Rinnai Error Codes and
Troubleshooting guide

Rinnai tankless water heaterRinnai

How to troubleshoot Rinnai water heaters successfully with the Rinnai error codes. Explore the most common heater's problems and find out how to fix them. How to contact a plumber and get help!

Rinnai water heaters are among the most advanced tankless appliances in North America; they are made of quality materials, include advanced features as can be seen in this review, and utilize very sensitive elements.

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One of the neat features that comes with any Rinnai tankless water heater is the temperature controller, which allows you to set the temperature of the outgoing hot water and see one of many Rinnai error codes that appear when there is a problem.

With most error codes, the unit will turn itself OFF.

Rinnai water heaters are smart; they use the self-diagnostic tool to check the operation regularly. When the problem is detected, the error code flashes at the temperature display on the following models: MC-91, MCC-91, and MC-502, while it flashes at the clock display on models MC-100 and BC-100.

Keep in mind that today's modern tankless water heaters, including models from Rinnai, due to the complex design, require a lot of knowledge and skills for the repair of the faulty element.

Before making an expensive service call or spend time and money to fix it, contact a company networx.com that will connect you with professional plumbers and provide you with up to 3 FREE Quotes.

Rinnai error codes explained

Did you know that the licensed plumber will ensure that your water heater is permitted and up to code upon installation! 

Contact your local professional water heater expert today!

The temperature controller MC-91 is found on Rinnai water heaters as the standard feature, integrated into the front panel, while with the outdoor models is provided with the purchase. You can also buy advanced temperature controllers to get some additional functions.

You can easily find the most recent error codes if your water heater is connected to MC-91 or MCC-91. Press and hold the ON/OFF button for two seconds and press the arrow "UP," and the last nine Rinnai error codes will appear and flash one after the other.

Note: We will assume that your Rinnai water heater was installed professionally by a licensed technician. Keep in mind that two different problems with different Rinnai error codes can be solved using the same procedure.

Error Code 02

Problem: The water heater burner does not operate in freeze protection mode.

Solution: Call a licensed technician.

Error Code 03

Problem: When the BC-100 temperature controller is used for the bath fill function, there will be no water flow when the power resumes after the power outage. The error code 03 appears on the controller.

Solution: Turn OFF the water flow on the hot water tap. Press ON/OFF two times.

Error Code 05

Problem: Bypass Servo

Solution: The procedure is simple; turn the power OFF, turn the power back ON to fire up the unit. If the error code 05 is still there and shown on display, the bypass valve is broken and has to be replaced.

Error Code 10

Problem: Reduced or no air supply to the water heater or there is an obstruction in extracting the flue gases out.

Solution: Make sure that the recommended Rinnai venting is used, there is no obstruction in the venting system, no reduction in diameter and lengths are per instructions. Also, ensure that nothing blocks the venting system or fan, requested clearances are met, and the dip switch and condensation collar are correctly set.

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Error Code 11

Problem: Rinnai water heaters are equipped with the electronic ignition system, so what went wrong when there is no ignition on the gas burner?

Solution: It will be assumed that gas type and gas pressure are correct, there is no problem with the gas supply, there is no air in the gas line, and grounding is done correctly...

Make sure that the igniter generates sparks and that all the wiring connections are OK. Check the gas burner for proper installation and remove debris and dirt if you find any. Check the gas solenoid valve for the short circuit.

Error Code 12

Problem: Rinnai error code 12 is usually associated with flame failure. Where is the problem if your gas water heater is working and suddenly loses the flame?

Solution: Since your water heater was professionally installed and worked for some time, we will have the same assumption as for the above problem.

Check the loose wiring for the PC board, power supply, and flame rod. Clean the flame rod from scale build-up and burner from debris and dirt. Check for short circuits on the gas solenoid valve, reconnect all wiring connections. Ensure there is no obstruction in the venting system, that the gas combustion chamber gets enough fresh air, and the unit vents the gases out correctly.

If you require professional repair of the error code 11 or 12, contact an expert.

Error Code 14

Problem: Thermal fuse reacts due to excessive temperature.

Solution: Clean the obstructions if you find any in the venting system or water flow system. If there is not enough incoming cold water through the heat exchanger, the temperature will increase significantly. Also, see if there are any foreign materials in the combustion chamber or scale build-up in the heat exchanger.

Check for any cracks and damages on the heat exchanger.

Make sure dip switches are set to the proper position.

Error Code 16

Problem: Over temperature warning.

Solution: Clean the obstructions if you find any in the venting system or water flow system. If there is not enough incoming cold water through the heat exchanger, the temperature will increase significantly. Also, see if there are any foreign materials in the combustion chamber or scale build-up in the heat exchanger. Is the heat exchanger in a solid state, or are there signs of breaking?

Error Code 19

Problem: Electric grounding.

Solution: Check all components for electric short.

Error Code 25

Problem: Condensate trap is full.

Solution: There are several solutions for the full condensate trap, including deblocking the drain line, condensate trap, and tank, fixing or tightening the sensor wiring harness, and replacing the condensate tank with the sensor.

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Error Code 31

Problem: Error on the burner sensor.

Solution: Replace the sensor if it is faulty or the resistance value is not as recommended.

Error Code 32

Problem: Faulty temperature sensor on the outgoing water line.

Solution: Check the sensor wiring for loose connection or damage, measure the resistance or clean the scale build-up. If none of this helps, replace the sensor.

Error Code 33

Problem: Faulty heat exchanger sensor.

Solution: Before replacing the faulty sensor, look to fix the loose connections, check the incorrect resistance, or clean the scale build-up on the sensor.

Error Code 34

Problem: Faulty combustion air sensor.

Solution: Replace the faulty sensor if one of the following actions didn't bring desired results:

  • Make sure that the fan is working correctly.
  • Measure the resistance on the sensor and clean it from the scale build-up.
  • Loose connection or damaged wiring is fixed.
  • Restrictions in the venting system are removed.

Error Code 41

Problem: Freeze protection sensor in external units doesn't work.

Solution: Fix the loose, broken, or damaged sensor wiring harness, remove the obstructions and if there is no proper reading on the sensor, replace it.

Error Code 51

Problem: Freeze protection sensor in external units doesn't work.

Solution: Fix the loose, broken, or damaged sensor wiring harness, remove the obstructions and if there is no proper reading on the sensor, replace it.

Error Code 52

Problem: Solenoid valve problems.

Solution: Measure the resistance of the valve coil or fix the damaged or loose wiring and connections.

Error Code 57

Problem: Burner overheat bi-metal switch does not work.

Solution: The water heater should be set to the correct fuel type and pressure, or if the conversion was done, it was done per manufacturer instructions. Check the switch wiring harness for proper condition operation. Replace the sensor if it is faulty.

Error Code 58

Problem: Secondary (condensing) heat exchanger sensor.

Solution: Check the wiring harness for loose, broken, or damaged connections. Look for the scale build-up inside the heat exchanger and perform flushing. Take the necessary steps to reduce the effects of hard water.

Error Code 61

Problem: Fan failure.

Solution: Measure the resistance of the fan motor, check the damaged or loose wiring and connections. Make sure that the fan spins freely.

Error Code 65

Problem: Problems with the water flow control valve.

Solution: Call a technician as this Rinnai error code is related to the bath fill function.

Error Code 70

Problem: PC board fault.

Solution: Check the wiring and that all dip switches are in place. Replace the electronic board if necessary.

Error Code 71

Problem: Solenoid valve problem.

Solution: Replace the electronic board.

Error Code 72

Problem: Flame sensor failure.

Solution: Make sure that the flame sensor is in contact with the fire. Check for the damaged or loose connections and wiring. Use sandpaper to clean the deposits on the flame rod. Replace the flame rod if the above steps didn't bring the fix.

Error Code 73

Problem: Burner sensor problem.

Solution: Ensure there is no damage to the sensor wiring or electronic board. Replace the sensor if needed.

Error Code 79

Problem: Burner sensor problem.

Solution: Ensure there is no damage to the sensor wiring or electronic board. Replace the sensor if needed.

Error Code LC or OO

Problem: Scale build-up in the heat exchanger.

Solution: Water in NA is usually hard, so the lime and scale build-up is frequent. If the "LC" error code appears on display, you must clean the deposits by flushing the heat exchanger. Otherwise, replace the heat exchanger. "LC" is the only code from all Rinnai error codes that will allow a water heater to keep running.

Conclusion

Keep in mind that the above Rinnai error codes might help you successfully troubleshoot the problem and fix the water heater, but some of the error codes and issues can be resolved by the licensed technician only.

The service call and technician visits are expensive and time-consuming, so try filling out this form and get three free quotes from the local plumbers (where applicable).

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