Navien NFC-175 Service Manual page 29

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 6.
b. Insert the analyzer into the port (Figure 6).
Figure 6. Insert the Analyzer
Version 1.0
The DIP SW 1 on the circuit board configures the operation status
and model/capacity settings.
O
N
1 2 3 4 5 6
Switch Function Setting
Normal Operation
2-stage MAX
Operation
1 & 2
Status
1-stage MIN
1-stage MAX
3 & 4 Reserved -
NFC-200
5 & 6 Model
NFC-175
Model Altitude
0-5,399 ft
NFC-175
NFC-200
5,400-10,100 ft
Table 2. CO
(CO values must be within 0.5% of the values listed.)
2
O
N
1 2 3 4 5 6 7 8
1-OFF, 2-OFF
1-ON, 2-OFF
1-OFF, 2-ON
1-ON, 2-ON
-
5-OFF, 6-OFF
5-ON, 6-OFF
High fire Low fire
Fuel
%CO %CO
2
NG 8.9 9.5
LP 10.2 10.8
NG 8.5 9.5
LP 10.2 10.8
value
2
NFC Service Manual
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