Navien NFB Series Installation & Operation Manual page 30

3.5.2 System Application - Zone System with Zone Valves (Primary/Secondary Piping)
Return filter
Not to exceed 4 pipe Dia or Max. 12"
System application drawings are intended to explain the system piping concept only.
Note
●
Install a filter in the system return to remove foreign objects from the system. Foreign objects inside the system may result in
●
abnormal system operation.
Refer to "3.3 Filling the System" on page 27 for make-up water connections and refer to the requirements of your local codes
●
to ensure compliance.
Use a pump with an integral check valve or install a check valve at the pump outlet.
●
Refer to "3.6.5 Wiring Diagram - Zone Valve System" on page 39 for wiring connections.
●
30 Installing the System Piping
Additional Zone
Zone Valve
(Typical)
Air Separator
Boiler Pump
Zone #2
Zone #1
System Pump
Backflow preventer
Pressure reducing valve
Expansion Tank
Make-up Water