Navien NFC-175 Installation & Operation Manual page 61

When PCB DIP switch 2 #8 is set to On, ensure that
Note
●
CPVC, polypropylene, or stainless steel is used for
exhaust venting.
This unit may be installed at elevations up to 10,100
●
ft (3,078 m) for use with natural gas and propane. To
use the unit at a specific altitude, the DIP switches
should be set as described above.
High Altitude: Above 2,000 ft (610 m), the unit will
●
de-rate by 3% for each 1,000 ft (305 m) of altitude
gain.
For NG, if you install the unit at above 5,400 ft (1,646
●
m), it is required to change the Gas Orifice for high
altitude. Be careful not to confuse it with the LP Gas
Orifice. Refer to "12.1 Gas & High Altitude Conversion"
on page 103 for details.
Common vent installations for use with natural gas
●
and propane are only approved for up to 4,500 ft.
CAUTION
Ensure that the High Altitude setting reflects the actual
location of the boiler. If not, it may cause personal injury or
malfunction of the boiler.
Setting the DIP Switches 61