How to Troubleshoot Rinnai Water Heaters using the Error Codes

Rinnai RU tankless water heaterRinnai RU

Do you have a problem with a Rinnai tankless water heater? Is there an error code on a remote control or unit's display, and you need help to understand it for successful troubleshooting?

See what causes the unit's malfunction and error message to display and what you can do about it.

Rinnai, like other manufacturers, requires professional installation, regular cleaning, and maintenance for the proper water heating, excellent performance, and extended unit life.

This article will show you the most common error codes and problems found in almost all Rinnai water heaters, non-condensing and condensing.

Note: Keep in mind that only the licensed Rinnai technician should install and service the unit for a valid warranty.

Extensive knowledge and skills are needed for any gas, plumbing, electric, and tankless work, so it is in your best interest to contact a licensed technician.

Common problems found on Rinnai water heaters

Hard water

One of the most common issues many homeowners are dealing with in on-demand water heating is exposure to hard water. The high concentration of mineral deposits in water is the leading cause of the sediment build-up, especially in the heat exchangers.

Rinnai tankless heaters are equipped with the "Scale Control System" that provides limescale and corrosion protection. If the problem occurs, you will notice the error code LC0-LC9, representing the scale buildup problem inside the heat exchanger.

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Water flow

Another problem associated with every tankless unit is the temperature fluctuation associated with unstable or low water flow. The variation of hot water temperature usually happens when two or more fixtures are operating simultaneously.

The unit must have the minimum flow reached; otherwise, you might have the problem even with the slightly lower water flow than the minimum required. By increasing the flow rate, the problem can be solved.

Troubleshooting Rinnai water heaters are much easier if they come with the diagnostics system. Units equipped with the remote controller, such as the MC-91-2, will provide the most recent diagnostics information and allow you to react immediately by recognizing the error code and following the troubleshooting guide.

Error Codes Guide

Again, the recommendation is to contact a licensed technician for troubleshooting and any work that needs to be done on the water heater. If planning to do it yourself, use the following suggestions carefully. Some error codes can be fixed only by the professional.

Also, remember safety first. It will be assumed that the installation was done correctly. This is also important to do: check the length of the venting system, ensure that the water heater is using the correct gas type, check that the pipes are appropriately sized...

Error Code 03 - Bath Fill problem

Bath Fill function is disturbed after the power outage. You should turn the hot water taps OFF and press the power button twice to resume the Bath Fill.

Error Code 10 - Vent blockage

Check the venting system (both intake and exhaust) for the obstructions. A detailed guide on how to troubleshoot error code 10 is explained here.

Error Code 11 - No ignition

When there is no gas ignition, the heater is OFF. Test the igniter and see if it is still working. This includes checking the loose connections, damaged wiring harness, and removing the deposits from the electrodes. Check the burner and clean it if necessary from the dirt and debris (also condensation).

Are all electric elements properly grounded, and does the gas valve have short circuits? Read more about an error code 11.

Error Code 12 - No flame

If there is no flame, use some of these tips for troubleshooting: check the loose connections and the proper voltage on the power supply, PC board, and igniter. Ensure that the gas burner is not clogged and the igniter does not contain carbon buildup.

Get more details on how to troubleshoot error code 12.

Error Code 14 - high temperature

The thermal fuse has been activated due to the high temperature in the combustion chamber and venting. Ensure that there is no blockage in the vent system (lack of combustion air). Clean or replace the heat exchanger if it is dirty, has the scale buildup, debris burning, or is damaged. Increase the water flow if it is too low.

Error Code 16 - the unit is too hot

The over-temperature sensor reacts if the unit is too hot, so it shuts the unit down. Make sure that problems such as those found when dealing with the error code 14 are resolved.

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Error Code 19

Make sure that the electrical grounding is done correctly and there are no shorts.

Error Code 32 and 33 - water temp. sensor

If there is a problem with the outgoing water temperature sensor or sensor on the heat exchanger, check the resistance of the elements, ensure that the wiring is not loose, clean the elements from deposits or replace them if damaged.

Error Code 34 - combustion air temp. sensor

The problem of venting or air supply. Ensure that your water heater gets enough combustion air and that the vent system is not blocked. Ensure that the fan is operating correctly, that a sensor is not damaged, or wire connection is loose. Check the resistance of the sensor.

Error Code 41 - temperature thermistor

This code is found on the outdoor models only. Use the same approach as with other sensors above.

Error Code 52 - solenoid valve problems

Make sure that the valve coil resistance is OK and that the wiring harness is not damaged and connections lose.

Error Code 57 - burner problem

Ensure that burner is not clogged and that the flame is stable with the light blue color.

Error Code 61 - fan problems

Check the resistance of the fan motor, that it is turning freely, and there is no damaged wiring or loose connections.

Error Code 65 - water flow problem

Replace the water flow sensor if it is broken.

Error Code 70 - issues with the PC board

Make sure that the PC board gets the electrical power without any obstructions. If it is damaged, replace the board. Also, replace the board if you get the error code 71, which indicates the problem with the solenoid valve circuit.

Error Code 72 - flame sensor

Make sure that the flame sensor is touching the flame. If there is limescale buildup, use the fine sandpaper and clean it. All the wiring should be without damages, and connections must be tight. Replace the element if it is needed.

Error Code 79 - water leak

Check the internal elements and plumbing for leakage.

Error Codes LC0 - LC9 - scale buildup

Error Code FF - maintenance performed

The error codes mentioned above were taken from the manufacturer instructions, so troubleshooting Rinnai becomes easier and convenient for readers of this website. Keep in mind that the warranty does not cover the unit if the problems were related to freezing, water quality, flooding, fires, improper installation, or handling.

To provide reliable and efficient long-term operation of your Rinnai water heater, have it installed by a pro. You can contact a plumber here. Also, to repair any of the problems, such as those shown in the above error codes, a licensed professional should be contacted.

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