Noritz Tankless Hot Water Heater Codes 11 And 12 [Why + How To Fix]

The Noritz tankless hot water heater codes 11 and 12 represent ignition failure and flame loss. Though these two error codes don’t look different on the surface, they occur due to the same causes in most cases.

That’s why we’ve combined these two codes and created this guide so that you can easily diagnose and fix these codes. Here are the main reasons why these codes come up:

Noritz tankless hot water heater codes 11 and 12
  • Insufficient Gas Supply
  • Improper Inlet Gas Pressure
  • Malfunctioning ignition rod
  • Inadequate airflow

Now, let’s look at how we can fix them in detail.

Noritz Tankless Hot Water Heater Codes 11 And 12 [Why + How To Fix]

In this part, we will walk you through every step so that you can fix those issues regarding codes 11 and 12 from your Noritz tankless water heater. So, get started right here.

noritz tankless hot water heater

Note: You can also read how to fix Noritz tankless water heater problems & error codes.

1. Insufficient Gas Supply

Insufficient gas supply is the number one reason for displaying error code 11 as well as 12 on your Noritz water heater’s remote screen. Like every gas-fired unit, the Noritz water heater requires proper gas flow to the burner for proper combustion.

Without a sufficient gas supply, your unit won’t burn properly. Plus, your heater’s burner won’t receive enough gas if gas supply lines get clogged or blocked. For instance, dirt and debris, insects, rust, as well as physical pipe deformation may be a culprit behind the issue.

How To Fix:

First things first, you have to make sure that the main gas supply is turned on. So, check the gas valve. It should be completely parallel to the gas lines. If the valve wasn’t already in a fully open position, you need to fix it right away.

The gas valve should look like this:

inspect the gas valve

If not keeping the gas supply on wasn’t the main culprit, look for debris in the gas lines. Leaving a clogged gas line may cause a risk that may lead to a very hazardous situation.

So, remove dirt and debris from your gas control line or gas orifice. Sometimes, you may even have to install the gas lines. After cleaning or installing the gas lines completely, follow the below tips:

  • Set your gas meter as per the user manual.
  • Make sure that you’re using the right type of gas.
  • Fuel it up properly and use a proper gas regulator so that it can provide all BTUs for the unit.

2. Improper Inlet Gas Pressure

A lack of inlet gas pressure is the next leading factor that throws the problematic codes on your Noritz tankless unit. Because your heater won’t ignite if there is no proper gas pressure in the unit. 

Actually, the inlet gas pressure of a properly functioning tankless water heater should be as the following chart:

Input BTUs Of UnitType Of Unit  Recommended Gas Pressure

Over 199k
Natural Gas Operated UnitShould be between 5” to10. 5 WC to 10.5” to 14 WC
U to 199kPropane Operated Unit4” to 10.5” WC 8” to 13.5” WC

You have to measure the gas pressure in your heater to know if there are any issues with it. To measure the gas pressure, you will need the following tools. For example;

  1. A Phillips head screwdriver
  2. A digital manometer

In this procedure, you will get two types of gas pressure; one is Static and another is Dynamic pressure. Let’s complete the following steps to test the gas inlet gas pressure.

  • Turn off the gas valve.
  • Remove the screw from the inlet test port using the Phillip Head screwdriver.
  • Attach the digital monometer’s hose to the inlet port
  • Turn on the gas valve to open fully.

Now, you will see that the static gas pressure is displayed on your manometer. And this static pressure hints at the pressure with no gas operation and the gas isn’t used yet.

check out noritz inlet gas pressure

Next, in order to check the Dynamic Gas Pressure you should open some hot water fixtures. You should perform this test during gas usage. Now, test it with the manometer attachment as you did for checking the static gas pressure.

Note: The Static and Dynamic testing pressure should stay above the minimum requirements of the unit. (Zero result isn’t acceptable)

If the inlet gas pressure is going lower than the value you see on the chart, your heater won’t ignite properly. Now you know why you’re seeing the error code but you need to dig deeper and find out the main issues that have led to this issue in the first place.

Here are the most common things that lead to getting insufficient gas pressure in your water heater:

  • Improperly sized gas meter.
  • Gas supply lines of the wrong size.
  • Bad gas regulator.
  • Interrupted gas supply from the gas utility company

How To Fix:

Gas supply issues from your local utility provider can also cause this issue. So, give them a call and make sure everything is okay from their end. If there are no issues there, continue diagnosing.

If your gas meter or gas lines aren’t of the right size as suggested in the owner’s manual, you need to take corrective actions immediately. Replace the gas lines or the gas meter to make sure they match the size recommended for your heater.

In case of a damaged gas regulator or if it doesn’t function properly, we recommend you replace it. You can take help from an expert to change the gas regulator for your unit.

3. Malfunctioning Ignition Rod

When gas supply isn’t an issue, we suspect there is a problem with the ignition rod behind showing the error code.

malfunctioning noritz tankless water heater ignition plug 

The ignition rod plays the key role of igniting the heater. Over time, it gets dirty or filthy getting carbon deposits. And, then it causes the code to flash.

How To Fix:

In order to get smooth sparking on the ignition rod, you must clean it. To fix the flame issue, first, try cleaning the rods. Follow these steps to clean the ignition rod:

  • Switch Off the power supply of your heater
  • Remove the access front cover to locate it.
  • Inspect any corroded and discolored parts of the flame rods.
  • Detach the white connectors attached to the flame rods and ignitor plug.

Now, take an adjustable Phillip screwdriver to loosen the screws on the side of the unit. Remove the screw and carefully pull out the parts so that the gasket may not damage as the gasket is very fragile.

pull out the noritz tankless heater gasket

Next, pull out the ignitor. Clean the ignition rod with a fine 100-grit sandpaper as you see in the below image. And ensure there is no carbon deposition on the parts.

clean the flame sensor rod

Now, once cleaned, place it accordingly and connect the wires properly as you disconnected. Don’t forget to check out the ignition by opening or running hot water faucets. Also, inspect the burner chamber window if there is a flame. It should look like this:

noritz tankless water heater burner chamber window

Finally, if the cleaning attempt doesn’t bring any good luck, replacing the igniter will be the best solution to the problem.

4. Insufficient Air Flow

Insufficient airflow also prevents your unit from igniting properly. When your Noritz heater’s air supply is exhausted or the venting system doesn’t go properly, it causes low flame.

So, if the unit detects a weak flame, the burner won’t get sufficient air to light up. And then, it will result in poor combustion. As a result, you see the faulty code 12 on the remote display.

Mostly, your heater may suffer from sufficient airflow if the burner gets clogged by building-up large particles of dirt, dust, lint, and unexpected objects. Gradually, they prevent the fresh air supply to the burner chamber.

Besides, clogged air screen filters or exhaust vent systems are another cause for insufficient air supply. Because of the pointed reasons, you’re facing the following troubles with your heater.

  • Yellow flames
  • Unstable flame
  • Exposure to carbon monoxide

As a result, when the exhaust gets blocked, the burner suffers from lacking air for full combustion. Consequently, it will run hotter than usual.

How To Fix:

Begin your inspection with the exhaust pipe open. Next, check out the vent leading inside and outside are free from any blockage. If you can identify any obstruction, apply a vent cleaning tool to release the blockage. While doing this, don’t forget to verify any holes in the pipes.

But in case of a dirty air filter, we highly suggest you inspect the air filter screen, burner assembly, and exhaust vent. If you find any dust and lint stuck on there, clear out them completely so that there is an adequate air supply to the unit.

 And then, inspect whether the venting system has been installed correctly. Because any material can lead to blockage if it is installed too close to other objects.

Finally, keep checking if the unit is receiving sufficient air flow for proper combustion and if the burner is working properly. Hopefully, your heater will get sufficient airflow for burning properly and you won’t face the error code further.


Why does the Noritz tankless unit need a fresh air supply?

Noritz gas-operated tankless unit needs a fresh air supply to let the burner chamber work and supply enough fuel in the unit for proper combustion.

When does Noritz demand a reset procedure?

When the other solution tips can’t resolve the problem by any means, resetting the system will help you to fix most problems with your heater. After resetting, your unit will run as usual.

How Do I easily reset the Noritz error code?

When you can’t remove the code manually, you can simply reset your Noritz tankless unit. To reset, just unplug it, wait for 30 seconds, and plug it back into the power outlet. Hope the code will be cleared from the screen.

Final Thoughts

We’ve discussed how what causes Noritz tankless water heater codes 11 and 12 along with their fixes. Your unit won’t fire up to heat the water if it doesn’t get sufficient gas supply and can’t sense the flame.

We bet the troubleshooting guide will help you to erase the faulty code 11/12 from your Noritz water hot heater display. Therefore, just find the root reasons by following this guide and resolve those issues to run your unit functionally.

Yet, if you have additional queries, share your comments with us. We will respond to you ASAP.

About Phillip

Phillip is an HVAC guy & has convenient skills in the fireplace, heater, stove & other heating systems. He has been working and writing in this field for the last 5 years. He is really passionate about writing & share his expertise through his writing to help others. More about us.

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