Start with the electrical fit
Choosing the Right Rack PDU Power Distribution Unit
A rack power distribution unit might seem like a straightforward commodity, but selecting the wrong one can compromise your entire data centre infrastructure. The decision requires careful consideration of two critical factors: your rack’s total power draw and the level of visibility and control you need at each outlet.
A quality rack PDU delivers power from your data centre circuit directly to server equipment while providing essential outlet-level monitoring and switching capabilities. Modern units offer features like real-time power metering, remote outlet control, and detailed analytics—transforming a basic power strip into an intelligent infrastructure management tool that prevents downtime and optimizes resource allocation.
A rack power distribution unit looks like a commodity until you buy the wrong one. The choice comes down to two questions. How much power does the rack draw, and how much do you need to see and switch at each outlet? Answer both and the right unit picks itself.
What is a rack PDU? A power distribution unit is a strip of outlets that feeds power from a data centre circuit to the equipment in a rack. The tiers differ by how much they let you measure and control: from bare outlets, to per-outlet metering, to remote switching of individual sockets.
Start with the electrical fit
Before any feature, the unit has to match the rack it feeds. That is the kVA rating and phase, single-phase for a standard rack, three-phase Wye or Delta for high density. It is the inlet and plug type, the number and mix of C13 and C19 outlets, and the form factor, 0U vertical down the side of the rack or 1U horizontal. Get this wrong and no amount of monitoring saves you.
Then choose the intelligence tier
Once the electrical fit is right, the second decision is how much visibility and control you need. The tiers stack, each one adding the capability of the rung below.
A basic PDU gives you outlets and nothing else. Input metering adds a single current reading per circuit, enough to keep a rack under its breaker and balance load across phases. Outlet metering measures each device, which is what you need to cross-charge power or plan capacity by the socket. Switched units add remote on, off, and reboot per outlet, the answer for a site with no one on the floor. An intelligent PDU is the top rung: outlet metering and switching in one unit.
A five-line spec sheet
- Load: kVA rating and phase. Single-phase for standard racks, three-phase Wye or Delta for high density.
- Outlets: count and mix of C13 and C19, plus inlet and plug type. Locking outlets if cables get knocked.
- Visibility: input metering for basic capacity, outlet metering for per-device billing and planning.
- Control: switched outlets for remote reboot and lights-out or remote sites.
- Accuracy: billing-grade metering certified to ISO/IEC 62053-21 if you cross-charge power to tenants.
Where the Raritan PX4 lands
The PX4 sits at the intelligent tier: per-outlet metering and per-outlet switching in one unit. Its Universal Input option takes single-phase and three-phase Delta or Wye cords on the same PDU, so one model covers several rack layouts. Metering is billing-grade, accurate to plus or minus 0.5 percent and certified to ISO/IEC 62053-21, measured at the inlet and every outlet for voltage, current, active power, apparent power, energy, and power factor.
Most buyers over-spec the load and under-spec the visibility, or the reverse. Fix the electrical fit first, then buy exactly the tier of metering and control the rack needs. No more, no less.
Not sure which tier fits your racks?
Match a PDU tier to your rackFrequently asked questions
What is a rack PDU?
A rack power distribution unit is a strip of outlets that feeds power from a data centre circuit to the equipment in a rack. Beyond distributing power, it can meter consumption and switch outlets on or off, depending on its tier.
What are the tiers of rack PDU?
Five tiers, rising in capability: basic gives outlets only with no data; input-metered adds one current reading per circuit; outlet-metered measures each outlet; switched adds remote on, off, and reboot per outlet; and intelligent combines outlet metering with switching in one unit.
What is the difference between a metered and a switched PDU?
A metered PDU reports how much power is being drawn, at the circuit or the outlet. A switched PDU adds control, letting you turn individual outlets on, off, or reboot them remotely. A switched PDU with outlet metering does both.
Do I need single-phase or three-phase power?
Single-phase suits standard racks up to roughly 7 to 10 kW. Three-phase, in Wye or Delta configuration, delivers more power per cable and balances load, which is why high-density and GPU racks use it.
What metering accuracy do I need for billing?
To cross-charge power to tenants or departments, the metering should be billing-grade and certified to ISO/IEC 62053-21. The Raritan PX4 is accurate to plus or minus 0.5 percent at the inlet and every outlet.
Which PDU tier does the Raritan PX4 belong to?
The PX4 is an intelligent PDU. It combines per-outlet metering with per-outlet switching, and its Universal Input option accepts single-phase and three-phase Delta or Wye cords on the same unit.
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eNOVA Technologies is Singapore's specialist distributor for data centre IT management solutions, representing Adder, Guntermann & Drunck, Raritan, Sunbird, ZPE Systems, and VuWall across Singapore and Southeast Asia. Our technical content is produced with AI assistance and reviewed by our in-house team before publication.
This article was produced with AI assistance and reviewed by the eNOVA Technologies team. All technical claims are verified against manufacturer documentation.
