Noritz Tankless Water Heater Error Codes: Troubleshooting Guide

If your Noritz tankless water heater is displaying an error code, it's possible that you won't need to call a professional plumber. Check the error code, and if the fix is something you feel comfortable handling, you can save yourself some money by fixing it yourself.

It's important to note that your owners manual is always your best resource when it comes to troubleshooting your tankless. Even though this article covers the individual error codes for Nortiz tankless water heaters, manufacturers make changes to their product lines. For this reason, to ensure you have the most accurate information for your specific model, we always recommend checking your owners manual.

Error Codes for Nortiz Tankless Water Heaters

About Nortiz Tankless Error Codes

If there's a problem with your unit a numerical error code will begin flashing on the remote controller. When the error first appears, the display and operation light will start flashing together. Both indoor and outdoor Nortiz tankless water heaters are connected to a remote controller. 

Error codes help diagnose issues that could go unnoticed until the tankless fails. By taking appropriate action when an error code displays you'll save money when it comes to repairs and replacement costs.

Although this article will cover the majority of the error codes on your Nortiz unit, we always recommend checking your owners manual for information on your specific Nortiz model. Should you see an error code that is not listed below or in your manual, you should contact Nortiz at 866-766-7489, they can help you troubleshoot the situation and recommend next steps.

Common Nortiz Error Codes

Although you may see a variety of error codes displayed on your Nortiz tankless water heater, the most common ones you'll see are: Error Codes 11 - 12 - 16 - 29 - 73 - F76 - 90.

In some cases, you may be able to resolve the problem yourself, in others you'll need to contact a professional.

Error Code 05

Service Warning

This error code is service reminder and not an indicator that there's a failure. If you see an Error Code 05 your Noritz tankless water heater is due for maintenance. 

• Contact a professional plumber who is experienced in working with Noritz heaters to provide service to your tankless
• Failure to perform regular maintenance will reduce the service life of your unit

Error Code 10

Gas Combustion Issue

An Error Code 10 indicates an uneven output, or that the combustion continues even after the unit has shutdown

• Check the burner for foreign materials that are burning after the combustion ends. Oil, dirt, or grease are common culprits to cause an Error Code 10
• Inspect the exhaust flue for a blockage
• If the unit has a recirculation loop, you'll need to verify that you maintain a 10° water differential
• To reset an Error Code 10 you'll need to turn the unit off, then wait 60 seconds before turning it back on

Error Code 11

Ignition Failure

An Error Code 11 occurs when your tankless unit is not firing up to heat the water. The problem could be due to insufficient airflow, insufficient gas supply, or an issue with the ignition plug.

• Check that the gas valve is fully open
• Check the vent to ensure there aren't any blockages and the unit is getting good air flow
• Check the ignition rod for scale build-up. Flush the unit if needed.
• Reset the unit by powering it off and on. Then open a hot water tap. If the error code returns, you should contact a professional plumber who'll check that the pressure is within the recommended ranges, inspect the ignition rod (flame rod), and perform additional troubleshooting as needed

Error Code 12

Weak Flame

An Error Code 12 indicates that the unit has a weak flame and is not properly heating the water. 

• Check that the gas valve is fully open
• Check the vent to ensure there aren't any blockages, and that the unit is getting good air flow
• Clean the flame sensor rod and ignition plug
• Call a professional plumber

Error Code 14

Thermal Fuse

An Error Code 14 indicates the thermal fuse is faulty. This can happen if the heat exchanger is dirty or has scale build-up.

• Replace the thermal fuse. It's a white cord that wraps around the tankless water heater's heat exchanger
• Check that the unit is receiving adequate air flow for combustion, and that the burn is clean and operating properly
• Check the water quality. If the water is hard, the tankless will need to be flushed more frequently. In addition, the heat exchanger can clog if there's excessive sediment. We highly recommend purchasing a sediment filter

Error Code 16

Extremely High Water Temperature

Your Noritz unit will throw an Error Code 16 when the output temperature is far above the set temperature. As a safety measure, and to prevent scalding, the main servo will shut down the tankless when an Error Code 16 occurs.

• The most common reason for an Error Code 16 is scale build-up within the heat exchanger. Flush the tankless and then perform a hard reset by unplugging the unit for one minute before plugging it back in
• Another cause could be either low water pressure or a clogged water filter
• The problem could also be caused by high manifold gas pressure. Contact a professional plumber to adjust your manifold pressure values

Error Code 20

High Limit Switch

An Error Code 20 indicates that the high limit switch has been activated.

• Inspect the high limit switch, replace if needed
• Flush your Noritz tankless unit. The most common reason the high limit switch triggers is because of scale build-up

Pressure Switch

Your unit has experienced a pressure switch abnormality if you see an Error Code 21.

• Inspect the pressure switch, replace if needed
• Inspect that the fan motor is operating properly
• Inspect the exhaust flue for blockages

Error Code 29

Condensate Drainage Issue

This error only occurs in condensing tankless water heaters since they have a special drain line designed with a neutralizer that reduces the acidity of the outflow from the condensate. An Error Code 29 indicates there's a blockage in the condensate drain line or it's not properly routed, or the neutralizer is clogged. 

• Inspect the condensate drain for blockages
• Inspect the water level sensor for dampness or damage
• Inspect the neutralizer. It may be frozen
• Call a professional plumber

Inlet Thermistor Failure

An Error Code 31 indicates the inlet thermistor is not properly functioning.

• Replace the inlet thermistor

Error Code 32

Outlet Thermistor

If your Noritz unit displays an Error Code 32 the hot water outlet thermistor is not properly functioning.

• Inspect the outlet thermistor and replace if necessary
• Contact a professional plumber

Error Code 33

Heat Exchanger Thermistor

An Error Code 33 indicates that there's an issue with the heat exchanger thermistor.

• Check and replace the heat exchanger thermistor
• Contact a professional plumber

Error Code 45

Water Leak

An Error Code 45 indicates that excessive moisture or water has been detected within the unit.

• Shut off the cold water supply valve
• Check for water leaks or moisture
• Reset the tankless by unplugging. Wait 60 seconds and then plug it back in
• If the error code displays again, contact a professional plumber for further troubleshooting and repairs

Gas Manifold Solenoid

An Error Code 51 indicates that there's an issue with either the gas manifold solenoid or it's circuit.

• Check the solenoid valve connections for damage and proper set up
• Check that the coil's resistance is within the proper range
• If necessary, replace the gas valve, manifold plate, or the Control Board

CCP Valve 

An Error Code 56 indicates there's an abnormality with the CCP Valve. If you see this error, there are a few things you can check, but more than likely your time will be better spent hiring a professional plumber since the CCP Valve must be installed by a licensed technician.

• Check for blockages in the heater flow
• Check the CCP Valve using the system controller
• Contact a professional plumber licensed to work on Nortiz heaters to replace the CCP Valve

Error Code 59

Combustion

An Error Code 59 indicates an abnormality with the unit's combustion. It could be an insufficient gas supply, low BTU input, or another issue such as an obstructed exhaust flue.

• Inspect the exhaust flue for blockages
• Check that the unit is receiving adequate combustion air 
  • Inspect the exhaust venting for blockages
  • Inspect and clean the fan motor and burner chamber
• Check that the exhaust damper is functioning and is not stuck
• Inspect the exhaust vent and ensure there are not too many elbows or that it isn't too long
• Check that the unit is properly set for the elevation. Readjust the settings if it's installed at a high altitude location

Fan Motor

The fan motor is not properly working if you see an Error Code 61 on your Nortiz tankless water heater.

• Measure the incoming voltage to the fan motor
• Check the circuit board that controls the fan, replace if necessary
• Replace the fan motor if necessary

Error Code 63

Recirculation

An Error Code 63 only occurs on Condensing models NRCR111DV and NRCR92DV. This error code is an indication that there's an abnormality with recirculation.

• Inspect the return line filter
• Inspect the crossover valve filter

Main Flow Control Valve

There's an abnormality with the Main Flow Control Valve if you see an Error Code 65.

• Inspect the main servo for debris and/or blockage
• Check the main servo's operation
• Replace the main servo if necessary

Error Code 66

Bypass Flow Control Valve

There's a problem with your Bypass Flow Control Valve if you see an Error Code 66.

• Inspect the bypass servo valve for blockages
• Replace the bypass servo valve if needed

Air-Gas Mixer (AGM)

An Error Code 67 indicates that there's an abnormality with the AGM. From time-to-time the AGM will get stuck. If this is the problem, the solution is very simple.

• Power down the unit and wait 60 seconds before turning it back on
• If the code does not trigger again, then you can continue to use your tankless heater
• If the code reappears, check the wiring to the AGM. If everything looks good you'll need to replace the AGM 

Circuit Board

An Error Code 70 indicates that there's an issue with the circuit board.

• In most cases, you'll need to replace the circuit board
• Contact a professional plumber as this is not a repair you can do yourself

Error Code 71

Gas Valve Drive Circuit

An Error Code 71 means there's an issue with the gas valve drive circuit. It's an indication that the voltage supply is not stable. This error is often seen with units connected to battery back-ups, generators, or solar power panels.

• Check that the voltage readings are within specifications from the control board (CB) to the gas valve
• Check the electrical ground continuity 
• Install a power surge protector if you live in an area with unstable power

Error Code 72

Flame Rod Detection Circuit

An Error Code 72 indicates that the flame was detected without the proper ignition sequence.

• Check that the unit is properly grounded
• Inspect the circuit board for damage, replace if needed
• Inspect the flame detection circuit and wires for damage, replace if needed 

Circuit Board

The circuit board has a setting error if you see an Error Code 73. This can occur if a jumper connection or dip switch setting was changed while the unit was powered on.

• Power down the unit for 60 seconds
• Check that the circuit board programming and switches are set correctly
• If the error code triggers again, you'll need to contact a professional plumber to resolve the issue

Error Code F76

Multi-System Communication Error

The Error Code F76 indicates there's a communication breakdown between two quick connected heaters. A quick connect system has two NR98 (and above) tankless water heaters, one quick connect cable, and one remote control.

• Ensure that there's only one remote used. A common mistake is to install two remotes controllers. Only one is required to operate the quick connect system
• Clear the code by disconnecting the power from both tankless heaters. Wait 60 seconds and then reconnect the power

Combustion Gas

If you see any of the three Error Codes 90; 91; or 99 there's a problem with combustion. In most cases, your best choice is to contact a professional plumber to troubleshoot and fix the problem, but there are a few things you can check on your own if you feel comfortable.

• Inspect the color of the gas flame. It should be light blue with yellow tips
• Check for flue blockages 
• Check for dirt or debris on the gas burner
• Contact a professional plumber for further troubleshooting

Error Code F90

Bad Combustion

An Error Code F90 indicates that the unit is not burning properly. There's either an issue with air, gas, or venting. In most cases this error is caused by improper installation, but it could also be an environmental issue.

• Inspect the exhaust flue for blockages
• Inspect the fan motor for debris
• Inspect the vent length, bends, elbows, draft, and dip switches
• Contact a professional plumber 

Neutralizer

An Error Code 92 or 93 is a warning that the unit's neutralizer is ending the end of its service life.

• Replace the neutralizer as soon as possible
• Reset the burner timer after replacing the neutralizer

Error Code 410

Multi-System Flow Imbalance

If you see an Error Code 410 on your Nortiz tankless it could be a number of issues

• Check the heater filter
• Check blocked heater flow
• Inspect the flow sensor for debris or damage

Error Code 760

Remote Control

If your Noritz unit displays an Error Code 760 there's an issue with the remote control.

• Power down the tankless for 60 seconds
• Inspect the remote control wiring
• Ensure there's only one remote control connected to the water heater

Error Code 903

Combustion

An Error Code 903 indicates an issue with combustion or improper airflow.

• Inspect the combustion air flow. Look for blockages to the air inlet and exhaust vent
• Inspect that the fan motor is operating properly. It may be necessary to replace the control board or fan motor
• Check the vent length and altitude settings
• Check the combustion flame
• Contact a professional plumber

Error Code 941 or 942

Excessive Exhaust Temperature

If your Nortiz tankless water heater displays either an Error Code 941 or 942 it's an indication the exhaust temperature is too high.

• Look for a blockage in the combustion air supply
• Inspect the exhaust vent for a blockage
• Call a professional plumber