Navien NFC-250/200H User's Information Manual page 16

4. Remove the screw that secures the air intake
filter (the filter is located at the top left of the
boiler).
5. Pull the filter out of the boiler.
16 Maintaining the Boiler
6. Remove the filter from the plastic assembly.
Dust and rinse it with clean running water.
7. Allow the filter to dry completely.
8. Place the filter assembly back into the boiler and
secure it with the screw.
9. Replace the front cover.
10. Reconnect the power supply to the boiler.
11. Press the Power button (
to turn on the boiler.
) on the front panel