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Bosch 940 ESO Manual page 31

940 eso - natural gas / 940 eso - liquefied petroleum (lp) gas
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Static Gas Pressure:
" WC
P1 Operating Pressure:
The P1 minimum operating gas pressure is 3.5" WC for Natural Gas and
8" WC for Propane. Do not proceed in adjusting CO
or above these levels, but not to exceed 10.5" WC for Natural Gas and
13" WC for Propane.
A. Once Gas Pressure is adequate
▶ Press ON/OFF button to turn OFF the heater.
▶ To measure CO2 on this appliance, a measuring port is available
under the louvered grill on the front of the outdoor vent cap.
▶ To access measuring port, remove two screws on either side of the
louvered grill.
▶ Pull louvered grill free from vent cap.
▶ Insert CO
analyzer probe into the measuring port. The tip of the
2
probe should be in the center of the flue pipe (approx 1.5" inserted).
Avoid air gaps between probe and measuring port as they can alter
readings.
Fig. 56 Measuring port
▶ Press the ON/OFF button to turn ON the heater.
▶ Press and hold simultaneously buttons
seconds, until display reads P2.
Fig. 57
▶ Press
button until "P1" appears on display.
B. Measuring CO
(Combustion cover Installed):
2
▶ Open all hot water taps to achieve a flow rate of at least 6 gallons per
minute. (1 tub and 2 sinks should be sufficient). If heater display
reverts back to P2, open more hot water fixtures to allow sufficient
flow. Press + until P1 reappears on the display.
▶ Record the CO
reading in P1 below. (Analyzer reading may take
2
several minutes to stabilize).
▶ Press the '+' button until P2 appears. Unit will ramp down to low fire
and the water flow should decrease.
▶ Record the CO
reading in P2 below.
2
P1 CO
Reading:
% CO
2
P2 CO
Reading:
% CO
2
940 ESO
" WC
until pressure is at
2
+
,
and
for 3
P
2
2
Note: When making adjustments, make sure combustion cover is
installed.
CO
max. input
P1
6.9 % - 7.5 %
min. input
P2
2.3 % - 2.6 %
max. input
P1
8.7 % - 9.3 %
min. input
P2
2.7 % - 3.0 %
* 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
Changes in these inputs can result in different CO and CO
on the same appliance.
Table 17 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
▶ Loosen yellow painted Phillips screw (1) and cover should rotate
down (2) revealing a recessed brass slotted screw. Fig.58.
▶ Turning the slotted screw counter clockwise will raise P1 CO
and clockwise will lower P1 CO
screw will also change P2 CO
▶ After bringing the P1 CO2 readings in proper range, press the
button to enter the P2 mode. Verify CO
2. If P2 CO
level is off:
2
▶ Remove yellow painted #40 Torx cover from the front of the gas
valve. (Fig.59) A plastic #40 Torx screw will be revealed.
▶ Turning the plastic #40 Torx screw counter clockwise will lower P2
CO
levels and clockwise will raise P2 CO
2
Note: This screw adjustment is very sensitive and should be made in
small increments. It may take several minutes for readings to stabilize.
3. Verify both P1 and P2 CO
readings are within the ranges specified in
2
table17. Repeat steps 1 and 2 as necessary until CO
the specified ranges.
Final Readings
P1 CO
Reading:
% CO
2
P2 CO
Reading:
% CO
2
D. Returning to Service:
1. Return slotted screw cover to original position.
2. Reinstall Torx cover.
3. Remove CO
analyzer probe and reinstall flathead screw with gasket
2
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.
Maintenance and service | 31
Max. CO level
range (%)
(measured)
2
Nat. Gas
< 250 ppm
< 60 ppm
LP Gas
< 250 ppm
< 60 ppm
values.
2
values
2
levels. Adjustments to the slotted
2
levels.
2
readings in P2 mode.
2
levels.
2
values are within
2
2
2
6 720 644 956 (2016/05)
levels
2
+

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