Data center power distribution
Everything between the switchgear and the server. The layer that absorbs every density change and refresh cycle, and where you find out what a rack actually draws.
Everything between the switchgear and the server
Power distribution is the layer that gets designed last and changed most. Switchgear and transformers are fixed for the life of the building; what sits between them and the IT equipment has to absorb every density change, every refresh cycle and every tenant that wants something slightly different. That is why the decisions here are less about capacity and more about how cheaply the design can be modified later.
It is also where measurement happens. A facility with no branch-level metering cannot answer basic questions — what a rack actually draws, whether a circuit is near its limit, where capacity is stranded. Those answers determine how much of the installed capacity can safely be sold or used.
| Family | Typical configuration | Indicative lead time | Standards |
|---|---|---|---|
| Busway (Feeder / Plug-In)A rigid run you tap anywhere along its length. Replaces many parallel cable feeders where loads move. | 225–4,000 A Feeder or plug-in Copper or aluminium |
~16 weeks | UL 857 |
| Floor PDU / RPPSteps down and splits the feed into branch circuits for a row or zone. | 75–300 kVA PDU or RPP Basic or branch-level metering |
~20 weeks | UL 891 |
| Static Transfer SwitchesSwitches a load between two sources fast enough that equipment does not notice. | 100–1,200 A 2 / 3 / 4 pole 208V / 480V |
~22 weeks | UL 1008 |
| Rack PDUsThe last metre. Metered versions are how you find out what a rack really draws. | Metered / switched / monitored 208V / 240V / 415V 24–48 outlets |
~8 weeks | UL 60950 UL 62368 |
| Server Rack EnclosuresThe frame everything else is budgeted against — U-space, weight and depth. | 42U / 45U / 48U 19in / 23in 1,000 / 1,200 mm deep |
~10 weeks | EIA-310 |
Specifications that decide the selection
Metering granularity
Basic, per-inlet, or per-outlet. Per-outlet costs more and is the only way to attribute consumption to a specific device rather than a rack.
Distribution voltage
415V three-phase to the rack delivers 240V line-to-neutral to equipment and carries more power per conductor than 208V, which matters as density rises.
Tap-off flexibility
Plug-in busway lets a new drop be added without pulling cable or shutting anything down. That is the whole reason to pay for it over feeders.
Rack weight budget
Fully populated storage racks routinely reach the enclosure's rated capacity. Weight, not U-space, is often what runs out first.
Selection criteria in practice
- Design for change, not just for load. This layer will be modified repeatedly over the building's life. Busway and modular PDUs cost more up front and far less on every subsequent change.
- Apply the 80 % derate before counting racks. It is the difference between a plan that works and one that trips under load.
- Decide what you need to measure, before buying. Retrofitting branch-level metering is expensive; specifying it at purchase is comparatively cheap.
- Trace both paths on dual-corded equipment. A/B redundancy only holds if the two feeds are genuinely independent all the way back to their sources.
- Check enclosure depth against the deepest thing you will ever fit. Depth constrains cable management and airflow, and it is fixed once the rows are set.
Typical applications
A modern hall runs busway overhead down each row, with plug-in tap boxes dropping to rack PDUs in each cabinet. Floor PDUs or RPPs serve zones where a transformer step-down or dense branch-circuit distribution is needed. Static transfer switches feed single-corded equipment from two sources. Rack enclosures set the physical envelope everything else is budgeted against.
Work the numbers before you specify
Related reading
Common questions
Why is usable circuit capacity only 80 % of the breaker rating?
Because a circuit supplying a continuous load must be sized at 125 % of that load, which is the same constraint expressed the other way round. Data centre load is continuous, so a 20 A circuit yields 16 A usable. Planning against the nameplate figure instead is how racks end up tripping under normal operation.
Is busway worth it over cable feeders?
If loads will move or grow, generally yes. The premium buys the ability to add a tap-off without pulling new cable or de-energising anything. On a fixed layout that will never change, feeders are cheaper and perfectly adequate — but that layout is rarer than people expect.
What is the practical difference between a PDU and an RPP?
A floor PDU usually includes a transformer, stepping distribution voltage down and splitting it into branch circuits. A remote power panel distributes at the incoming voltage with no transformer. If no step-down is needed, the RPP is smaller, cheaper and produces less heat.
Do I need switched rack PDUs?
Only if you need to power-cycle individual outlets remotely. Switched units cost meaningfully more and add a failure point; monitored-but-not-switched is sufficient for most sites, which mainly want visibility rather than remote control.
Family reference pages
Each family below has its own page: how it is specified, the standards it is built to, its indicative lead time and market price band.
Specifying distribution equipment?
Every family is in the Spec Library with its configuration axes, the standards it is built to, its indicative lead time and its market price band. Take the specification to whoever supplies it — Voltfield sells nothing and is not a route to any of it.