Navien NFC-175 Installation & Operation Manual page 36

3.6.8 External Recirculation with Dedicated Return Line (Always On, Weekly, Intelligent)
External Recirculation Mode
For best performance, select the intelligent or weekly option in the external recirculation DHW recirculation menu.
Combi pre-heat is the default mode for DHW recirculation. To select external recirculation, refer to the combi pre-heat and external
Note
recirculation sections in "11.3.4 Setting the DHW Operation" on page 90 for details.
City
Water
Supply
* A Taco 008-BC6 or Grundfos 15-42 BUC7 (or equivalent) circulation pump is recommended for use with the NFC boiler and DHW recirculation systems.
* When using the external recirculation mode, observe the following maximum recirculation pipe lengths including fittings (
in excess of these limits will require a larger recirculation pump.
Maximum Equivalent Copper Pipe Lengths
Pipe Diameter
Maximum Pipe Length
If a dedicated return line is installed for external recirculation, the Always On, Weekly, and Intelligent modes can be used after
Note
installing a recirculation pump.
36 About the Boiler
Recirculation
Pump
(max. 2.5A)
Check
Valve
Check
Valve
* Recirculation Pump
Return Water
/ "
1 3
2
100 ft (30 m) 400 ft (120 m)
Pump Ground
DHW Supply
/ "
4
lLWCO
AC24VL
AC24VN
SUPPLY RETURN OUTDOOR T/S_ZONE3
TEMPERATURE SENSOR R W C
3 / " pipe is recommended). Lengths
4