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44
Maintenance and service
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 Phillips screw (1) and cover
should rotate down (2) revealing a recessed brass
slotted screw. Fig. 70.
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. 71) 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 24. Repeat steps 1 and 2 as
necesssary until CO
2
values are within the specified
ranges.
Final Readings
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.
Fig. 70 Adjusting P1 CO
2
level
Fig. 71 Adjusting P2 CO
2
level
CO
2
range (%) Max. CO level
(measured)
Nat. Gas
max. input P1 7.2 % - 7.8 % < 250 ppm
min. input P2 1.5 % - 1.8 % < 60 ppm
LP Gas
max. input P1 8.8 % - 9.4 % < 250 ppm
min. input P2 1.9 % - 2.2 % < 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 24 CO
2
& CO target numbers
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