HP BL260c HP BladeSystem c-Class Site Planning Guide - Page 34

• N+N design: N power supplies can be provided where N/2 power supplies are capable of sustaining the associated equipment's power demand. For the c7000 enclosure, this quantity is typically a 2+2 or 3+3 power supply configuration. • N+1 design: Typically four power supplies are provided, requiring at least three to handle the equipment's power demand. If one fails, the other three remain on line with enough capacity to meet the power demand. Be sure that the wiring and branch circuitry to each installation is suitably rated for the power demand of the connected equipment. To provide additional redundancy, HP recommends routing the power through separate branch circuits, breaker panels, and PDUs. Non-redundant power For equipment supplied by a single source of power, connect all components to the same power distribution device (PDU or UPS). The power distribution device should be suitably rated for the connected load. If the total load exceeds the rating of the power distribution device, obtain a suitable rated device or add a second power distribution device and divide the load equally between the devices. Line voltage selection All HP products that are optimized for rack mounting have wide-range power supply inputs designed to operate at a voltage range of 100-240V. HP recommends operating rack-optimized equipment with high line voltage (200-240V AC). Benefits of high line voltage operation include the following: • Power supplies run more efficiently and waste less power when operating at 200-240V, thus saving electrical power. • Greater capacity is available in a single rack. For the same size circuit, almost twice the power can be delivered to a rack at high line versus low line. For example, a 115V 30A branch circuit can deliver 2760VA (de-rated) to a rack, while a 208V 30A branch can deliver 4992VA (de-rated) to a rack. • Some products require 200-240V input power to operate at their full-rated capacity. • The HP 2400W High Efficiency Power Supply operates only at 200-240V AC and provides significantly higher efficiency than the 2250W power supply. • Power supplies run cooler at higher input voltages, last longer, and improve overall availability. Also, because they run cooler, they produce less heat which helps to lower cooling costs. • Keeping input currents lower allows the use of smaller, more standardized power connections. Distribution hardware This section describes wire selection and the types of raceways (electrical conduits) used in the distribution system. Wire selection Use copper conductors instead of aluminum, because aluminum's coefficient of expansion differs significantly from that of other metals used in power hardware. Because of this difference, aluminum conductors can cause connector hardware to work loose, overheat, and fail. Power requirements and considerations 34