This document describes the significance of the “3D” and “3Y” characters in WattNode meter part numbers. 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.