Adjusting Co2 - Bosch 520PN Applications Manual

Condensing heat exchanger unit maintenance;
▶ Shut off power. Disconnect power cord.
▶ Dismantle all inlet, outlet pipes and the condensate tube from the
condensing heat exchanger unit.
▶ Remove the condensing heat exchanger unit from the appliance by
pulling it towards you.
▶ Dismantle all parts for inspection and cleaning.
Fig. 66 Condensing heat exchanger
▶ Check the condensing heat exchanger for any obstruction.
▶ Flush the condensing heat exchanger unit with water.
▶ Check all gasket and o-rings for damage and replace if necessary.
It is important to inspect and properly replace the
gaskets and o-rings.
▶ Assemble the condensate unit and all other parts in reverse order of
disassembly.
7.5

Adjusting CO2

The CO2 can only be adjusted by a certified gas technician with a
calibrated CO2 analyzer.
CO adjustment is required in Natural Gas
2
installations where energy content is less than 900
BTU/cuft, and in installations with repeated
unresolved EA and EC errors (ref. to page 43
"Problem solving").
CAUTION:
▶ One factor that may affect CO
pressure. Please see Chapter 4.14 for the procedure
to measure gas pressure and record your findings
below:
Static Gas Pressure: " WC
P1 Operating Pressure:
C 1210 ES/ESC
levels is improper gas
2
" WC
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.
▶ Remove brass flat head screw on the exhaust collar as seen in Fig.67.
▶ 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. 67 Measuring port
▶ Press the ON/OFF button to turn ON the heater.
▶ Press and hold simultaneously buttons
seconds, until display reads P2.
Fig. 68
▶ 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
Note: When making adjustments, make sure combustion cover is
installed.
Maintenance and service | 37
until pressure is at
2
+
or and
P
2
2
6 720 644 887 (2013/02)
for 3