Noritz Tankless Error Codes: 11, 12, 16, 90 and More

Check the part that is yours

11, ignition failure. Noritz says the heater knows there is a demand for hot water but cannot ignite, usually no spark or not enough gas reaching the burner. Sometimes it lights but the flame rod fails to detect it.

12, flame loss. The flame lights but will not stay lit, so the water never reaches temperature. Noritz calls it a weak flame, caused like 11 by a lack of gas or air.

Your check: is the gas on? Noritz’s advice for 11 is to check the gas is turned on before calling a contractor. On propane, look at the tank: Noritz names an empty storage tank for 11, and a low tank for flame loss.

In winter, with everything running. Noritz says an undersized gas supply can starve the heater when several gas appliances run at once. A contractor measures that with a digital gas manometer.

What the contractor does. Noritz lists confirming the gas valve is open, the vent is clear and the ignition rod is attached and free of buildup, which it says is the most common cause of no spark.

Treat 16 and 20 as a warning

16, outlet temperature spike. Noritz says the outlet water temperature jumped abnormally high and the heater restricted its flow. Reset it by unplugging the heater for 20 seconds. Noritz lists scale, manifold gas pressure and the wrong gas type.

20, high limit switch. The switch trips as the water nears 176 to 205°F, depending on the model, and needs a power reset. Noritz says the most common cause is scale in the heat exchanger.

14, thermal fuse. Noritz says the fuse physically breaks in an extreme overheat and cannot be reset. Replacing it means taking out the heat exchanger, 2 to 4 hours of work, so Noritz recommends replacing the heat exchanger at the same time.

The lesson. Noritz warns that resetting code 20 over and over without fixing the cause is likely to end in a 14. A descaling flush, and a water softener on hard water, is what stops the climb: why scale slowly starves a tankless heater.

Work Noritz's owner checks

29: the condensate line. Noritz says the drain runs by gravity, must be plastic, at least half an inch inside, sloped all the way, with no extra trap. Run outside in a freezing area, it can freeze and back up.

71: the power. Noritz says battery backups and solar inverters must give a pure sine wave, and an old fridge or freezer on the same circuit can upset the board. Try the heater on a different circuit: what power cuts and brownouts do to heating equipment.

73: a reset. Noritz says it comes from changing a dip switch or jumper with the power on. Unplug for 30 seconds and plug back in.

94 and 903: the vent ends. Noritz says to check the air inlet and exhaust for blockage and keep the vent termination screens clear. It adds storms and hurricanes to the list of causes for 903.

760 and F76: the remote. Make sure the remote’s cord is secure all the way to the heater. With two linked heaters, Noritz says only one remote should be connected.

Know when to stop

90 on a new install. Noritz says it is more often low gas pressure, venting installed wrongly, or dip switches not set for elevation, pipe size or length. That is the installer’s job.

90 on an older heater. Noritz says it is more likely a dirty unit from missed maintenance, such as a fan full of lint. A technician cleans it.

14, and 20 that keeps coming back. The thermal fuse and heat exchanger, or scale that needs a proper flush.

91, 45 and 67. The wrong gas type, an internal leak, and the air gas mixer. All inside the heater.

11 and 12 that survive the gas check. The ignition rod first, then the high voltage cords, the igniter and the board. Noritz says to start where the spark happens and work back to the board.