Navien NHB Series Installation & Operation Manual page 67

System Application #2- Cascade System with Hydro Separator
Supply
Sub2
Main Sub1
Return
Temperature
sensors (required)
Dirt collector
Cold water
Hydro/Air separator
Back flow preventor
Expansion tank
Connect the "SH Demand (SH T/T or Zone controller)" to the main unit.
Note
Connect the universal temperature sensors to SUPPLY and RETURN terminals of the CNT1/CNT2 terminal strip on the main unit
PCB.
Connect the outdoor sensor (optional) to the main unit.
Depending on the installation environment, the supply top and return top piping option can be applied.
Installing a Cascade System 67