HP 10622 Best practices for HP 10000 Series and HP 10000 G2 Series Racks - Page 21

Power considerations Power is best managed within the rack by the use of a power distribution unit (PDU). Depending on the configuration, it may be necessary or desirable to use multiple PDUs to connect all devices inside the rack. Each PDU should be connected to a dedicated (unshared) branch circuit that is suitably rated for the continuous load of all the equipment connected to it. The total power load for a PDU should not exceed 80 percent of the branch circuit rating. If a PDU is not used, each piece of equipment within the rack should be connected to a dedicated branch circuit. Power redundancy High-availability Information Technology equipment such as servers and storage devices can be configured with backup or redundant power sources and power supplies in either of the following configurations: • 1+1 design: Two power supplies can be provided where either power supply is capable of sustaining the associated equipment's power demand. • N+1 design: Typically three power supplies are provided, requiring at least two to handle the equipment's power demand. If one fails, the other two remain on line with enough capacity to meet the power demand. It is important that the wiring and branch circuitry to each installation be suitably rated for the power demand of the connected equipment. Routing the power through separate branch circuits, breaker panels and PDUs is also recommended to provide additional redundancy. Non-redundant For equipment provided with a single source of power, all components should be connected 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 suitably rated device or add a second power distribution device and divide the load equally between the devices. High line voltage versus low line voltage HP recommends that rack-optimized equipment is installed for operating at high line voltage (200240V AC). 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. Benefits that support high line voltage operation of an installation are as follows: • Power supplies run more efficiently and waste less power when operating at 200--240V, thus saving electrical power. • Greater power capacity 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, an 115V 30A branch circuit can deliver 3450VA to a rack, while a 230V 30A branch can deliver 6900 VA to a rack. • Some products require 200-240V input power to operate at their full-rated capacity. • Power supplies run cooler at higher input voltages and therefore will last longer and improve overall availability. Also, because they run cooler, they produce less waste heat contributing to lower cooling costs. • Keeping input currents lower allows the use of smaller, more standardized power connections. 19