Metered, Monitored, Switched, Smart: Comparing Types of PDUs

Power distribution units (PDUs), commonly referred to as power strips or rack mounted power distribution units (RMPDUs), are critical components within a data center's power hierarchy. They include multiple outlets that provide power to rack level equipment and can balance the demand to prevent circuits overloading. Having the right power distribution units for your facility can help you do even more -- like remotely access critical data on power usage in real time, examine historical trends, and even remotely manage power usage.

PDUs range from “basic PDUs” to various types of “smart PDUs.” The terms describing smart PDUs are often used interchangeably, making the distinctions confusing. Let’s clarify the PDU options and how they compare.

Basic PDUs

A basic PDU essentially serves the same function as a power strip. It is a device with multiple outlets designed to distribute electric power to computers, networking devices within a rack, or other critical equipment. These types of PDUs are the easiest way to distribute power to multiple loads. A basic PDU does not collect any data from the equipment connected to it.

To collect data from this equipment, you may not need to replace the PDU -- you could simply connect it to a Smart Power Cable and make it smart (an option we’ll explore after the PDU overview).

Smart PDUs

Basic PDUs graduate to smart PDUs once they provide some degree of power usage data. A PDU’s intelligence level, if you will, depends on the data collected, whether or not that data can be accessed remotely, and if it allows some remote control of power availability. Here are the types of smart PDUs, based on their level of capability (and cost).

Metered PDU

Metered power distribution units have a built-in current meter that locally monitors load level. A metered PDU does not enable connection to a data network. The data you see on the device is what’s happening right now. There is no easy means of accumulating information unless you have a spare resource willing to stand over the device and record readings every minute. With such laborious data collection, spotting problems and avoiding downtime is not possible. However, like basic PDUs, remote monitoring capability can be easily added with a Smart Power Cable.

Monitored PDU

Graduation day: What’s the difference between a metered PDU and a monitored PDU? With monitored power distribution units you can remotely monitor voltage, power, frequency, and load levels in real-time via a built-in networking capability. You can review historical data and see trends in power usage. You can also receive general alarm notifications based on settings and thresholds you pick. This means you can immediately identify and respond to problems anywhere in your facility that has monitored PDUs.

Some monitored PDUs require hard wiring to the data network in order to provide access to the data captured (wired PDUs) while wireless PDUs don’t need data communication wiring to transmit data. Wireless remote monitoring saves time and money, especially in facilities that have a lot of PDUs. You save on the cost of the wire, the time it takes to make long wire runs, and other IT expenses needed for intricate build-outs.

Switched PDU

Post-graduate: What’s better than a networked, monitored PDU? One that helps with your power management chores. In addition to full monitoring capabilities, switched power distribution units allow key personnel to control the on/off state of individual outlets remotely. This allows operators to manage critical loads, avoid wasted power, ensure equipment is plugged in to the correct phase, and schedule downtime for power re-balancing.

Switched PDUs are desirable because they eliminate a lot of opportunities for human error, increase safety and offer effective control of power distribution. But be aware, they often come with a hefty price tag!

Making PDUs Smarter

A PDU is considered “smart” if it captures data on power usage. But if that data isn’t easily gathered or shared, how smart can that really be?

A metered PDU (and even a basic PDU) can become smarter via a Packet Power Smart Power Cable. This simple upgrade can wirelessly send the data captured by the PDU to your data network in real-time.

Packet Power Smart Power Cables are vendor agnostic – meaning they work with any existing PDUs. These cables offer many cost and functionality advantages:

• They save money compared to the cost of new intelligent hard-wired PDUs -- in device costs as well IT overhead costs like cable drops, switches, IP addresses and labor.
• They enable facilities to “get smart” quickly.
• They are quick and easy to install – literally plug and go, no electrician required. They are also self-configuring.
• They send data securely.
• They support all types of NEMA, IEC, specialized, and regional power connectors.
• You can upgrade your PDUs one at a time or transform an entire facility into a smart power grid all at once.

A monitored PDU that is not connected to your network is stranded. It’s capturing data but you can’t access it. You can take advantage of this investment by installing a Packet Power Wireless Network Connector. 

Wireless Network Connectors (WNCs) make select metered devices that aren’t currently networked, work over Packet Power’s wireless network. Plug the Wireless Network Connector into the Ethernet or serial port of the supported device. Configure the device’s network connection and data will begin to flow to the Ethernet Gateway, similar to other Packet Power wireless monitoring devices. You’ll be able to access monitoring data through your existing BMS, DCIM or Packet Power's EMX monitoring software.

Which PDU is best for you?

Basic PDUs provide additional outlets but no power usage data. Metered PDUs give you real-time data but no way to remotely access or aggregate the data. Monitored PDUs provide essential real-time and historical information allowing you to analyze trends and alert personnel to impending problems. Switched PDUs provide the capabilities of monitored PDUs with the additional benefit of remote on/off power control at the outlet level.

We can help with your PDU strategy

As you consider your PDU options, it can be easy to waste time and money with unnecessary replacements or enhancements. We can help you balance functional needs with budget constraints and ensure you're getting the most from your existing investments. Email sales@packetpower.com.