Error codes for Ultra Low Nox gas water heater
![Ultra low nox error codes](http://waterheatertimer.org/images/Ultra-Low-Nox-error-codes-8.jpg)
Inside the combustion chamber is a low nox burner.
The red and white wires from front of gas valve go down to the
combustion chamber.
Generaly the wires connect to the 'heat sensor' or chamber sensor
located on front of combustion chamber, then connect to the
thermopile located inside combustion chamber.
The thermopile is set into the pilot flame. Heat from pilot flame
causes an electric current that flows along the wires, back to the gas
valve where the current powers the circuit board located inside gas
valve.
The purpose of the sensor is to prevent overheated combustion chamber.
When heat inside combustion chamber exceeds 180-210° (or whatever the
calibration temperature is), then the sensor trips off.
If sensor trips
from overheating, then the electric current going to gas
valve is off, and gas valve issues error code 10.
If thermopile
fails, or pilot is not functioning correctly, or gas pressure is low, then gas valve issues error code 2.
If the sensor
fails, then the gas valve issues error code 9,
and the sensor needs to be replaced.
Error 4 is issued when temperature of water inside tank exceeds 180°F. Read about error code 4
Note that the error codes are not 100% ... some folks email that they
fix and fix and fix their heaters and it still doesnt work even after
replacing gas valve.