What Causes Noritz Error Code 90 and What the Possible Solutions

Don’t be alarmed when you see Noritz error code 90 flashed on your remote control’s screen. Error codes 90, 91, or 99 are basically the same: they show you that your unit is struggling with a combustion issue. Although the issue may seem serious, it’s not overly serious or risky, but you shouldn’t do anything dangerous with the unit.

If you have doubts about performing the check on your own (especially if you completely have no idea what to do with your unit), you should ask for help from a professional. NEVER try to tweak the unit on your own.

Noritz Error Code 90

Your Manual and Error Code Meaning

You can see the error code because all Noritz units are connected to remote control with an LCD screen. When the unit is running well, you won’t see anything. But when there is an issue, then you will see the code.

Noritz Tankless Error Code 90

If you consult Noritz tankless water heater manual, there are some error codes listed there. These are the most common error codes that may happen to the unit. Be advised, though, that you may not find some of the error codes on your manual. No need to worry; you can always check online. You can even find the Noritz error code list through online research.

In general, the error code 90 is related to combustion. You can check for improper gas-burning or airflow obstruction. Then you can confirm the correct gas pressure as well as the proper fuel/air mixture. If you have fixed it, you can reset the heater.

Noritz Tankless Water Heater Error Code 90

As it was mentioned before, Noritz error code 90 is about general combustion abnormality. But some people have contacted Noritz tech support, and they found out that code 90 can also be about airflow or exhaust error.

Here’s what to do if you see the error code:

  • Check the gas pressure. Each unit has its own minimum flow rate (for incoming gas). If there is not enough gas, you may suffer from restriction or obstruction in the unit.
  • Check the airflow. This is basically a ventilation problem resulting from dust, lint, or debris build-up. It obstructs or chokes the cool airflow (toward the unit), so the unit is overheating. To deal with it, you may want to try removing the front side panel. Blow the intake slots and holes out. If you have a small and portable vacuum, you can try using it. You should see a system board covered by a (black) dust shield when you open the cover. You can try removing it, but if you aren’t sure about it, contact a pro and ask for help instead. You don’t want to disassemble something, but you can’t reassemble it back again, do you?
  • Check the exhaust. If the exhaust is the issue, then no wonder you get the error code. 2 main reasons can cause exhaust issues: Your exhaust ducting is obstructed, or you use too small (diameter) for the duct to exhaust your heater. Another reason is that the flapper valve (on the system’s outlet) is somewhat stuck closed.  

How to Reset Noritz Tankless Water Heater

Resetting the unit is a complete no-brainer. But it would help if you did it as your last resort if the previous methods don’t work well. You only need to find the Reset button and press it.

You can find it on the front panel. If you have done the reset solution and the issue still isn’t resolved completely, then you should call a licensed professional or an authorized technician.

Those are the facts related to the code error, including the possible reasons and the possible solutions. At least, now you won’t be panicky anymore when you get Noritz error code 90 on your remote.