• 550 WWhen two identical power supplies are installed, the power supply configuration is redundant (1 + 1). In redundantmode, power is supplied to the system equally from both power supplies to maximize efficiency.When only one power supply is installed, the power supply configuration is non-redundant (1 + 0). Power is supplied tothe system only by the single power supply.NOTE: If two power supplies are used, they must be of the same type and have the same maximum output power.Hot Spare FeatureYour system supports the Hot Spare feature that significantly reduces the power overhead associated with powersupply redundancy.When the Hot Spare feature is enabled, a redundant power supply is switched to a sleep state. The active power supplysupports 100% of the load, thus operating at higher efficiency. The redundant power supply in the sleep state monitorsoutput voltage of the active power supply. If the output voltage of the active power supply drops, the redundant powersupply in the sleep state returns to an active output state.The active power supply can also activate a sleeping power supply if having both power supplies active is more efficientthan having the redundant power supply in a sleep state. The power supply defaults are to wake both power supplies ifthe load on the active power supply is greater than 50% and to sleep the redundant power supply if the load falls below20%.You can configure the Hot Spare feature using the iDRAC settings. For more information on iDRAC settings, see theiDRAC7 User's Guide underSoftware → Systems Management → Dell Remote Access Controllers , at support.dell.com/manuals.Removing A Redundant Power SupplyCAUTION: Many repairs may only be done by a certified service technician. You should only performtroubleshooting and simple repairs as authorized in your product documentation, or as directed by the online ortelephone service and support team. Damage due to servicing that is not authorized by Dell is not covered by yourwarranty. Read and follow the safety instructions that came with the product.CAUTION: The system requires one power supply for normal operation. On power-redundant systems, remove andreplace only one power supply at a time in a system that is powered on.1. Disconnect the power cable from the power source.2. Disconnect the power cable from the power supply and remove the straps that bundle and secure the systemcables.NOTE: You may have to unlatch and lift the optional cable management arm if it interferes with power-supplyremoval. For information about the cable management arm, see the system’s rack documentation.3. Press the release latch and pull the power supply straight out to release it from the power distribution board andclear the chassis.78
