Navien NFC-175 Installation & Operation Manual page 32

3.6.3 System Application - Zone System with Pumps (Primary/Secondary Piping)
Not to exceed 4 pipe Dia or Max. 12"
Pressure
Relief Valve
System application drawings are intended to explain the system piping concept only.
Note
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Install a NaviClean filter in the system return to remove foreign objects from the system. Foreign objects inside the system may
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result in abnormal system operation.
Refer to "3.4 Filling the System" on page 28 for make-up water connections and refer to the requirements of your local codes
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to ensure compliance.
Use a pump with an integral check valve or install a check valve at the pump outlet.
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Refer to "3.7.3 Wiring Diagram - Zone Pump System" on page 39 for wiring connections.
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32 Installing the System Piping
NaviClean
Air Vent
Additional Zone
Zone #2
Air Separator
Expansion Tank
Zone #1
Backflow
preventer
Pressure
reducing valve
Make-up Water