Navien NFC-250/175H Installation Manual page 43

3.6.10 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
Note
combi pre-heat and external recirculation sections in "11.5.3 Setting the DHW Operation" on page
114 for details.
Check
Valve
City
Water
Supply
* A Taco 008-BC6 or Grundfos 15-42 BUC7 (or equivalent) circulation pump is recommended for use with the NFC-H boiler and
DHW recirculation systems.
* When using the external recirculation mode, observe the following maximum recirculation pipe lengths including fittings (
pipe is recommended). Lengths 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
Note
modes can be used after installing a recirculation pump.
Recirculation
Pump
(max. 2.5A)
Check
Valve
* Recirculation Pump
Return Water
/ "
1
2
100 ft (30 m) 400 ft (120 m)
SUPPLY RETURN OUTDOOR T/S_ZONE3 T/S_ZONE2 T/S_ZONE1
TEMPERATURE SENSOR R W C R W C R
Pump Ground
DHW Supply
/ "
3
4
Installing the System Piping
lLWCO
AC24VL
AC24VN
W C
3
/ "
4
43