Navien NFC-175 Installation & Operation Manual page 34

3.6.5 System Application - Combi Pre-Heat Mode
Combi pre-heat allows NFC boilers to pre-heat to ensure a quick supply of hot water when there is no external recirculation system. This mode
is enabled by default. (Refer to the combi pre-heat section in "11.3.4 Setting the DHW Operation" on page 90 for details.)
3.6.6 System Application - External Recirculation with NaviCirc
The following pump models are recommended for use with the NFC boiler and DHW recirculation systems.
When using the indicated pump models, observe the following maximum recirculation pipe lengths:
100 feet (30 m) equivalent length of
●
400 feet (120 m) equivalent length of
●
External Recirculation Mode
For best performance, select the Intelligent or Weekly option in the External recirculation DHW recirculation menu. To use the aquastat mode,
install an aquastat to the DHW pipe lline and connect 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.)
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
Install the NaviCirc recirculation valve on the faucet furthest from the NFC boiler.
Note
●
If installed in close proximity to the boiler, faucets further down the supply line will take longer to receive hot water.
●
34 Installing the System Piping
/ " copper pipe
1
2
/ " copper pipe
3
4
Recirculation
Pump
(max. 2.5A)
* Recirculation Pump
Check
Valve
/ "
1 3
2
100 ft (30 m) 400 ft (120 m)
SUPPLY RETURN OUTDOOR
TEMPERATURE SENSOR
Pump Ground
DHW Supply
Return Water
/ "
4
lLWCO
AC24VL
AC24VN
lLWCO
AC24VL
AC24VN
SUPPLY RETURN OUTDOOR T/S_ZONE3
TEMPERATURE SENSOR R W C
T/S_ZONE3
R W C
NaviCirc
(Sold Separately)
3 / " pipe is recommended). Lengths
4