Today, there are several questions to consider before selecting rack PDUs that will work well for your data center application. This list below will help steer you in the right direction, ensuring that the PDUs you choose will fit the design of your data center today and in the future.
Rdekono Product Page
Depending on where you want to install it, a rack PDU can be mounted horizontally or vertically. Installed horizontally inside the rack (taking up RU space) is one option; another option is to vertically mount a PDU on the back or side of the enclosure (not taking up any RU space). You’ll often see one vertically mounted PDU on the left side and one on the right side of a data center cabinet (although rack PDUs can be mounted on either side, based on preferences).
PDUs can be mounted so that power cords exit either at the bottom or top of the enclosure. (If your data center is on a slab, for example, the power cord needs to exit at the top of the enclosure because there is no raised floor for it to pass through.)
Your power rating – the amount of sustained power draw a PDU can handle – determines the amperage level you’ll need. Why is this important? Because, for example, a PDU with a 30A fuse will blow if a 30A circuit experiences more than 30A of power for an extended period of time.
Per the National Electrical Code, 30A PDUs or higher are required to be equipped with a 20A breaker to prevent injury in the event of a short circuit.
In addition to different amperages, there are different input voltage options for rack PDUs as well; 208/240V is the most common voltage output to computing gear, with a new trend moving toward 400V input. Confirm your infrastructure voltage, and you’ll know what type of voltage you need in your PDU.
What type of input power do you have access to: single-phase power or 3-phase power? The type of power distribution in your data center will determine whether you need a single- or 3-phase PDU.
The difference involves where in the distribution system the phase is broken down. When it’s broken down at the distribution panel, power to the rack will be single-phase service (requiring single-phase rack PDUs). When all three phases are brought to each rack, then a 3-phase PDU is needed. In most data centers, the input power is 3-phase service.
Here in North America, you’ll most often see NEMA-style plugs (locking) on rack PDUs. Locking plugs are popular to secure electrical connections and prevent accidental disconnection. The other option is an IEC-style plug. A third plug type, known as the California-style plug, is sometimes seen in North American data centers as well (normally used for 50A circuits). PDUs with this plug type can also be found.
6. Power cord length
Standard power cord lengths vary based on the manufacturer, but this can often be a customizable option. Belden’s standard, for example – and the standard from most manufacturers – is 10 feet, but we’ve created rack PDUs with power cords of up to 40 feet or longer when needed. The length of your power cord is determined, of course, by how far it needs to reach to connect.
To limit power loss, it’s important to keep connection points to the DC distribution system as close to the cabinet as possible. UL limits the length of the power cord to 15 feet; longer cords may call for a rack PDU to be equipped with a terminal block and cord that is installed onsite by an electrician.
Want more information on Networking Rack Manufacturer? Feel free to contact us.
The number of receptacles you need shouldn’t be based solely on the number of devices there are to plug in right now – it should also take future rack growth into account. Although customized options are available when it comes to receptacle count, it typically makes the most financial sense to choose from a standard option. Because they can be longer, vertically mounted PDUs tend to offer more receptacles per unit.
The number of receptacles in a rack PDU is often balanced per phase (which is why you see 24-, 30- and 42-count receptacles – they’re all divisible by three for 3-phase power).
It’s also important to determine the types of plugs being used on the devices in your rack. Most computing gear use C-13 or C-19 input cords, for example, so it’s important to determine the needed ratio in your rack PDU.
PDUs with a local meter display are standard-grade rack PDUs. They indicate when circuits are approaching maximum capacity and breakers may trip. When you know how much amperage is being pulled from the PDU, you can make decisions accordingly and stay on top of potential problems.
If you want to know more than just the amperage being pulled from your PDU – and want to know that data without having to look at the PDU – a device with remote-monitoring capabilities may be what you need. It will include the voltage, amperage and power being drawn. (In a 3-phase rack PDU, you’ll see the power draw for each of the three phases.) Rack PDUs can remotely monitor at the aggregate level, phase/circuit level or outlet level. Depending on the options you select, this can help support granular power usage effectiveness (PUE) reporting. It can also help calculate individual customer power usage for billing, if needed.
Based on parameters you set, the monitoring system can even send alerts when the PDU is reaching circuit capacity or isn’t performing correctly.
If the option to remotely switch receptacles on and off is important to you, remote switching is available on some rack PDUs. This provides data center managers with better control: individual outlets can be remotely turned on and off, and gear reboots can be managed remotely.
After thinking about these 10 criteria, you should have a good idea about what features and options you need from a rack PDU. If you can’t find a standard PDU that matches what you need, Belden can customize a solution – like it has for data centers all over the world. Learn more about our customized data center infrastructure solutions.
Want to improve this post? Provide detailed answers to this question, including citations and an explanation of why your answer is correct. Answers without enough detail may be edited or deleted.
I'm looking to purchase a rack/enclosure for some servers. As this is my first time shopping for this type of equipment, I need to know what to look for. I'm asking not only about how to buy the rack, but also what accessories will I need? What can I do without? What should I look for in terms of delivery and assembly? What do I need to prepare for in terms of power? Cooling inside the cabinet? Anything else I might be overlooking?
I'll share some back story in case anyone finds it helpful, but really generic answers for anyone who is shopping for rack equipment is helpful.
Where I'm at we used to have mainly tower servers... even a number of glorified desktops that lived in our server room. We do have a couple two-poster racks for switches, but everything sits in a wooden bench made of 2x4's and plywood that's been here much longer than I have. Over the last three years I've been able to virtualize the desktop "servers" and as items have come up for refresh I've purchased rackmount servers, with rails. I put the servers on their sides in the old space, and set the rails aside in the store room, biding my time.
We are now (at last!) to the point where in the next six months I'll be down to only a single tower server, and it just happens to be 19 inches high, so I'm thinking 1U shelf. Everything else except the the UPS equipment should mount in a rack. In anticipation of that event, I'm looking to spec out a server rack enclosure to purchase and install this summer. I want to be get preliminary shopping done over the next month or two so I can get it put into the budget for next fiscal year, in time to actually execute the project late this summer.
For size, we should fit comfortably inside a single 42U height-wise, even including mounting our existing switches, so I'm pretty sure one rack will handle it. ... I just need to know what to look for in that rack.
If you want to learn more, please visit our website custom rack mount enclosures.