. Descale: Clean any build-up.
  4. Replace the sensor: Replace the heat exchange temperature sensor.

Error Code 34

What It’s Telling You

  • Faulty air temperature sensor for combustion.

The Solution

  1. Check for damage: Look for loose or damaged sensor connections.
  2. Test resistance: Make sure the sensor is within specifications.
  3. Descale: Clean any build-up from the sensor.
  4. Examine the fan blade: Is it secure and in good condition?
  5. Change the part: Replace the air temperature sensor.

Error Code 35

What It’s Telling You

  • Faulty tank temperature sensor.

The Solution

  1. Check for damage: Look for loose or damaged sensor connections.
  2. Resistance: Make sure readings are within specifications.
  3. Clean: Remove build-up from the sensor.
  4. Change the part: Replace the tank temperature sensor.

Error Code 52

What It’s Telling You

  • Faulty modulating solenoid valve (POV) signal.

The Solution

  1. Inspect for damage: Check the valve connections for loose or broken wires.
  2. Resistance: Make sure readings are within specifications.
  3. Check the voltage: Ensure the voltage is correct for the POV valve when the unit is firing up.
  4. Change the PC board: If the voltage is correct and the error code still appears, change this board.

Error Code 58

What It’s Telling You

  • Faulty secondary heat exchanger.

The Solution

  1. Damage: Check for broken or loose sensor connections.
  2. Descale: Inspect the heat exchanger and clean or flush it according to your owner’s manual.
  3. Prevent future scale build-up: Treat your water if it has high mineral content.

Error Code 61

What It’s Telling You

  • Faulty fan motor for combustion.

The Solution

  1. Check for damage: Look for broken or loose connections on the wiring harness for the fan.
  2. Check for free movement: Make sure the fan moves freely and the blower is intact.
  3. Obstructions: Inspect the fan housing and ensure nothing is restricting its movement.
  4. Winding resistance: Ensure the levels of the fan are correct.
  5. Replace parts: If there are issues with the fan, replace it. If the fan works properly, you might need to replace the PC board.

Error Code 65

What It’s Telling You

  • There is a fault in the water flow control. The valve hasn’t closed properly when using the bath fill function.

The Solution

  1. Disconnect the water: Turn off the water and stop the fill function immediately.
  2. Call for service: Get the unit serviced by a qualified professional.

Error Code 70

What It’s Telling You

  • Faulty PC board.

The Solution

  1. Damage: Check for broken or loose connections on the PC board.
  2. Dip switches: Ensure the dip switches are correctly set.
  3. Replace parts: Replace the PC board.

Error Code 71

What It’s Telling You

  • Faulty solenoid valve circuit.

The Solution

  1. Damage: Check for broken or loose connections on the SVO through to SV4 solenoids on the gas valve.
  2. Moisture: Ensure there is no moisture in the plastic tubes on internal units.
  3. Renew the gas valve: If there is moisture, replace the gas valve.
  4. Resistance: Check and measure the ohms.
  5. Replace parts: If the above steps don’t work, you might need a new PC board or gas valve.

Error Code 72

What It’s Telling You

  • Faulty flame sensing device.

The Solution

  1. Damage: Check for broken or loose connections on the flame rods.
  2. Flame rod: Make sure the flame rod touches the flame when it fires. Remove and inspect it, cleaning away any carbon build-up if necessary.
  3. Burner: Check for debris, which can cause a short circuit.
  4. Parts replacement: Consider replacing the flame rod gasket, flame rod, or control board.

Error Code 73

What It’s Telling You

  • Faulty burner thermocouple.

The Solution

  1. Damaged burner thermocouple wires: Check for broken or loose wire connections.
  2. Dip switches: Make sure the dip switches are correctly set.
  3. Replacement parts:  Replace the control board or burner thermocouple.

Error Code 79

What It’s Telling You

  • There is a water leak.

The Solution

  1. Damage: Check for broken or loose connections to the leak sensor.
  2. Water leaks: Inspect the piping and heat exchanger. If there aren’t any leaks, dry out the cabinet and the leak sensor and then restart the unit.
  3. The error code is still showing: Disconnect the sensor and start the heater.
  4. Replace parts: If the appliance works without the sensor, replace it.

Error Code FE

What It’s Telling You

  • Detection of flammable vapors.

WARNING!

Before attempting any work on the appliance, call in professionals to check that the area is free from flammable vapors.

The Solution

  1. Damage: Make sure the sensor for flammable vapors is intact and has no broken or loose connections.
  2. Restore power: When you’re sure flammable vapors aren’t present, turn the gas and power on.
  3. Check the system: Open a hot water faucet to start the heater up.
  4. The code has not cleared: Replace the sensor and, if necessary, the control board.

Error Code FF

What It’s Telling You

  • A repair or maintenance has been performed on the system.

The Solution

  1. When a qualified technician performs maintenance on your water heater, this code will be shown. This is so you can identify new codes that appear after a service. The system stores the nine most recent error codes. To view them, press and hold the on/off button and use the up/down buttons to scroll.

Error Code LC

What It’s Telling You

  • There is a build-up of limescale.

The Solution

  1. Check the manual: Follow the manufacturer’s recommended process for flushing the system.
  2. Temporary reset: You can reset the code temporarily by pressing the on/off button five times. This will allow the heater to work for about 70 hours before initiating the code again, which prevents the unit from working.

FAQs

Why Is My Rinnai Water Heater Not Working?

Rinnai tankless water heater troubleshooting is usually very straightforward, thanks to the user-friendly error code system. When something goes wrong with your heater, a code will be shown on the digital display. We have taken a closer look at those codes in this article. If you have no hot water but no error code, there might be an issue with the supply to the unit, rather than the unit itself. In these situations, you should call for professional help.

Why Is My Rinnai Water Heater Beeping?

In addition to displaying an error code on the digital display, your Rinnai water heater might beep to alert you to any issues. This is understandable, as you could easily go weeks without looking at your boiler’s digital display, potentially missing any issues when they arise. If your heater is beeping, check the digital display for an error code and you should be able to identify the problem quickly.

How Do I Clear Error Codes on a Rinnai Water Heater?

In most cases, you will need to resolve the issue before the error code can be cleared, allowing you to continue using your unit. If the problem is less urgent, such as a buildup of scale, you can temporarily clear the code by pressing the on/off button five times. This will allow you to use the heater for about 70 hours before the code reappears. You shouldn’t ignore these codes, as even scale build-up can become a serious issue.

How Long Do Rinnai Tankless Water Heaters Usually Last?

Rinnai water tankless water heaters usually last up to 20 years. The quality of the water, how much of it is used, and how well it is maintained all have an effect on actual life.

When compared to a tank water heater, a tankless water heater has a lifespan that is roughly twice as long, making it a more cost-effective investment in the long term.

What Is the Most Common Problem With Rinnai Tankless Water Heaters?

The most common problem with Rinnai tankless water heater is having no hot water when you try to shower. First you should double-check that the water heater is receiving the appropriate amounts of gas, electricity, and water.

Check to see that the valve that shuts off the water is not closed.

Be sure to inspect the gas burner and determine whether or not the flame rod produces sparks when the machine is activated. If not, you should read this post because it addresses the problem of the ignition failing.

Check the control panel of the unit to see if there is an error number shown there that prevents the heater from operating until the prior problem has been resolved and the system has been reset.

Why Does My Rinnai Heater Keep Turning Off?

If your Rinnai heater keeps turning off, it’s most likely a problem with the heater’s thermocouple. In most cases, the thermocouple is positioned in plain view right next to the pilot light.

Conduct a thorough examination of the thermocouple to identify whether or not it is contaminated or broken in some way. If it gets soiled, turn off the gas and let the thermocouple cool down.

Even if the pilot light was functioning normally, the valve will close if the thermocouple is faulty and needs to be replaced.

In addition to this, you won’t have the ability to manually open the valve. If such is the case, the thermocouple needs to be replaced by a trained and experienced HVAC technician.

The soot on the thermocouple will prevent the flame from reaching it, which will result in the thermocouple not functioning correctly. Gently use a wire brush and remove any soot.


Feedback: Was This Article Helpful?
Thank You For Your Feedback!
Thank You For Your Feedback!
What Did You Like?
What Went Wrong?
Headshot of Peter Gray

About the Author

Peter Gray

Peter has been a homeowner for 35+ years and has always done his own repair and improvement tasks. As a retired plumber, Peter now spends his time teaching others how they can fix leaks, replace faucets, and make home improvements on a budget.