The standard Siemens P1 panelboard has some unique features that make it easier to design for an engineer, easier to reconfigure in the field for a contractor, and easier to upgrade and maintain for the owner|The P1 is the smallest panel in the Siemens lineup, with bus sizes up to 400 A|What makes it different is the split neutral design and the open ended bus, in the Siemens panel, instead of the common single neutral bus on one end, we have a neutral bus on both sides that is cross bussed|This makes branch wiring simpler and cleaner - the lead lengths for line and neutral can now be made nearly the same, creating more room and a neater installation|It also allows access to both ends of the bus as a standard feature - this provides the flexibility to make changes in the field, even if it wasn't part of the original configuration