How To Reset Rinnai Tankless Water Heater? Complete Guide 2022

If you have a Rinnai tankless water heater, kudos to you, you have made one of the wisest investments of your life. You should expect dependable performance and unlimited hot water from the unit for more than 20 years. 

Tankless devices require far less maintenance and servicing than tanked heaters, but it is still essential to maintain them properly. When they have problems, it is mandatory to know how to reset Rinnai tankless water heater

How To Reset Rinnai Tankless Water Heater?

Having troubles with your heater can be very frustrating, especially when so many people live in your house. If all the warm water fixtures are linked to the same unit, it becomes more challenging for people to manage their day. 

When you encounter any troubles with your appliance, an error code will appear on the digital display screen that will exhibit what the issue with your device is. The error code enables you to detect the problem and acquire an immediate solution. 

Our detailed guide on troubleshooting Rinnai tankless water heater will certainly help you if you are experiencing such problems.


Error Codes Of Rinnai Rankles Water Heater

Error Code 2

This code means that the burner is not functioning during freeze protection mode. 


  • You can’t fix it on your own, so it highly recommended you call a professional. 

Error Code 3

It shows that power was interrupted during the bath fill. When the power returns, the water will not flow. 


  • First of all, turn off all the outlets attached to the unit in your residence. The water should not flow out. 
  • Now, go to the temperature controller and press the On/Off button twice. It will allow the controller to how to reset Rinnai tankless water heater bleed fully. However, if the code comes back, you need to change the PC board. 

Error Code 5

It means that there is some issue with the bypass valve. 


  • Shut off the power supply to the heater and turn off all the fixtures connected to the device. Make sure the water is not flowing. 
  • Again, turn on the power and open the hot water faucet to fire up the unit. Once it is fired up, the error code will disappear. 
  • However, if it does not go away, the bypass valve needs replacement. 

Error Code 7

This code indicates that there is some issue with the water circulation flow rate. The problem occurs when the circulation flow rate is dropped below 2.1 gallons per minute. 


  • It means that the air supply or exhaust is blocked. The air supply issue can lead the appliance to severe damages.

Error Code 10

It means that the air supply or exhaust is blocked. The air supply issue can lead the appliance to severe damages. 


  • First of all, check the vent systems for any blockage and clearance problems. Make sure to check for other troubles that can prevent proper ventilation. 
  • Also, inspect the outside venting system to find out if there is any leakage or obstruction. 
  • If you can’t find or fix the issue, don’t hesitate to call the expert. 

Error Code 11

Rinnai tankless water heater code 11 means that there is no ignition in the heater. This issue is linked with the gas and gas lines, so it is better to call a plumber. 


  • Inspect the valve and the water heater, gas meter, or cylinder. All the fixtures should be shut off, but the power should be on so that you can check the deflection. 
  • Now, assess the igniters and find out if they are operating correctly or not. 
  • If it’s functioning perfectly, but you are still not getting hot water, call the professional. 

Error Code 12

This error shows that there might be a flame or electrical failure. Again, this issue is associated with gas and gas lines. That’s why; first diagnose the issue before going to the solution. 


  • Check if the flame is on through the window box of the device. If you can see a flame in the burner box, it is obvious that it is a flame failure. However, if there is no flame, it is an electrical failure. 
  • A short circuit within the PC board can be the primary reason for an electrical failure. In this situation, turn off the power to the machine, unscrew the circuit, and then look for patches and cross-connection. 
  • If you can’t assess it properly, you can call the specialist. 

Error Code 13

This code indicates that there is some issue with combustion. 


  • Inspect for the B-vent materials and check if they are correctly deployed. Then, assess the rest of the venting systems to know if they are installed correctly.  
  • The dip switches should also be checked according to the altitude. Test the inlet gas supply and fire pressures. 
  • Once you are done with the inspection, activate the heater again. 

Error Code 14

It shows that there is something wrong with the thermal fuse. 


  • For troubleshooting Rinnai tankless water heater, the bi-metal switches fixed to the heat exchanger’s top should be checked.  
  • Give some time to the unit to cool before resetting it. 
  • Next, assess the Thermo fuses that are present around the heat exchanger. If it is not operating, the switches should be replaced. 
  • To solve this issue, the heater exchanger will be removed, and thermal fuses will be changed. If you are confident to handle this job, you are good to go; otherwise, call a plumber for help.    

Error Code 16

It is not an error but an over-temperature warning. It indicates that the unit has automatically turned off to safeguard itself from damage. 


  • Check the air filter to find out if it is clean. If not, clear all the blockages in the filter. 
  • Then, remove all the clogs and blockages within the heater and also look for their positions. 
  • Assess if the venting system is obstructed; if yes, clear it. 

Error Code 19

This code shows that an electrical short exists in the wiring. This problem may occur because of a failure in electrical grounding. 


  • If you don’t know how to reset Rinnai tankless water heater, we recommend you call an expert. Until he arrives, shut off the heater, and also closes the warm water outlets. 

Error Code 25

It shows various problems, but the common one is of condensation trap. 


  • First, shut off the power and close the hot water fixtures. Then, look for any blocks in the drain line. For this purpose, you will have to open the cabinet. Then, inspect the condensate tank thoroughly to clear all the blockages. 
  • Next, again check the drain line to find out the air gap. Then, inspect the sensor wiring harness to check for the connections between the sensors and the PC board. If the error still exists, the sensor may need replacement. 

Error Code 32

It might be the problem of groundwater temperature. This code also shows up when the sensors are faulty. 


  • When this error code appears, it rapidly shut off the power to prevent damage to the heater’s body. 
  • Now, open up the machine and assess the groundwater temperature. If you can’t check the sensors, call a professional for sensor replacement. 

Error Code 33

It means that the heat exchanger is not working properly. 


  • Turn off the power and test the connections that exist inside the thermistor. 
  • Then, the readings should be checked from the resistance to confirm the specifications are good. Now, it’s time to check for the scale accumulation. Remove and clear the rust in the thermistor. 
  • You can replace the thermistor if it is still not functioning. 
How To Reset Rinnai Tankless Water Heater

Error Code 38

This code means that something is wrong with the CO sensor abnormality. 


  • 4-inch B-vent materials and venting systems should be checked to know if they are installed properly. 
  • Then, the fire pressures should be tested, and low and high fire pressures should be measured. 
  • In the end, dip switches should be inspected that are present in the circuit. Now, change the PC board and CO sensor. 

Error Code 41

This code lets you know that the freeze protection sensors have a problem. 


  • First, assess the circuit and find out broken and damaged wirings. Then, see if the sensor is enclosed with insulation or not. 

Error Code 52

This error occurs in regions with high air pressure. This error is linked with the modulating solenoid valve, or maybe the POV valve is not working well. 


  • Initially, the POV valve and the resistance readings should be assessed. If they have any problems, they should be repaired. Otherwise, the input voltage to the valve should be checked. 
  • If the error still exists, the PC board or valve should be replaced. However, before replacing them, consult with a professional.

Error Code 61

When this code appears on the appliance display screen, it indicates that there is some problem with the combustion fan motor. 


  • First of all, shut off the power and also, close the hot water fixtures. Make sure there is no air pressure. 
  • Then, test the PC board to look for broken or damaged wires or loose connections. 
  • In the next step, inspect the fan motor and remove it. By using separate power, try to run the fan motor. If the engine runs, there may be trouble with the housing. 
  • You will have to replace the fan wheel and housing in such a situation if there are no blockages. If you don’t know how to reset Rinnai tankless water heater, rely on the expert service. 

Error Code 65

This error code exhibits that the water flow servo has some problems. When this code shows up, troubleshooting Rinnai tankless water heater or hard reset should be performed. 


  • All the wiring connections on the circuit board should be assessed. Also, grab information about the water flow rate. Then, shut off the power and wait for a few moments before turning it on. Now, the code should vanish, but if it still exists, call a plumber for help.

Error Code 72

It means that the flame sensing device has some issues. It also appears when the internal temp is high and flammable. 


  • Initially, test the wiring harness from the flame rods and look for broken or loose connections. 
  • Now, assess the flame rod when the heater fires. If you see any flame, shut off the unit instantly, remove the flame rod, and then again, search for the carbon contents in the machine and clear them. 
  • Ultimately, inspect the burner to find out rust and remove it. 

Also Read: How to Flush Rinnai Tankless Water Heater

Error Code 79

Rinnai tankless water heater beeping 79 is a severe problem that should be addressed immediately. 


  • Turn off the power quickly and also keep the warm water fixtures closed. Now, test the heat exchanger and all the internal piping. If there are drops at the device’s base, they indicate that the heater has an internal issue. 
  • In such a situation, the machine should be pulled down, and the inner cabinet should be assessed to find out if it is wholly wet or not. 
  • Finally, the particular internal pipe should be changed, and the leak sensor should be dried off. All the water in the heater should be flushed out, and then the unit should be restarted.  

Error Code LC0 To LC9

These codes indicate the amount of limescale present in the tankless water heater. The higher rating shows that a higher amount of limescale exists in the device. 


  • First of all, activate all the hot water fixtures to flush out all the water stored in the machine. 
  • Then, get to know how to reset Rinnai tankless water heater bleed for resetting the appliance, and the code will be removed. 
  • However, if the error is still present, you will have to contact a professional so that he can inspect the filter for removing the limescale. 
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These days, smart tankless water heating devices are dominating commercial and residential properties. However, just like any other appliance, they are also equipped with advanced technology to encounter troubles. 
Thankfully, they have error codes to interpret them to find out the possible solutions easily. With our guide’s assistance on how to reset the Rinnai tankless water heater, things will get sorted for you. 
Well, we always recommend you to rely on professional services if you wish to have a prolonged life from your appliance. 

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