WattNode Pulse Output kWh Transducer Connection Instructions
Page 6 of 7
For best accuracy, we recommend connecting the
N
(neutral) terminal to earth ground. This is not necessary on balanced
three-phase circuits, where the ground-to-phase A, ground-to-phase B, and ground-to-phase C voltages are all roughly the
same. This will not cause ground current to flow because the neutral terminal is not used to power the WattNode.
Figure 6: Three-Phase Three-Wire Delta (No Neutral) Connection
Recommended WattNode Models
The following table shows the WattNode model that should be used, depending on the line to neutral voltage and line to line
voltage (also called phase to phase voltage).
Line to Line Voltage
WattNode Model
208 - 240 VAC
WNB-3D-240-P
480 VAC
WNB-3D-480-P
Grounded Leg
In rare cases, one of the phases may be grounded. You can check for this by using a multimeter (DMM) to measure the
voltage between each phase and ground. If you see a reading between 0 and 5 VAC, that leg is probably grounded.
The WattNode will correctly measure circuits with a grounded leg, but the measured voltage and power for the phase will be
zero and the status LED will not light for whichever phase is grounded, because the voltage is near zero. Also, one or both of
the active (non-grounded) phases may show yellow or red/yellow LED flashing because the grounded leg configuration
results in unusual power factors.
For optimum accuracy with a grounded leg, you should also connect the
N
(neutral) terminal on the WattNode to the ground
terminal; this will not cause any ground current to flow because the neutral terminal is not used to power the WattNode. If
you have a grounded leg configuration, you can save money by removing the CT for the grounded phase, since all the power
will be measured on the non-grounded phases. We recommend putting the grounded leg on the
ØC
(Phase C) input and
attaching a note to the WattNode indicating this configuration for future reference.
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