Navien NFC-250/175H Installation Manual page 85

If Recirculation Return Line Is Not Installed
Install a NaviCirc valve at the furthest fixture from the water heaters as illustrated below and set the internal
2-way valve on the 1st NPE "A2" unit to the "Ext" position. Refer to the NaviCirc and NPE-A2 Installation Manuals
for additional details. The NFC-H boiler should be set to Combi Pre-heat Mode.
Pressure
Relief
Valve
Heating
Supply
Pump
Air Separator with
Expansion Tank
Optional System
Temperature Sensors
Heating Return
Note
A HotButton and Aquastat cannot be used for cascade systems.
<NPE-A2>
Hydronic
Feed
Water Expansion
Tank
Pressure
Relief Valve
NaviClean
Domestic Hot Water Supply
<NPE-S2>
Sub1 Sub2
<NPE-S2>
Sub3
Ball
Valve
Check
Valve
Faucet
Installing a Cascade System
Domestic
Cold Water
Supply
85