Bosch AquaStar 250SXO Manual page 27

9 Special adjustment for measuring and adjusting CO
The CO can only be adjusted by a certified gas
2
technician with a calibrated CO
Caution: One factor that may affect
CO levels is improper gas pressure.
2
Please see
procedure to measure gas pressure
and record your findings below:
Static Gas Pressure:
P1 Operating Pressure:
The P1 minimum operating pressure is 5" WC for
Natural Gas and 11"WC for Propane. Do not proceed
in adjusting CO until pressure has been verified to be
2
at or above these levels, but not to exceed 14" WC.
A. Once Pressure is good
B Turn ON/OFF switch to the OFF (O) position.
B Remove plug by prying with a small flathead
screwdriver. Fig. 35
B Insert CO
analyzer probe into the measuring port on
2
the front right of the vent cap at an angle. The tip of
the probe should be inserted to the middle of the vent
cap (approx 5" inserted).
Note: Vent cap must be in place in order to measure
CO .
2
Fig. 35
B While holding the Program (M) button, move the ON/
OFF switch to ON (I) position (see Fig. 36). As soon
as '188' flashes on the display, release the Program
button. The display should now read P2.
Fig. 36
6 720 607 440
Special adjustment for measuring and adjusting CO2 levels
analyzer.
2
Chapter 2.9 for the
" WC
" WC
B. Measuring CO (Cover Installed):
2
B Open hot water taps to achieve a flow rate of at least
4 gallons per minute. (1 tub and 2 sinks should be
sufficient).
B Record the CO
reading in P2 below. (Analyzer
2
reading may take several minutes to stabilize).
B Press the
button until P1 appears. Unit will ramp
up to high fire and the flow should increase.
B Record the CO
reading in P1 on the next page.
2
P2 CO Reading:
2
P1 CO Reading:
2
Compare your readings to those found in table 1 under
the "With Front Cover" column. If CO
make adjustments as outlined below.
Note: The "Without Front Cover" column gives
approximate values with the cover off to ease the
adjustment process. Final readings should be taken
with the cover on.
C. Adjusting CO :
2
Note: P1 adjustment will change the P2 reading.
Confirm the P1 value BEFORE adjusting the P2 level.
1. P1 CO level off:
2
B Loosen yellow painted Philips screw (1) and cover
should rotate down (2) revealing a brass slotted
screw. Fig. 37.
B Adjusting 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
2
2. P2 CO level off:
2
B Remove yellow painted #40 Torx cover from the front
of the gas valve. (Fig. 38) A plastic #40 Torx screw
will be revealed.
B Adjusting the plastic #40 Torx screw counter
clockwise will lower P2 CO
will raise P2 CO levels.
2
Note: These screw adjustment are very sensitive and
may take several minutes to stabilize.
3. Verify both P1 and P2 are within the ranges specified
in table 1 under the "With Front Cover" column. Repeat
steps 1 and 2 as necesssary until CO
the specified ranges.
levels
2
% CO
2
% CO
2
readings are off
2
levels.
levels and clockwise
2
values are within
2
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