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Troubleshooting Noritz Tankless Error Code EC12: Flame Loss


Error code 12 on a Noritz tankless water heater indicates a flame loss, meaning the flame is extinguished during operation. Troubleshooting steps include cleaning the flame rod, ensuring proper venting, and checking gas pressure.
Noritz Tankless Error Code 12: Flame Loss

An error code 12 indicates a flame loss. This means that the unit is detecting a flame, but the flame is being extinguished during operation (weak flame).


Most of the same troubleshooting used in the Error Code 11article can be applied to the Noritz tankless error code 12 such as cleaning the flame rod and making sure the unit has sufficient gas to ignite and stay lit. Additionally improper venting could be a cause especially if the unit is Direct Vented (DV) and the air intake is drawing in the exhaust of the unit or another gas burning appliance.


Specific to our Direct Vent Concentric (DVC) models, if the incorrect type of vent is used you will get 12 codes, combustion noises and other issues. Concentric venting is a pipe within a pipe style and it’s used to provide the ease of installing like a Single Vent (SV) unit with just one penetration through the building but providing the benefits of a DV install.


NR83DVC and NR98DVC models require the use of Noritz Concentric Venting. There are o-rings on the smaller 3″ exhaust venting meant to keep the seal 100% air tight and prevent it from leaking exhaust into the air intake side. If those o-rings are missing or damaged the unit could give 12 codes or other noises.


Inlet gas pressure could be an issue. When testing inlet gas pressures we recommend 3 different tests:


  1. Static Test. This is the inlet gas pressure at the unit when no gas is being used.

  2. Dynamic Test. This is the inlet gas pressure at the unit when it’s fired up and heating water.

  3. Max Dynamic Test. This is the inlet gas pressure at the unit when it’s fired up with a high demand and other gas appliances are used (furnace, oven, etc).


Under all 3 tests the inlet gas pressure to the unit should always be above the minimum required gas pressure as stated on the unit.


If the inlet gas pressure drops below the minimum rating of the unit, there is an issue in the gas supply that needs to be addressed for the unit to work properly under all conditions.


For California installations there is likely an earthquake safety shut off on the gas line near the meter that may have been tripped during an earthquake or other bump or vibration. Follow the proper reset procedure based on the shut off you have, it’s usually labelled on the device itself.


Troubleshooting gas issues should be left to a professional as there is some serious risk if you’re unfamiliar with what you’re doing.


If you are experiencing the Noritz error code 12, you may take the following actions:


  • Contact Amor Plumbing:  Reach out to Amor Plumbing for professional assistance to diagnose and resolve the issue effectively. We service all customer in the following counties: If you are in Santa Clara, Alameda County, Contra Costa, and San Mateo County.


  • You can reach Amor Plumbing in the following ways:

    • Online Contact Form: Submit your inquiry through our online contact form

    • Phone Call: Give us a call at (408) 649-3129

    • Text Message: Send a text to (408) 649-3129 include your Noritz model, serial number and a photo of your installation for faster assistance.

  • Use the Noritz Contractor Locator: Visit the Noritz website to use their contractor locator tool to find a certified technician or plumber near you to better se


If you are uncertain about the coverage of your Noritz tankless water heater, contact Noritz Technical Service at 866-766-7489.


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