Service Bulletin G3-12
Models: 715ES, C800ES, C920ES, C920ESC, 2400ES, 2700ES
Measuring and adjusting CO₂
NOTE: The CO
levels can only be adjusted by a trained gas
technician with a calibrated combustion gas analyzer. Please
note that a combustion gas analyzer is not the same equipment
as a CO detector.
Combustion gas analyzer
Flat head screw driver
Phillips head screw driver
#40 Torx driver
Measure gas pressure
One factor that will affect CO
Please see bulletin G3-02 for the procedure to measure gas
pressure. Correct any deficiencies in gas pressure before
1. Open several hot water taps and let the water heater run for 1-2
minutes. Close hot water taps and return to heater.
2. Push the ON/OFF button to the OFF (O) position.
3. Remove brass flat head screw with gasket on the exhaust collar
to reveal measuring port. (Fig. 1)
levels is improper gas pressure.
4. Insert CO
analyzer probe into the measuring port. The tip of the
probe should be in the center of the flue pipe (approx 1.5"
5. While pressing the Program (
switch to ON (I) position. As soon as '188' flashes on the dis-
play, release the program button. The display should now read
P2. (Fig. 2)
. (Fig. 2)
1. Open enough hot water taps to achieve a flow rate of at least 6
gallons per minute. (1 tub and 2 sinks should be sufficient)
2. Press the (
) button until P1 appears.
3. Record the P1 CO
4. Press the (
) button until P2 appears. Unit will ramp down to
low fire and the water flow should decrease.
5. Record the P2 CO
reading below (Analyzer reading may take
several minutes to stabilize).
6. Compare your readings to those found in Table 1. If CO
readings are incorrect, make adjustments as outlined in the next
) button, press the ON/OFF