Navien NCB-180 Installation & Operation Manual page 63

16. 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 Fuel
NG
NCB-180
LP
NG
NCB-210
LP
NG
NCB-240
LP
Table 2. CO
(CO values must be within 0.5% of the values listed.)
2
62 Appendixes
High fire Low fire
%CO %CO
2 2
8.9 9.5
10.2 10.8
8.9 9.5
10.2 10.8
8.9 9.5
10.2 10.8
value
2
c. Fully open several hot water fixtures and set the boiler to
operate at 1-stage MIN mode.
For operation mode selection, refer to "9.4
Note
Setting the Operation Mode" on page 51.
Measure the CO value at low fire.
2
If the CO value is not within 0.5% of the value listed in
2
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 / in or 4 mm Allen wrench, turn
5
32
the set screw no more than
counterclockwise to lower the CO
Figure 8. Set Screw Location
The set screw is located behind the screw-on
Note
cover. This must be removed first.
d. Fully open several hot water fixtures and set the boiler to
operate at 2-stage D. MAX mode (refer to "9.4 Setting the
Operation Mode" on page 51). Measure the CO
high fire.
If the CO values do not match Table 2 at high fire, do not
2
adjust the gas valve. Check for the proper Gas Orifice.
DANGER
Improper gas valve settings can cause severe personal injury,
death or substantial property damage.
/ turn clockwise to raise or
1
4
value.
2
value at
2