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34
Maintenance and service
B While holding the Program (P) button, press the ON/
OFF button to turn ON the heater (see Fig. 62). 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. 62
B. Measuring CO
2
(Combustion cover 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.
Press + until P1 reappears on the display.
B Record the CO
2
reading in P1 below. (Analyzer
reading may take several minutes to stabilize).
B Press the ‘+’ button until P2 appears. Unit will ramp
down to low fire and the water flow should decrease.
B Record the CO
2
reading in P2 below.
P1 CO
2
Reading: % CO
2
P2 CO
2
Reading: % CO
2
Note: When making adjustments, make sure
combustion cover is installed.
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
2
level is off:
B Loosen yellow painted philips screw (1) and cover
should rotate down (2) revealing a recessed brass
slotted screw. Fig. 63.
B Turning the slotted screw counter clockwise will
raise P1 CO
2
levels and clockwise will lower P1
CO
2
levels. Adjustments to the slotted screw will
also change P2 CO
2
levels.
B After bringing the P1 CO
2
readings in proper range,
press the button to enter the P2 mode. Verify
CO
2
readings in P2 mode.
2. If P2 CO
2
level is off:
B Remove yellow painted #40 Torx cover from the front
of the gas valve. (Fig. 64) A plastic #40 Torx screw
will be revealed.
B Turning the plastic #40 Torx screw counter
clockwise will lower P2 CO
2
levels and clockwise
will raise P2 CO
2
levels.
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
2
readings are within the
ranges specified in table 15. Repeat steps 1 and 2 as
necesssary until CO
2
values are within the specified
ranges.
P1 CO
2
Reading: % CO
2
P2 CO
2
Reading: % CO
2
D. Returning to Service:
1. Return slotted screw cover to original position.
2. Reinstall Torx cover.
3. Remove CO
2
analyzer probe and reinstall flathead
screw with gasket 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.
Final Readings
Fig. 63 Adjusting P1 CO
2
level
CO
2
range (%) Max. CO level
(measured)
Nat. Gas
max. input P1 7.8 % - 8.4 % < 290 ppm
min. input P2 1.5 % - 1.8 % < 60 ppm
LP Gas
max. input P1 9.5 % - 10.1 % < 290 ppm
min. input P2 1.7 % - 2.0 % < 60 ppm
* 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
2
values. Changes in these inputs can result in
different CO and CO
2
values on the same appliance.
Table 15 CO
2
& CO target numbers
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