32 NPE Service Manual
Water
Heater
Fuel
High fire Low fire
%CO
2
%CO
2
NPE-150S
NG 8.9 9.5
LP 10.2 10.8
NPE-180A
NPE-180S
NG 8.9 9.5
LP 10.2 10.8
NPE-210A
NPE-210S
NG 8.9 9.5
LP 10.2 10.8
NPE-240A
NPE-240S
NG 8.9 9.5
LP 10.2 10.8
Table 2. CO
2
and CO value
(CO
2
values must be within 0.5% of the values listed.)
c. Fully open several hot water fixtures and set the
water heater to operate at 1-stage MIN mode (refer to
page 40). Measure the CO
2
value at low fire.
If the CO
2
value is not within 0.5% of the value listed in
Table 2, the gas valve set screw will need to be adjusted.
If adjustment is necessary, locate the set screw as shown
in Figure 8. Using a
5
/
32
in or 4 mm Allen wrench, turn
the set screw no more than
1
/
4
turn clockwise to raise or
counterclockwise to lower the CO
2
value.
Figure 8. Set Screw Location
Note
The set screw is located behind the screw-on
cover. This must be removed first.
1 2
NG
1 2
LP
1 2 3 1 2 4 5 6 7 8 9 10
ON ON
DANGER
●
When conversion is required, be sure to set the Front Panel
DIP switches according to the supply gas type.
●
Failure to properly set the DIP switches could cause carbon
monoxide poisoning, resulting in severe personal injury or
death.
10. Turn on the gas and water supply to the water heater.
11. Measure and adjust the gas/air ratio.
Option 1. Using Combustion Analyzer (recommended)
a. Loosen the screw, rotate the plate and remove the gasket
to access the emissions monitoring port as shown in
Figure 7.
b. Insert the analyzer into the port (Figure 7).
Figure 7
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