Navien NFC-250/175H Installation Manual page 44

3.6.11 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 line and connect to the CNC6 terminal on the PCB.
(Refer to "3.7.4 Wiring Diagram - Zone Pump System with DHW Recirculation" on page 48 for details.)
CAUTION
The aquastat temperature must be set lower than the NFC-H boiler DHW set temperature.
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
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).
●
44 Installing the System Piping
Recirculation
Pump
(max. 2.5A)
SUPPLY RETURN OUTDOOR
TEMPERATURE SENSOR
Check Valve
* Recirculation Pump
Aquastat
Return Water
/ "
1
2
100 ft (30 m)
lLWCO
AC24VL
AC24VN
SUPPLY RETURN OUTDOOR T/S_ZONE3 T/S_ZONE2 T/S_ZONE1
TEMPERATURE SENSOR R W C R W C R W C
T/S_ZONE3 T/S_ZONE2 T/S_ZONE1
R C R C R C
W W W
Pump Ground
DHW Supply
/ "
3
4
400 ft (120 m)
lLWCO
AC24VL
AC24VN
2
Wired
HotButton
1
Aquastat
Wired
HotButton
Wired
HotButton
3
/ "
4