The ØA, ØB, and ØC voltage connections on a WattNode meter are used for two things: measuring the line voltage, which is needed to calculate energy, and to supply a few watts of power to operate the meter.
The “3D” and “3Y” characters in WattNode meter part numbers indicate how the meter gets its operating power. The “D” refers to a delta type electric service and the “Y” refers to a wye type of electric service. Either style of meter can measure 1, 2, or 3 phases depending on the number of current transformers (CTs) that are used. Either style of meter can measure delta or wye loads. The key difference between delta and wye style meters is how they are powered.
Delta (3D) meters are powered from the ØA and ØB line voltage connections. A neutral connection is not required, but the safety ground must be connected because it is used as the meter’s voltage measurement reference point. Delta model WattNode meters can be installed at any location where there are two phase conductors present. Delta meters must be used for four wire delta or grounded delta services. Additional information on these types of services is available from the Four Wire Delta Circuits and the Three-Phase Grounded Delta Circuits pages on our website.
Wye (3Y) meters are powered from the ØA phase and neutral line voltage connections. A safety ground connection is not required because the meter’s voltage measurements are referenced to the neutral connection. Wye model WattNode meters can be installed at any location where there is one phase conductor and neutral present. The phase conductor can be any of the three phases in the electrical system. Wye meters must be used for single phase (120, 230, 277, and 347 volt) applications, when the meter is installed near the load and only one phase voltage and neutral are available.
Note that the ØA, ØB, and ØC phase voltage inputs are arbitrary labels. Unlike a three phase motor where phase rotation is important, the voltage inputs to a WattNode meter can be connected to any phase voltage, in any sequence. Remember that your CTs must be installed on the same phase conductor as the voltage input for that channel (ØA, ØB, or ØC).
Because the power supply in a wye meter operates at a lower voltage than a delta meter, wye meters cost about $30 less than delta models. If you are not sure that there is a neutral present at the location where the meter will be installed, order a delta model.
For a listing of the minimum and maximum power supply voltages for all WattNode meter models, see the Operating Voltage Ranges page on our website. For information on the different types of utility services, see the Electrical Service Types and Voltages page.