39
Installing the System Piping
3.6.5 Wiring Diagram - Zone Valve System
The NHB-H 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
R
W
C
R
W
C
Boiler Pump FUSE
(250VAC_10A)
ZONE3 Pump FUSE
(250VAC_10A)
ZONE2 Pump FUSE
(250VAC_10A)
ZONE1 Pump FUSE
(250VAC_10A)
CNP1
CNP2
CNA1
IN
OUT
N
L
CON2
CON1
R
W
C
R
W
C
CNB1
CNG1
CNF1
CNK1
CNI1
(250V 3.15A)
ZONE3
ZONE2
ZONE1
DHW
CNT1
CNT2
CNT3
CNT4
SUPPLY
RETURN
OUTDOOR
DHW
TANK
CNJ1
CND1
CNV3
CNV2
CNV1
CNC3
ZONE3
LWCO
ZONE2
ZONE1
CNC4
CNC5
CNC6
CNC1
CNC2
R
W
C
R
W
C
R
W
C
R
W
C
CNB1
CNG1
CNF1
CNK1
DHW
CNJ1
CND1
CNV3
CNV2
CNV1
CNC3
ZONE3
LWCO
ZONE2
ZONE1
CNC6
CNC2
W
C
COM
NO
NC
COM
NO
NC
COM
NO
NC
AC24VN
AC24VL
LWCO
System Pump
(max. 2.5 A)
Zone valve 3
(max. 1A)
Zone valve 2
(max. 1A)
Zone valve 1
(max. 1A)
Thermostat 3 Thermostat 2
Thermostat 1
Pump Ground
DHW Aquastat
(priority)
Live
Live
Live
Neutral
Neutral
Neutral
DHW Pump
(max. 2.5 A)
Boiler Pump
(max. 2.5 A)
Ther
mosta
t Input
Ther
mosta
t Input
Ther
mosta
t Input
24 V
AC
L
24 V
AC
L
24 V
AC
L
OUT
IN
OUT
IN
OUT
IN
Note
●
NO (Normal Open): Power is supplied when the zone valve is operating, and power turns off when
the zone valve stops.
●
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
●
The boiler has an internal 24V transformer that is rated for 75VA. This transformer provides power
to the zone valve, low water cut-off (LWCO) and thermostat terminals.
●
If the total power consumption of all 3 zone valves exceeds 72VA, an external zone valve controller
must be used.
