Adjusting Co2 - Bosch 940 ES Installation Manual

Maintenance and service
16.Reconnect electrical supply to unit, open water
shutoff valves, and return the unit to service.
Fig. 64
6.4 Adjusting CO
The CO can only be adjusted by a certified gas
2
technician with a calibrated CO
CO adjustment is required in Natural
2
i
Gas installations where energy content
is less than 900 BTU/cuft, and in
installations with repeated unresolved
EA and EC errors (ref. to page 46
"Problem solving").
Caution: One factor that may affect
CO levels is improper gas pressure.
2
Please see Chapter 3.14 for the
procedure to measure gas pressure
and record your findings below:
Static Gas Pressure:
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 until pressure is at or above these levels,
2
but not to exceed 10.5" WC for Natural Gas and 13"
WC for Propane.
A. Once Gas Pressure is adequate
B Press ON/OFF button to turn off the heater.
B Remove brass flat head screw on the exhaust collar
as seen in Fig. 65.
40
2
analyzer.
2
" WC
" WC
B Insert CO
analyzer probe into the measuring port.
2
The tip of the 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. 65 Measuring port
B While holding the Program (P) button in, press the
ON/OFF button to turn ON the heater (see Fig. 66).
As soon as '188' flashes on the display, release the
Program button. The display should now read P2.
Press ' ' button until "P1" appears on display.
Fig. 66
B. Measuring CO (combustion cover must be
2
installed):
B 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.
B Press '
' until P1 reappears on display.
B Record the CO
reading in P1 below. (Analyzer
2
reading may take several minutes to stabilize).
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
2
% CO
2
adjustments, make
6 720 644 930
sure