Navien NFC-175, Installation & Operation Manual

Page: 36 / 124

36 About the Boiler
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.
Note
Combi pre-heat is the default mode for DHW recirculation. To select external recirculation, refer to the combi pre-heat and external
recirculation sections in "11.3.4 Setting the DHW Operation" on page 90 for details.
N
A/H
DHW
PRI
L
N
L
N
L
N
L
N
L
Z3
Z2
Z1
AC24VN
AC24VL
lLWCO
R
W
C
T/S_D
WH
R
W
C
R
W
C
T/S_C
H _ZON
E1
T/S_ZON
E2
SUPPLY
TEMPERATURE SENSOR
RETURN OUTDOOR T/S_ZONE3
R W C
N
A/H
DHW
PRI
L
N
L
N
L
N
L
N
L
Z3
Z2
Z1
* Recirculation Pump
Pump Ground
DHW Supply
Return Water
City
Water
Supply
Check
Valve
Check
Valve
Recirculation
Pump
(max. 2.5A)
* 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 (
3
/
4
" pipe is recommended). Lengths
in excess of these limits will require a larger recirculation pump.
Maximum Equivalent Copper Pipe Lengths
Pipe Diameter
1
/
2
"
3
/
4
"
Maximum Pipe Length 100 ft (30 m) 400 ft (120 m)
Note
If a dedicated return line is installed for external recirculation, the Always On, Weekly, and Intelligent modes can be used after
installing a recirculation pump.