Navien NFC-175 Installation & Operation Manual page 37

3.6.9 External Recirculation with HotButton and Dedicated Return Line (HotButton, Aquastat)
External Recirculation Mode
To use the aquastat mode, install an aquastat to the DHW pipe lline and connnect to the CNC6 terminal on the PCB. (Refer to "3.7.4 Wiring
Diagram - Zone Pump System with DHW Recirculation" on page 41 for details.)
CAUTION
The aquastat temperature must be set lower than the NFC boiler hot water temperature.
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.
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 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
To use HotButton mode, install a HotButton and recirculation pump, but not an aquastat (➊).
Note
●
To use Aquastat mode, install an aquastat and recirculation pump, but not a HotButton (➋).
●
Recirculation
Pump
(max. 2.5A)
SUPPLY
Check Valve
* Recirculation Pump
Aquastat
Return Water
/ "
1 3
2
100 ft (30 m) 400 ft (120 m)
lLWCO
AC24VL
AC24VN
SUPPLY RETURN OUTDOOR T/S_ZONE3
TEMPERATURE SENSOR R W C
RETURN OUTDOOR T/S_ZONE3
R
TEMPERATURE SENSOR W
Pump Ground
DHW Supply
/ "
4
lLWCO
AC24VL
AC24VN
1
Aquastat
C
3
/ " pipe is recommended). Lengths
4
2
Wired
HotButton
Wired
HotButton
Wired
HotButton
About the Boiler 37