A rack power distribution unit (rPDU) is a device placed in server racks that is designed to distribute electrical power to server equipment. Server racks, in turn, are installed in data centers (DCs).
In most data centers rPDUs are connected to an upstream power distribution node, which can be a power distribution box connected to a busbar or a distribution panel – a data hall PDU.
rPDUs can also provide power management capabilities for the server equipment, making them an indispensable component of modern data center infrastructure.
With rPDUs it is possible to monitor power supply parameters, track energy consumption and manage the power usage of server equipment. Remote access to rPDUs can be organized through a local network.
Data centers select rPDUs based on the characteristics of the server equipment housed in the server rack. Factors such as the power capacity of the server rack, the required number of outlets and the ability of the rPDU to operate under high-temperature conditions are taken into account.
Choosing an rPDU
To properly select rPDU the following key questions should be answered:
- Type of power supply: is it single-phase with a nominal current rating of 32A or three-phase with nominal current ratings of 16A or 32A?
The total power of all equipment installed in the server rack should not exceed the nominal power rating of the rPDU. The power consumed by each device connected to the rPDU should be specified in the user manual or on the server equipment itself.
- Colocation of the rPDU in the rack cabinet: vertical or horizontal?
Depending on the mounting type rPDUs can be installed horizontally or vertically, either inside or outside the server rack casing. Horizontal rPDUs are typically installed inside the rack and usually occupy space from 1 to 4U (units), featuring 8-16 outlets. Vertically mounted rPDUs can contain up to 54 outlets. They are installed at the back or side of the rack casing, thus not occupying critical mounting space for equipment inside the rack.
- Number and Type of output outlets?
Typically selected based on the number of input outlets of the connected server equipment, but it’s wise to consider future expansion possibilities when replacing equipment. Each rPDU can support multiple types of output outlets. Each outlet corresponds to its own current and voltage rating, mainly IEC 60320 C13 (max 10A) and IEC 60320 C19 (max 16A).
- Availability of power monitoring and management.
Manufacturers categorize rPDUs for data centers into several types, with three main categories being distinguished:
Basic: provide only power distribution functionality, equipped with short-circuit and overload protection. These are entry-level solutions with low cost.
With monitoring capability: provide a comprehensive view of the power consumption of connected server equipment both locally within the server rack and via remote access, while still ensuring reliable energy distribution for the IT equipment. Such rPDUs are available in configurations for remote monitoring at the group (block) outlet level or at the individual outlet level. They provide quick access to critical information for assessing energy consumption trends as well as the ability to set user-defined alerts for power excess and the capability to send data to monitoring systems.
With management capabilities: they provide a comprehensive view of power supply parameters, both locally in the server rack and remotely, with the ability to remotely turn on, turn off or reboot the power for a group (block) of outlets or for each individual outlet. This type of rPDU is ideal for customers, who need to limit power consumption on specific outlets to avoid accidental overloads as well as for remotely rebooting equipment based on specified power parameters.
IXcellerate practice
In IXcellerate data centers the rpd BNH B800.M3x32-36 C13-6 C19 model is predominantly used. These are three-phase rPDUs with remote monitoring capabilities, featuring a nominal current rating of 32A and a maximum power consumption of 22 kW. They are equipped with 36 IEC 60320 C13 outlets and 6 IEC 60320 C19 outlets. Additionally, single-phase PDUs BNH are also utilized at the IXcellerate Northern campus.These models feature a display to show key power metrics: voltage, current and power. With remote access to the rPDU, monitoring capabilities are significantly enhanced due to the wide range of functions available through the web interface or via the SSH network protocol.
The selected rPDU allow data transmission to monitoring systems, enabling the configuration of alerts for both consumption statistics and incidents. This includes scenarios such as power loss on one of the inputs or exceeding power consumption on a group (block) of outlets.
The monitoring module records all events occurring with the rPDU and each group (block) of outlets individually, allowing precise control over the power processes happening within the server rack.