Adjusting Co2 - Bosch 940 ESO Instruction Manual

Maintenance and service
16.Reconnect electrical supply to unit, open water
shutoff valves, and return the unit to service.
Fig. 57
10.4 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 40
"Problem solving").
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 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 To measure CO
on this appliance, a measuring port
2
is available under the louvered grill on the front of the
outdoor vent cap.
34
2
analyzer.
2
Chapter 7.6 for the
" WC
" WC
B To access measuring port, remove two screws on
either side of the louvered grill.
B Pull louvered grill free from vent cap.
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.
Warning: Outdoor vent cap will get
very hot during operation.
B Ensure the vent cap is cool before
performing the procedure below.
B When measuring is complete, replace louvered grill
with screws.
Fig. 58
1 Measuring port
B While holding the Program (P) button in, press the
ON/OFF button to turn ON the heater (see Fig. 59).
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. 59
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).
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