Bosch 715ES Service Bulletin

Service Bulletin G3-12
Models: 715ES, C800ES, C920ES, C920ESC, 2400ES, 2700ES
Measuring and adjusting CO₂
Introduction
NOTE: The CO levels can only be adjusted by a trained gas
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technician with a calibrated combustion gas analyzer. Please
note that a combustion gas analyzer is not the same equipment
as a CO detector.
Tools needed:
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
proceeding.
Preparation
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.
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Figure 1
4. Insert CO analyzer probe into the measuring port. The tip of the
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probe should be in the center of the flue pipe (approx 1.5"
inserted).
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)
Measuring CO
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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 reading below.
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P1 CO reading:
% CO
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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
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several minutes to stabilize).
P2 CO reading: % CO
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6. Compare your readings to those found in Table 1. If CO
readings are incorrect, make adjustments as outlined in the next
section.
) button, press the ON/OFF
Figure 2
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2
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