All Rinnai Error Codes For Your Tankless Gas Hot Water System Explained.

As an electrician, I am often called out to repair tankless hot water systems. Often it is an easy fix with the Rinnai error codes displayed. Interpreting these codes is another matter.

With a proper serviced Rinnai gas hot water system you can have up to 20 years of trouble-free running. They are a very reliable unit.

Please take care when working around gas and electricity. You must be licensed to perform any electrical and gas fitting work. Before commencing any Diagnostic Procedure – Turn off the power source to a unit. Turn off the gas supply.

Rinnai error code 00

Power failure when in standby/on mode. Switch the gas heater to standby then on again.

Rinnai error code 02

No burner during freeze protection mode. Check gas and water supply. Also, check that the outlet flue is not blocked and that the primary air fan is rotating freely. Turn off the Rinnai hot water unit for 30 seconds. Turn it back on to reset the fault code. Run a hot tap to see if the tankless gas hot water unit starts up.

Rinnai error code 03

Power disturbance during Bath Fill (Water does not flow when power returns) This is a safety feature. First, turn off all the hot water taps and then press the ON & Off button. This will turn the hot water system back on and reset the fault.

Rinnai error code 10

Air Supply, Flue, or Exhaust Blockage. Visually check for leaves, sticks, rodents, or other foreign matter. Make sure Rinnai-approved venting materials are used with the correct sizing.

As well as cleaning all vents, and pipework you should remove the dirt-trap. This is located inside the gas hot water unit on the air inlet side. It will just pull out.

Rinnai error code 11

Rinnai error code 11 is an indication that there is no ignition or no gas supply to your hot water system. You can try the following to fix the problem:

• Check your hot water system for any corrosion, loose parts, blocked flue, correct gas pressure, and flow.
• Locate your gas supply and make sure it is turned on.
• Test your gas supply by turning on another gas appliance, such as a stove top.
• Check whether the dip switches are properly set according to the user manual.
• The code is no ignition and can be either a gas problem, vent problem, or a ground problem.
• Sometimes it can be solved by just cleaning the fan, ignitor, or flame rods.

Rinnai error code 12

 Error Code 12 indicates a flame failure on a Rheem tankless water heater.

• Check out all gas valves and see if they are open and if the gas supply to the system is all right.
• See if the flame rod wire is connected and not corroded.
• Inspect the flame rod and see whether it has carbon or dirt accumulation on it. Isolate power and clean the element.
• Check that gas, air (fan), and electricity for correct operation.
• Check for a blue flame. If it is yellow or orange you may have a flame issue.

Rinnai error code 13

When an Error Code 13 improper or faulty combustion within the flame rod.

[Note: An Error Code 13 will only show on the indoor Rheem tankless system.]

• Inspect if the air intake and exhaust system are correctly installed and are in good working condition. Look for blockages and foreign matter. It is important that the exhaust gasses are not recirculating into the system’s clean air intake.
• Check and confirm if the altitude settings point to your location.
• Inspect the Flame Rod FL-24.
• Inspect the Blower Motor.
• Check the dip switches on the PCB are correct according to the user manual.
• Check for a blue flame. If it is yellow or orange you may have a flame issue.

Rinnai Error Code 14

When an Error Code 14 is an overheat wrap fault.

If the system has free (unclogged) airflow and venting you can check for the following:

• Inspect high and low fire pressure sensors.
• Check and confirm if the right type of gas is used.
• Check the heat exchanger and see if there are any cracks and separations.
• Inspect to ensure there aren’t restrictions to the airflow that is entering the system and no restrictions at the vent terminal.
• Inspect for any presence of foreign materials in the combustion cavity and exhaust piping.
• Inspect the heat exchanger. Look for cracks and separations. Check that there are no restrictions to the airflow entering the unit and no blockages at the vent terminal. Check the combustion chamber and the exhaust piping for foreign materials.

Rinnai Error Code 15

Venturi Control

• Ensure the Venturi fan motor is operating correctly.
• Replace the gas valve assembly.
• Clear the diagnostic code by resetting the main power supply to the water heater. Turn it off for 30 seconds and then back on.
• Check for a blue flame. If it is yellow or orange you may have a flame issue.

Rinnai Error Code 16

Rheem tankless water heater error code 16 indicates over temperature warning. This is a safety shutdown because the unit is too hot.

It is quite a common shower water temperature problem when the water is hot and then cold a few minutes later. The unit has overheated and then tripped out.

• Check for restrictions in airflow around the unit and vent terminal.
• Confirm fan motor is functioning correctly.
• Check for low water flow in a circulating system causing short cycling.
• Check for foreign materials in the combustion chamber and/or exhaust piping.
• Check for blockage in the heat exchanger.
• Inspect for any blockages or limescale accumulation in the heat exchanger.
• Check and ensure there aren’t airflow restraints to the system, and that the vent terminal is free and not blocked.
• Inspect the outlet thermistor.
• Check the thermistor of the heat exchanger for damage, short circuit, or open circuit.
• Replace the gas valve assembly.

Check out the following video that explains how to test thermistors with a multimeter.

Rinnai Error Code 17

Venturi Blockage

• Ensure Venturi and fan ducting aren’t blocked.
• Check that the fan is rotating freely.
• Check that there is power going to the fan.
• Call Rinnai technical department.

There are many different types of fans for Rinnai tankless hot water systems so just look for a fan. Use a screwdriver to try and turn the fan blades gently.

Rinnai Error Code 19

Electrical Grounding issue. This means there could be a short circuit to earth from inside the tankless hot water unit. Check all components for an electrical short circuit.

Remove any moisture from inside the Rinnai unit. Clean any corroded terminals and insulate any exposed or cracked cables. Check for any corrosion on the PCB and good earthing.

Rinnai Error Code 21

Data Transfer Error or Error Code 21 indicates a failure of the air intake filter switch. If the PCB has been replaced, ensure the data transfer process has been completed.

• Inspect if the air filter door is seated fittingly.
• Inspect if the front panel is correctly installed.

Rinnai Error Code 24

Error Code 24 is a switch malfunction.

• Turn Off the water and unplug the remote control; then retry.
• Double-check if the tankless water heater is appropriately grounded.
• Press the minimum (MIN) and maximum (MAX) buttons on the control board (PCB) together to reset.

Rinnai Error Code 25

The condensate Pump (Accessory) Trap is Full. Inspect that the condensate pipe is not blocked and is in working condition.

• Confirm wire connections and harness are good with no corrosion.
• Ensure the condensate reservoir is empty and the condensate pump is operating. Glue the condensate put pipework if you need to dismantle it to inspect for blockages.

Rinnai Error Code 29

Error Code 29 on a Rheem tankless water heater, indicates the temperature on the heat exchanger is very low. Or it could signal that the neutralizer is choked on a condensing unit.

When you get this error code, do the following:

• Clean the screen of the air inlet.
• Clean the heat exchanger’s fins.

After doing the above if you’re still getting this error code on your Rheem tankless model, then check the following:

• Check the drain line for any obstruction and ensure the shipping cap is removed.
• Inside the unit, clear all the drainage ports of the neutralizer.
• Outside the unit, clear the drainage line of the neutralizer.
• Check for a blue flame. If it is yellow or orange you may have a flame issue.

Rinnai Error Code 31

Error Code 31 Rinnai water heater indicates a fault in the temperature sensor of the water inlet.

Check the following:

• Check the wiring of the thermistor for damage.
• Inspect to find out if the thermistor is free of limescale accumulation. Clean if required.
• Ohm reading of the thermistor using a multimeter.
• A short circuit is a failed thermistor.
• Replace sensor.

Rinnai Error Code 32

Error Code 32 on your Rinnai water heat indicates a malfunctioning or faulty outgoing water temperature sensor (thermistor).

Turn off the power source to the hot water unit. Turn off the gas supply.

• Check the temperature with a thermometer at the closest hot water tap or the exit hot water tank outlet.
• Ensure there are no loose, broken, or damaged connections on the thermistor.
• Examine resistance readings to ensure they are within the required specs.
• Scrutinize for scale accumulation on the thermistor.
• Check and test the sensor (thermistor) – if it’s found faulty, then replace it. A short circuit is a faulty thermistor.

Rinnai Error Code 33

Heat Exchanger Outgoing Sensor error

Error Code Remedy

• Check the sensor wires for corrosion.
• Replace the sensor.
• Check sensor wiring for damage.
• Measure the resistance of the sensor.
• Clean the sensor of scale build-up.

Rinnai Error Code 34

Combustion air temperature sensor malfunction

Error Code Remedy

• Make sure the unit’s fan blade is tight on the motor shaft and is in working condition.
• Check for restrictions in airflow around the unit and vent terminal.
• Inspect the sensor wire damage and corrosion.
• Measure the resistance of the sensor.
• The clean sensor of scale build-up.

Rinnai Error Code 38

Exhaust Thermistor CO Sensor

• For your safety and the health of your equipment, the CO Sensor is very important. Exhaust gasses are fatal if not vented out to the atmosphere correctly. Carbon monoxide (CO) sensing in the Rinnai exhaust is a build-up over the recommended level. Unburnt natural gas is a problem that could cause an explosion.

• Check sensor wiring for damage.
• Measure the resistance of the CO sensor.
• Clean the sensor of scale build-up.
• Replace sensor.
• Check for a blue flame. If it is yellow or orange you may have a flame issue.

Rinnai Error Code 41

Freeze Protection Sensor

• Turn the hot water tap On & Off along with pressing the On/Off button on the system monitor.
• Check sensor wiring for damage.
• Measure the resistance of the sensor. A short circuit is a failed sensor.
• Clean the freeze protection sensor of scale build-up.
• Replace sensor.

Rinnai Error Code 51

Inlet Water Temperature Thermistor (Sensor)

• Check sensor wiring for damage or corrosion.
• Measure the resistance of the sensor. A short circuit is a failed sensor.
• Clean the sensor of scale build-up.
• Replace sensor.

Rinnai Error Code 52

Modulating Solenoid Valve Signal Error fix

• Measure the resistance power of the solenoid winding. A short circuit or ground fault is a failed solenoid valve.
• Inspect modulating gas solenoid valve wiring harness for damaged terminals.

Rinnai Error Code 57

Burner Overheat Bi-Metal Switch Failure

Error Code Remedy

• Check the power outlet of the unit working accurately.
• Check the gas supply working correctly.
• Turn the hot water tap On & Off.

Rinnai Error Code 58

Error Code 58 on your Rinnai water heater indicates a secondary heat exchanger sensor fault. This could either be a short or open circuit. Or just out of range.

Before commencing any Diagnostic Procedure – Turn off the power source to a unit. Turn off the gas supply.

• Code displays when one of the two bi-metals opens at the back of the secondary heat exchanger.
• Inspect and test the sensor.
• Check voltage.
• Inspect wiring harness electrical connections.
• Ensure there aren’t any loose, broken, or damaged connections at the sensor wiring harness.
• Check and clean the heat exchanger for any debris particles and insects, and flush the system clean.
• If there is scale build-up in the secondary heat exchanger it needs to be flushed to prevent damage. Refer to the flushing instructions in the manual. Hard water must be treated to prevent scale build-up or damage to the heat exchanger.
• Inspect for scale accumulation on the heat exchanger and flush if required.
• Apply hard water to protect from scale accumulation in the future.

Rinnai Error Code 61

Error Code 61 on your Rinnai water heater is a combustion fan motor malfunctioning or defective flow.

Before commencing any Diagnostic Procedure – Turn off the power source to a unit. Turn off the gas supply.

• Check the wiring harness.
• Check fan speed revolution.
• Inspect the airflow.
• Check for any internal damages.
• Ensure there aren’t any loose, broken, or damaged connections on the fan motor wiring harness.
• Remove the fan motor and inspect the blower wheel, to make sure it turns freely.
• Inspect the fan shell for any barriers. Measure fan motor rolling resistance.
• If windings are within specs, change the PC board.
• If the windings shorted out, change the motor.

Rinnai Error Code 63

Rinnai Error Code 63 is a recirculation low flow. The circulation Flow Rate dropped below 1.3 GPM.

• Ensure the bypass plug is removed and the bypass filter is installed. (Crossover Mode)
• Ensure both the inlet water filter and bypass filter are clean and free of debris.
• Ensure Parameter settings are correctly set for recirculation mode.
• Check the pump supply voltage.
• Ensure air is removed from the recirculation line, if not purged.
• Check for frozen pipes.
• Check for scale buildup.

Rinnai Error Code 65

Error Code 65 on your Rinnai water heater indicates water-flow control abnormality. The water flow control valve has failed to close during the bath fill function. Immediately turn off the water and discontinue the bath fill function.

Before commencing any Diagnostic Procedure – Turn off the power source to a unit. Turn off the gas supply.

• Inspect the internal water valve controller.
• Check the inlet water valve filter.
• Check water-flow kPa pressure.
• Make sure there aren’t any loose, broken, or damaged connections on the water-flow servo.
• Switch off the power to the unit and then switch it on again, and check if the code goes away.
• If you see the code coming back, then place a service call for an expert technician.

Rinnai Error Code 70

Error Code 70 on your Rinnai hot water system means there is a fault with the main PCB board. It is best for an electrical technician to diagnose and replace this part.

Before commencing any Diagnostic Procedure – Turn off the power source to a unit. Turn off the gas supply.

• Possible fault with the PCB board.
• Make sure there aren’t any loose, broken, corroded, or damaged connections on the PCB board.
• Ensure dip switches are set appropriately.
• Moisture on the PCB board. Dry with a hairdryer.
• You will need to replace the PCB board, which is something that should only be done by qualified and experienced technicians.

Rinnai Error Code 71

Rinnai Error Code 71 is a solenoid valve circuit fault.

Error code fix.

• Inspect the resistance power of each solenoid valve coil. You may have a water and gas inlet valve.
• Check the wiring harness of all solenoids for loose connections.
• Replace the PCB board and solenoid valve.
• Check for short circuits on the solenoid valve and or moisture on the PCB board.

Rinnai Error Code 72

Rinnai Error Code 72 is caused by a Flame Sensing Device Error.

Error Code Fix Procedure

• Replace the flame rod.
• Make sure the flame rod is contacting the flame when the Rinnai unit fires up.
• Remove the flame rod and check for carbon build-up. If found then clean it with a scouring sponge.
• Ensure the flame rod is touching the flame when the unit fires.
• Check all wiring to flame rod for damage.
• Check inside the burner chamber for any foreign material blocking flame at the flame rod.
• Measure micro amp output of sensor circuit with the flame present.

Rinnai Error Code 73

Rinnai Error Code 73 is a fault in the burner sensor circuit.

Error Code fix procedure.

• Change the sensor.
• Inspect sensor wiring for cracks and corrosion. Check PCB board for loose connection.

Rinnai Error Code 79

Error Code 79 on your Rinnai hot water system is a water leak detection inside the unit. This is detected by a sensor on the bottom. It can be caused in high humidity environments when there is a lot of condensation.

Before commencing any Diagnostic Procedure – Turn off the power source to a unit. Turn off the gas supply.

• A water leak has been detected inside the unit.
• Check water leak on connections o-rings gaskets.
• Check water inlet manifold.
• Make sure there aren’t any loose, broken, or damaged connections on the leak detector.
• Inspect the heat exchanger and all piping for leaks.
• If you can’t spot any leaks, wipe out the water that is inside the cabinet, dry out the leak sensor, and restart the system.
• If the error code comes up again, then disconnect the sensor and start the water heater.
• If the system runs without the sensor, then you need to replace the water leak sensor and the screw.

The water leak sensor is located on the bottom metal part of the gas hot water unit.

Rinnai Error Code LC, LC1, LC2, 00

Scale Build-up in Heat Exchanger (when checking maintenance code history, “00” is substituted for “LC”)

NOTE: The LC code is the only error code that will allow the unit to keep running. The display will alternate between the LC code and the temperature setting. The controller will continue to beep. The LC code will reset if the power is turned off and then on.

• Flush heat exchanger with white vinegar or Flow-Aid Flushing Fluid. A tank less hot water flushing kit is a fast way to clean the scale. Refer to the instructions in the manual or video shown below.
• Replace the heat exchanger.
• LC0-LC9 indicates that there is scale build-up in the heat exchanger and that the heat exchanger needs to be flushed to prevent damage. Refer to the flushing instructions in the manual. Hard water must be treated to prevent scale build-up or damage to the heat exchanger.
• To operate the water heater temporarily until the heat exchanger can be flushed, push the On/Off button on the temperature controller 5 times. Repeated LC codes will eventually lock out the water heater.
• Water has been detected at the bottom of the unit. Turn off the water supply.
• Check all plumbing internally for leakage.

Rinnai Error Code SS

• SS is a time-based service indicator set during installation.
• See section “3.12 Parameter Settings” for additional details on setting and changing the SS indicator.
• SS indicates that it is time for service. The heat exchanger should be flushed to prevent damage (refer to section Flushing the Heat Exchanger for more information).
• Hard water must be treated to prevent scale build-up or damage to the heat exchanger. Scale is most often a problem when water is heated up.
• To reset the SS code, push the On/Off button on the temperature controller 5 times in 5 seconds.

Rinnai Service procedure

• Clean the inlet water supply filter.
• On new installations ensure hot and cold water lines are not reversed.
• Check for leaks.
• Isolate the unit from the building by turning off the cold water line to the building or the Rinnai hot water unit.
• Isolate the circulating system if present. Open your pressure relief valve; if water is flowing, there is bleed over in your plumbing.
• Ensure you have at least the minimum flow rate required to fire the unit.
• Check for scale build-up and flush the Rinnai hot water unit using white vinegar or use a tankless water heater flushing kit.
• Ensure the fan turbine spins freely.
• Measure the resistance of the water flow control sensor.
• Check for DC shorts at components.
• Check for moisture inside the tankless hot water unit.

Rinnai Water Heater Not Working After Flush/Descaling In-use light not on

This is a problem that is starting to come up after people are flushing their hot water system without a water filter in place. There is a little flywheel/pinwheel mechanism that detects the hot water flow so that the gas can be fired up.

Sometimes this gets stuck or clogged up and will require a service technician to come out. But it can be fixed yourself with some needle nose pliers or a can of compressed air.

Turn off the water supply and remove the two screws to the filter housing. Use needle-nose pliers to pull down the black cylinder pinwheel. Make sure it is spinning freely. Replace the water filter unit.

The following video explains it well.

Conclusion

I have worked on many Rinnai and Bosch tankless hot water systems over the last 20 years. Often it is an easy fix due to water ingress or a worn-out cable or sensor.

I find that most of the time a good flush out will fix a lot of the heating issues. Scale build-up will cause your gas heater to run hotter to try and achieve the correct temperature setting.

So don’t get a new hot water system just flush it out if the hot water system has an over or under-temperature warning. Do the flush every 2 years and you will have no issues.

Here is the full Bosch tankless hot water error codes list for those that need them.