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Most server racks have several pieces of IT equipment to power. A typical configuration can include a server, storage device, broadband switch, and routers. In a small server cabinet, you may be able to connect everything to a rack mount UPS if it has enough socket outlets btu the likelihood is that you will need to install a power distribution unit (PDU).
Power distribution units can be grouped into two types:
|Non-intelligent||Basic, Basic Monitored PDUs|
|Intelligent||Metered, Outlet Metered, Outlet Switched with Metering|
Whether to you need a non-intelligent or intelligent PDU there are crucial factors to consider.
A basic PDU is as the name suggests a power distribution unit with socket outlets and a mains power lead with a plug. The PDU should have a level of power protection in case of overload or short-circuit in the form of a fuse or circuit breaker protection. The PDU may provide for the option of a surge protection circuit to provide additional filtering to the connected loads for electro-magnetic interference (EMI) and spike or transient voltages.
A monitored PDU, is based on a basic PDU and has a built-in digital or LCD meter to show power readings for the total connected loads. Typically, the value shown is the Amps, but some devices may scroll or allow manual scrolling of other values including the voltage supplied via the socket outlets.
When buying a basic or basic monitored PDU, the choices revolve around:
When calculating how many socket outlets are needed, it is important to keep in mind the Amperage rating of the types available.
|Outlet Type||Max Amps Rating|
These ratings apply to the outlet and plug. For example, if you have 6 x C13 outlets and a 1 x C14 plug the limiting load size factor is the plug which will not be capable of drawing more than 10A. If you overload the plug, the fuse or breaker protection will activate.
Intelligent PDUs add level of sophistications to power distribution within IT server racks and include:
The most sophisticated type of intelligent PDU is the switched PDU with outlet metering. This is the most used type of PDU in a data centre environment due to the critical power monitoring and control capabilities it provides.
Automatic Transfer Switches (ATS) provide a way to automatically transfer between two power sources (A and B) to protect a critical IT load. An ATS can provide some of the functions of a PDU in terms of monitoring and control and ATS products are available rated at 10/16a and 32A. An ATS differs to a Static Transfer Switch (STS) in that the switching is relay-based with a typical power break of 4-10ms whereas a static switch has a zero-transfer time using make-before-break technology. The 4-10ms break is like that for line interactive UPS and does not typically lead to IT device issues, due to the internal capacitance (energy storage) of the power supply used.
Server Room Environments can also supply custom made power distribution units made in the UK. Custom designed PDUs tend to have a longer lead time but allow the PDU to be fully tailored for client specifications. Typical examples include multi-row horizontal PDUs with individual socket outlet branch breakers, multi-outlet mixes, left and right-hand facing sockets, outlet mix and number and PDU colour finish.
Power distribution units provide the principal point of connection to the critical power path in IT, computer, server room and data centre racks. Care should be taken to ensure the right power distribution system is installed. Whilst it is important to consider remote PDU monitoring and control, it is also important to ensure the basics are right. These include mapping out each server rack to identify all the IT load connections, their types (C13, C14, BS 1363, and hardwired) and the total power drawn (in Amps per phase, and voltage) by each device. Where an off-the-shelf PDU will not satisfy all the specification requirements, a custom-made PDU can be considered and lead times for these can be fairly quick when working with UK suppliers and manufacturers.
The number of options available when specifying server rack power distribution units is immense. One of our server rack PDU manufacturing partners has over 5,000 drawings covering permutations that have either been manufactured and delivered or at least quoted over the last decade. Such a number is possible due to the number of PDU options available which can range from outlet socket types, to cable connections, form factors, voltage, communications and even paint colours. Our rack PDU guide details a step-by-step process to help demistify their specification and help you to select the righ server rack PDUs for your comms room, server room or data centre projects.