2.9 Power and cooling 2.9.1 PDU-based configurations The z15 power and cooling system is a change from previous systems because the system is  packaged in an industry standard 19-inch form factor for all the internal system elements. The  configuration can be 1 - 4 frames (racks). Consider the following points: The IBM Z systems operate with redundant power infrastructure. The z15 is designed with a  new power infrastructure that is based on intelligent (PDUs that are mounted vertically on the  rear side of the 19-inch racks and Power Supply Units for the internal components. The PDU  configuration supports radiator-cooled systems only. The PDUs are controlled by using an Ethernet port and support the following input: The power supply units convert the AC power to DC power that is used as input for the Points  of Load (POLs) in the CPC drawer and the PCIe+ I/O drawers. The power requirements depend on the number of CPC drawers (1 - 5), number of PCIe I/O  drawers (0 - 12) and I/O features that are installed in the PCIe I/O drawers. PDUs are installed and serviced from the rear of the frame. Unused power ports should never  be used by any external device. GLYPH<SM590000> The power subsystem is based on the following offerings: – Power Distribution Units (PDUs) that are mounted at the rear of the system in pairs  – Bulk Power Assembly (BPA), as with previous systems GLYPH<SM590000> The system uses 3-phase power: – Low voltage 4 wire “Delta” – High voltage 5 wire “Wye” GLYPH<SM590000> No EPO (emergency power off) switch is used. GLYPH<SM590000> No DC input feature is available. GLYPH<SM590000> The air-cooled z15 server now has a radiator unit (RU) N+2 design for the pumps and  blowers. GLYPH<SM590000> The water-cooled system option for the z15 server is only available with BPA-based  systems.  GLYPH<SM590000> No Top Exit Power feature is available because the 19-inch frame is capable of top or  bottom exit of power. All line cords are 4.26 meters (14 feet). Combined with the Top Exit  I/O Cabling feature, more options are available when you are planning your computer  room cabling. GLYPH<SM590000> The new PSCN structure uses industry standard Ethernet switches (up to four) that  replace the previous IBM System Control Hubs (SCHs).  GLYPH<SM590000> 3-phase 200 - 240 V AC (wired as “Delta”) GLYPH<SM590000> 3-phase 380 - 415 V AC (wired as “Wye”) z15 has a support element task to simulate the EPO function (only used when necessary  to do a System Reset Function). 76  IBM z15 (8561) Technical Guide