Navien NaviCirc Installation And Operation Manual page 25

The following diagram shows the external recirculation flow for
pre-heating:
Primary Heat Exchanger
Buffer
Secondary Heat Exchanger
Tank
Flow
Sensor
2-Way
Circulation Pump
Valve
Closed
Check Valve
Water
Adjustment
Valve
Domestic
Hot
Water
Recirculation
Water
Supply
Water Supply
Supply
[External Recirculation Mode using the Recirculation Inlet]
25