How to troubleshoot Rinnai water heaters successfully with these Rinnai error codes. Find the most common problems and find out how to fix them.
Rinnai water heaters are among
the most advanced tankless appliances in
North America; they are made of the quality materials, have the
advanced features as can be seen in this Rinnai review and
One of the neat features that come with any Rinnai tankless
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 due to the unit's malfunction. With most of the error
codes, the unit will turn itself OFF.
Rinnai water heaters are smart, there are using the self-diagnostic tool to check its operation constantly. When the problem is detected 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.
The temperature controller MC-91 can be found on the following Rinnai water heaters: V65, RL75, V75, RL94, RU80 (RC80) and RU98 (RC98) as the standard feature, integrated into the front panel, while for the outdoor models it is not built-in but is provided. If you require additional functions, which are present on other temperature controllers you can buy them separately.
If your water heater is connected to MC-91 or MCC-91 you can easily find the most recent error codes. Press and hold the ON/OFF button for two seconds and press the arrow "UP", the last nine Rinnai error codes will appear and flash one after the other.
Note: I will assume that your Rinnai water heater was installed professionally, by the licensed technician. Keep in mind that two different problems with two different Rinnai error codes can be solved by using the same procedure.
Problem: Water heater burner does not operate in freeze protection mode.
Solution: Call a licensed technician.
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, and the error code 03 appears on the controller.
Solution:Turn OFF water flow on hot water tap. Press ON/OFF two times.
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 make sure that nothing blocks the venting system or fan, and that dip switch and condensation collar are set properly.
Problem: Rinnai water heaters are equipped with the electronic ignition, so what went wrong if there is no ignition on the gas burner.
Solution: I will assume that gas type and gas pressure are correct, that there is no problem with the gas supply and that there is no air in the gas line, correct grounding...
So, 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 gas solenoid valve for the short circuit.
Problem: Rinnai error code 12 is usually associated with the flame failure. Where is the problem if you gas water heater was working and suddenly loses the flame?
Solution: Since your water heater was professionally installed and was working for some time, I will have the same assumption as with 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. Make sure there is no obstruction in the venting system that gas combustion chamber gets enough fresh air, and the unit vents the gases out correctly.
Problem: Thermal fuse reacts due to an 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 are there any foreign materials in combustion chamber or scale build-up in the heat exchanger. Is the heat exchanger in a solid state or there are signs of breaking?
Solution: Solution for the overheating are similar to the above problem with the thermal fuse, and it includes: checking the restriction in the air flow, low water flow, clogged heat exchanger and foreign materials in the combustion chamber.
Problem: Error on the burner sensor
Solution: Replace the sensor if it is faulty or the resistance value is not as recommended.
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.
Problem: Faulty heat exchanger sensor
Solution: Before replacing the faulty sensor look to fix the loose connection, check the incorrect resistance or clean the scale build up on the sensor.
Problem: Faulty combustion air sensor
Solution: Replace the faulty sensor if one of the following actions didn't bring the satisfactorily results: Make sure that the fan is working properly, measure the resistance in the sensor and clean it from the scale build-up; loose connection or damaged wiring is fixed, the restrictions in the venting system are removed.
Problem: Solenoid valve problems
Solution: Measure the resistance of the valve coil or fix the damaged or loose wiring and connections.
Problem: Fan failure
Solution: Measure the resistance on the fan motor, check the damaged or loose wiring and connections. Make sure that the fan spins freely.
Problem: Problem with the water flow control valve
Solution: Call a technician as this Rinnai error code is related to the bath fill function.
Problem: Solenoid valve problem
Solution: Replace the electronic board.
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 the sand paper to clean the deposits on the flame rod. Replace the flame rod if the above steps didn't bring the fix.
Problem: Burner sensor problem
Solution: Ensure there is no damage on the sensor wiring or electronic board. Replace the sensor if needed.
Problem: Scale build-up in 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 the display you have to 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 the water heater to keep running.
Keep in mind that the above Rinnai error codes might help you successfully to troubleshoot the problem and fix the water heater, but some of the error codes and problems can be resolved by the licensed technician only.
(Photo credit to Rinnai)