Navien NFB-175 Mode D'emploi page 39

3.6.5 Wiring Diagram - Zone Valve System
The NFB Boilers can operate a heating system with up to 3 zones. The following is the wiring diagram for a zone valve system with 3 zones.
Without 24VAC connections
Boiler pump
(max. 2.5 A)
DHW pump
(max. 2.5 A)
System pump
(max. 2.5 A)
NO (Normal Open): Power is supplied when the zone valve is operating, and power turns off when the zone valve stops.
Note
●
NC (Normal Close): Power is supplied when the zone valve stops, and power turns off when the zone valve is operating.
●
COM: 24 V AC COMMON
●
Pump Ground
SUPPLY RETURN OUTDOOR
SUPPLY RETURN OUTDOOR
NC
NC NC
NC
NC
COM
NC
COM
NC
NC
NO
NC
COM
NC
COM
NC
NC
NC
COM
COM
NC
NO
NC
NC
COM
COM
NC
NC
NC
NC
COM
NO
COM
NC
LWCO
COM
LWCO
COM
AC24VL
LWCO
AC24VL
AC24VN LWCO
AC24VL
AC24VN
AC24VN
NC
AC24VL
NO
COM
NC
NO
COM
NC
NO
COM
AC24VN
LWCO
AC24VL
AC24VN
C
C
W
R
C
W
R
C
W
W
R
C
C
W
SUPPLY RETURN OUTDOOR DHW TANK
R
R
W
C
R
W
R C
C
W
W
R
R
C
C
W
W
DHW TANK
R
R
C
W
DHW TANK
R
Zone
valve 1
(max. 0.75 A)
Zone
valve 2
(max. 0.75 A)
Zone
valve 3
(max. 0.75 A)
DHW Aquastat
(priority)
Thermostat Input
24 VAC L
Thermostat 1
Thermostat Input
24 VAC L
Thermostat 2
Thermostat Input
24 VAC L
Thermostat 3
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