Navien NHB-055 Installation & Operation Manual page 40

To measure the inlet gas pressure:
1. Shut off the manual gas valve on the gas supply line.
2. Turn on the boiler. On the Front Panel, press and hold the
Diagnostics Button for over 5 seconds until "1.PAR" is displayed.
3. Press the + (Up) button two times to change the display to
"3.OPR".
4. Press the Mode button once to access the Operation Mode
menu.
5. Press the + (Up) button until "MAX2" is displayed.
6. Press the Reset button twice to return to normal operation
mode.
7. Run space heating. The gas in the gas supply line will be
purged.
8. Leave the boiler on until the boiler shuts down due to a lack of
gas supply, and then turn off the boiler.
40 Connecting the Gas Supply
Opened Closed
Gas Valve
MODE O O
9. Remove the front cover by loosening the 4 Phillips head screws
securing it to the case.
10. Loosen the screws indicated in the figure below and connect a
manometer to the pressure port. Reset the manometer to zero
before use.
11. Re-open the manual gas valve and check for leaks.
12. Activate multiple zones to ramp the boiler up to its maximum
firing rate.
13. When the boiler reaches its maximum firing rate, check the
inlet gas pressure reading on the manometer. The gas pressure
must fall within the ranges specified on page 8.
Digital pressure
manometer