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Maintenance and service
41
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. 67.
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. 68) 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 26. Repeat steps 1 and 2 as
necesssary until CO
2
values are within the specified
ranges.
4. Once CO
2
values are within the specified ranges,
verify the CO readings on P1 and P2 do not exceed
values shown in table 26. If values exceed this limit,
inspect vent system and fin coils (chapter 6.1, page 38)
for blockage.
D. Returning to Service:
1. Return slotted screw cover to original position and
tighten philips screw.
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
P2 CO
2
Reading:
% CO
2
P1 CO
2
Reading:
% CO
2
Fig. 67 Adjusting P1 CO
2
level
Fig. 68 Adjusting P2 CO
2
level
CO
2
range (%)
Max. CO
level
(measured)
Nat. Gas
max. input
P1
6.3 % - 6.9 %
< 250 ppm
min. input
P2
2.3 % - 2.6 %
< 60 ppm
LP Gas
max. input
P1
8.7 % - 9.3 %
< 250 ppm
min. input
P2
2.7 % - 3.0 %
< 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 26 CO
2
& CO target numbers
6720608158-38.1AL
