14 Installation
Three-Phase Three-Wire Delta Without Neutral
This is typically seen in manufacturing and industrial environments. There is no neutral wire, just
three power lines with AC waveforms shifted 120° between the successive phases. With this
configuration, the line voltage wires may be connected to the
Ø
A
,
Ø
B
,
and
Ø
C
terminals in any
order,
so long as the CTs are connected to matching phases
. For these models, the meter is
powered from the
Ø
A
and
Ø
B
(phase A and phase B) terminals. Note: all delta WattNode models
provide a neutral connection
N
, which allows delta WattNode models to measure both wye and
delta configurations.
For best accuracy, we recommend connecting the
N
(neutral) terminal to earth ground. This will
not cause ground current to flow because the neutral terminal is not used to power the meter.
Figure 6: Three-Phase Three-Wire Delta Connection
Recommended WattNode Models
The following table shows the WattNode models that should be used, depending on the line-to-
line voltage (also called phase-to-phase voltage).
Line-to-Line Voltage
WattNode Model
208 - 240 Vac
WNC-3D-240-MB
400 Vac
WNC-3D-400-MB
480 Vac
WNC-3D-480-MB
Three-Phase Four-Wire Delta (Wild Leg)
The uncommon four-wire delta electrical service is a three-phase delta service with a center-tap
on one of the transformer windings to create a neutral for single-phase loads.
See
http://www.ccontrolsys.com/w/Four_Wire_Delta_Circuits
for details.
Grounded Leg Service
In rare cases with delta services or single-phase two-wire services without neutral, one of the
phases may be grounded. You can check for this by using a multimeter (DMM) to measure the
Ground
W
HI
TE
B
L
AC
K
Ø
B CT
Ø
C CT
Ø
A CT
Ø
B
Ø
C
N
Ø
A
Common
B+, D1, RxD+/TxD+
E
IA-
4
8
5
PC or Logger
A−, D0, RxD−/TxD−
Continental Control Systems LLC
Status
Status
Status
X
C
B+
A-
M
O
D
B
U
S
Com
WNC
-
WNC
-
W
ATT
N
ODE
®
M
ODBUS
-
MB
-
MB
Phase A
Phase B
Phase C
WHITE
BLACK
W
HI
TE
B
L
AC
K
LI
N
E
LO
A
D
Source
Faces
Current
Transformers
3D
-
xxx
