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How to Select a PDU

Published by Lee Kelly on 07 February 2020


PDU, in a basic form, is just designed to protect and distribute power to different networking and rack equipment. If you are a small company with a couple of servers you will still need a few PDU’s and if you own a server room or data centre you may need hundreds of PDUs to populate all your racks.

With technology always changing and improving with a range of ever-changing needs, there are multiple types and styles of PDU’s available for you to choose from. With monitoring and switching of individual ports, colour coding and remote shutdown groups of ports. You need to be sure you are getting the PDU that suits your needs.

Critical Power Supplies - Easy PDU, Metered, 1U, 16A, 230V, (8)C13

Mounting Types

You need to decide how you would like to mount your PDU with a couple of options you need to see which will work best for your needs. You can install your PDU horizontally which takes up valuable rack U space. The other option is using vertical mounting where you can mount your PDUs along the side of your racks this doesn’t take up any U space and allows for you to cable manage your equipment more efficiently due to being able to have a PDU on either side of your rack. But you can mount them both on one side if that’s what you need.

Voltage

The voltage of the PDU needs to correct; otherwise, you may break some of your equipment. With voltages being 230/240V, and increasingly three-phase PDUs being 400V for power density applications in data centres.  You need to confirm your infrastructure voltage that you will be using for your racks before you select your PDU.

Amperage

Your power rating determines the amperage level you will need. Having a load that is 30A on a 16A fuse will blow a fuse. You need to be sure that your draw won’t exceed the rated draw of your PDU. With different amperage's of PDU with ranges from 16A, 30A, 60A, and potentially more depending on your use case.

Critical Power Supplies - APC Metered PDU with amps display

Single or Three-phase Power

What type of power does your equipment have access to? Single-phase or Three-phase. This will determine the kind of power distribution that you need for your setup. Single-phase setups will have the wire directly run to the rack, and it is the same for three-phase. Whichever type is brought to the rack is the type of PDU you will need.

Plug Type

The UK standard plug is BS 1363 or C14 sockets which handle up to 13A, but anything more significant than that will be using a commando plug that can handle anything bigger than 13A. Having the correct type of plug for powering you PDU is a significant consideration since it could affect your whole plan.

Power Cord Length

The standard length of power cord varies based on the manufacture of the PDU, but most of the time, this can be customised to your requirements. The standard for a majority of PDU manufactures is around 10 Feet, but this can be tailored to your needs up to any length that you require. But it is generally accepted that PDU cords shouldn’t reach more than 15 feet away from the distribution board.

PDU Connectors

The number of connectors that you need should not be based on solely the amount of devices you need to plug in now but should allow for future expansion. The number of connectors can be customised depending on your needs, and a full PDU solution can be created to your specification. The number of connectors you see in a rack PDU is often balanced per phase. This is why you see off the shelf solutions use 24, 30 and 42 because these are all divisible by 3.

The type of your connectors can be configured to your needs a most computer and rack equipment use either C13 or C19 input cables, so you need to make a decision on the ratio that you require.

Critical Power Supplies - PDU connector types C13 and C19

Local Meters

These are the options that you can choose from to enhance your ability to keep track of your PDUs. With options of having local meters, they let you know when circuits are approaching maximum capacity. When you know how much your amperage your PDU is pulling, then you can make decisions accordingly to stay on to of any issues.

Critical Power Supplies - Enlogic metered PDU

Remote Monitoring

If you are wanting to know more than just the amps being pull by your PDU and be able to see this data while your away from the racks then having remote monitoring is a must for you. With remote monitoring for your PDU, you can monitor things such as your voltage, amperage and current power being drawn per phase. With this remote monitoring, you can even go to a granular level by monitoring each socket that is on the PDU. You can also set parameters so that you can get alerts when the PDU is reaching capacity or isn’t performing correctly. An important management feature is Field population management across multiple sites in-country or globally.

Remote Switching

If you require remotely switching your PDU off at the socket level, then you will need a switched PDU this will let you control the sockets on an individual level. This will provide you with more control of your racks without having to be in the same room as them physically.

Critical Power Supplies - Eaton remote switching and monitoring software

Select the correct PDU

With the previous ten things you need to think about when selecting your PDU in mind, you can make a selection confidently know what you need. But if you need a bit more help, you can talk to our expert team on 0808 164 0608 or drop them an email here.