Navien NHB Series Installation & Operation Manual page 114

12. 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. Insert the Analyzer
Model Altitude
0-5,399 ft
NFB-
301C
5,400-
10,100 ft
Model Altitude
0-5,399 ft
NFB-
399C
5,400-
10,100 ft
Table 2. CO
(CO values must be within 0.5% of the values listed.)
2
114 Appendixes
High fire Low fire
Fuel
%CO
%CO
2
NG 9.2
LP 10.8
NG 8.8
LP 9.9
High fire Low fire
Fuel
%CO %CO
2
NG 9.4
LP 10.6
NG 8.8
LP 9.9
value
2
c. Activate multiple zones and set the boiler to operate at
1Step MIN mode.
Note
Measure the CO
If the CO
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 an Allen or Star Wrench, turn the
set screw no more than
counterclockwise to lower the CO
Note
d. Activate multiple zones and set the boiler to operate at
2Step MAX mode (refer to "11.6.7 Setting the Operation
Modes" on page 108). Measure the CO
2
If the CO
8.9
adjust the gas valve. Check for the proper Gas Orifice.
10.7
9.0
DANGER
11.0
Improper gas valve settings can cause severe personal injury,
death or substantial property damage.
2
8.9
10.4
9.0
11.0
For operation mode selection, refer to "11.6.7
Setting the Operation Modes" on page 108.
value at low fire.
2
value is not within 0.5% of the value listed in
2
1
/ turn clockwise to raise or
4
value.
2
<NFB-301C>
Figure 8. Set Screw Location
The set screw is located behind the screw-on
cover. This must be removed first.
values do not match Table 2 at high fire, do not
2
<NFB-399C>
value at high fire.
2