Navien NPN Installation & Operation Manual page 21

Navien recommends connecting the water heater as
the first water heater downstream of the gas meter,
to ensure a sufficient gas supply.
Gas meter's capacity ≥ Total gas
capacity of connected appliances
Gas Supply Line
DANGER
If the connections leak, harmful flue gas may
cause personal injury or death. After completing
the installation and filling the water heater with
water, turn on the water heater and text for leaks
using a bubble test kit. After applying the soap
solution, bubbles, will form on the connection if
any leaks exist.
20 Installing the Water Heater
The water heater is
recommended to be
the first appliance to
be connected to the
gas supply line.
To connect the gas supply:
1. Determine the gas type and pressure for the
water heater by referring to the rating plate.
2. Perform a pressure test on the main gas supply
line.
3. Purge the gas line of any debris.
4. Determine the proper size and type for the gas
line. Refer to the tables that follow.
5. Install certified full port valves on the gas supply
line and water heater.
6. Connect the gas supply line.
7. Test the supply line, all connection points, and
the water heater for gas leaks.
Gas Supply
Gas Inlet Adapter
Bottom View
Full Size
Gas Pipe
Gas Shutoff
Valve
Union