Powering the Future: Revolutionizing Data Center Design (BUS PAC)

Overview

The paper opens with survey data showing how thin high density still is in the field: in a 2022 survey only 10% of sites had racks at 20-29 kW, 7% at 30-39 kW and 3% at 40-49 kW. That small base is used to frame its argument that the jump is coming from AI and HPC loads, and that sites will have to rethink the distribution architecture rather than stretch the old one. For AI and HPC racks it cites 40-125 kW today, with extreme cases of 80-200 kW per rack.

The proposed answer is three-phase track busway rated from 40 A up to 1,250 A. The busway runs overhead along the row, racks are fed from it through tap-off boxes, and adding or moving a load means plugging into the track rather than pulling new cable runs. Inside the rack, high-amperage rack PDUs take over. The range described has inputs of 16-100 A, single-phase inputs at 100-277 V and three-phase inputs at 208, 400, 415 and 480 V.

Metering accuracy of +/-0.5% (billing grade) and environmental sensing are offered, which turns per-rack energy measurement into a product feature instead of a separate engineering job. It is a vendor paper and the comparison is framed around its own product family, so it contains no independent cost or reliability data. The standards it ties to (IEC 61439-6 for busbar trunking, UL 857, NEC 645) still give a useful frame for understanding why remote panels and whip-based distribution lose flexibility as density rises.

Key points

1. 2022 survey: only 10% of sites had 20-29 kW racks, 7% at 30-39 kW and 3% at 40-49 kW.
2. AI/HPC racks run 40-125 kW today; extreme cases reach 80-200 kW per rack.
3. Track busway is rated from 40 A to 1,250 A, three-phase.
4. Rack PDU inputs are 16-100 A; single-phase 100-277 V, three-phase 208/400/415/480 V.
5. PDU metering accuracy is +/-0.5% (billing grade).
6. Related standards: IEC 61439-6, UL 857, NEC 645.
7. Traditional 120/208 V distribution with remote power panels (RPPs) loses flexibility in dense rows.

Using it in design

• Add busway entries with 40-1,250 A ampacity and tap-off ratings to the electrical catalog; define rack PDU entries at 16-100 A and 208/415/480 V.
• For racks above 20 kW, default to three-phase 415 V (or 480 V) PDUs.
• Where a row has many racks or density changes often, suggest overhead busway instead of RPP whip distribution.
• Add a rule requiring metered PDUs with +/-0.5% accuracy on racks that must be billed per tenant.

Who should read it

Electrical designers and colocation operators choosing power distribution for high-density racks.

Related standards

• IEC 61439-6
• UL 857
• NEC 645

Publication details

Authors

Legrand

Publisher

Legrand (Server Technology)

Year

2024

Document number

V2076 R2

Document language

English

Source type

Manufacturer

Access

Free to read

Licence

Copyright retained; citation only — the publisher’s terms apply to the original document

Citation