Bosch 940 ESO Installation Manual page 34

Maintenance and service
B Press the ' ' button until P2 appears. Unit will
ramp down to low fire and the flow should decrease.
B Record the CO reading in P1 and P2 below.
2
P2 CO Reading:
2
P1 CO Reading:
2
Note: When making
combustion cover is installed.
CO
max. input P1
min. input P2
max. input P1
min. input P2
* Values above are for climate controlled conditions.
Inputs such as gas pressure, heating value of the gas,
humidity and temperature of combustion air all impact CO
and CO values. Changes in these inputs can result in
2
different CO and CO values on the same appliance.
2
Table 7 CO & CO target numbers
2
C. Adjusting CO :
2
Note: P1 adjustment will change the P2 reading.
Confirm the P1 value BEFORE adjusting the P2 level.
1. If P1 CO level is off:
2
B Loosen yellow painted Phillips screw (1) and cover
should rotate down (2) revealing a recessed brass
slotted screw. Fig. 58.
B Turning the slotted screw counter clockwise will
raise P1 CO levels and clockwise will lower P1
2
CO levels. Adjustments to the slotted screw will
2
also change P2 CO levels.
2
B After bringing the P1 CO
press the ' ' button to enter the P2 mode. Verify
CO readings in P2 mode.
2
2. If P2 CO level is off:
2
B Remove yellow painted #40 Torx cover from the front
of the gas valve. (Fig. 59) A plastic #40 Torx screw
will be revealed.
B Turning the plastic #40 Torx screw counter
clockwise will lower P2 CO
will raise P2 CO levels.
2
Note: This screw adjustment is very sensitive and
should be made in small increments. It may take several
minutes for readings to stabilize.
34
% CO
2
% CO
2
adjustments, make
Max. CO
range (%)
level
2
(measured)
Nat. Gas
7.5 % - 8.1 % < 250 ppm
2.3 % - 2.6 % < 60 ppm
LP Gas
8.7 % - 9.3 % < 250 ppm
2.7 % - 3.0 % < 60 ppm
readings in proper range,
2
levels and clockwise
2
3. Verify both P1 and P2 CO
ranges specified in table 7. Repeat steps 1 and 2 as
necesssary until CO
ranges.
4. Once CO
2
verify the CO readings on P1 and P2 do not exceed
values shown in table 7. If values exceed this limit,
inspect vent system and fin coils (chapter 9.1, page 31)
sure
for blockage.
D. Returning to Service:
1. Return slotted screw cover to original position and
tighten Phillips screw.
2. Reinstall Torx cover.
3. Remove CO
screw with gasket in exhaust collar.
4. Press ON/OFF button to turn OFF the heater and
then turn ON the heater.
5. Heater is ready for normal operation.
Final Readings
P2 CO Reading:
2
P1 CO Reading:
2
Fig. 58 Adjusting P1 CO
Fig. 59 Adjusting P2 CO
readings are within the
2
values are within the specified
2
values are within the specified ranges,
analyzer probe and reinstall flathead
2
% CO
2
% CO
2
level
2
6720608158-38.1AL
level
2
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