How to Choose IT Rack Power Distribution

Overview

The paper splits rPDU selection into five steps: outlet type and quantity, power estimate, voltage, phase and breaker choice, monitoring level, and physical fit. With typically 100-700 rPDU models on the market, a structured process is a practical way to narrow the choice. C13/C19 outlet mixes and combination outlets are covered in the first step; an example is a combination rPDU with 36 C13 and 6 C19 outlets.

Temperature is often overlooked: standard C13/C19 connectors are rated for 70°C, which hot aisles can exceed. On power, the paper contrasts North American 80%-derated circuits (a 20 A circuit loaded to 16 A) with European 16 A breakers that are 100%-rated. It also notes that rack densities for AI training can exceed 100 kW. Applied together, these steps keep outlet type, circuit breaker and monitoring decisions for the same rack from contradicting one another.

On monitoring, the text explains the limits of metering accuracy: metered rPDU current accuracy is typically about ±3% across most of the operating range. Where there is no upstream branch-circuit monitoring, metered or switched rPDUs are recommended. This gives operations a practical basis for seeing actual rack loads. A limit is that the paper is a selection guide rather than a design procedure, so manufacturer and model details need separate verification. Even so, the steps help keep outlet, breaker and monitoring decisions consistent, particularly where density is rising quickly.

Key points

1. rPDUs are loaded to a maximum of 80% of rating in North America (20 A becomes 16 A); European 16 A breakers are 100%-rated.
2. Metered rPDU current accuracy is typically about ±3% across most of the operating range.
3. Standard C13/C19 connectors are rated 70°C, which hot aisles can exceed.
4. Rack densities for AI training can exceed 100 kW.
5. Example combination rPDU: 36 x C13 + 6 x C19.
6. The typical vendor range is 100-700 rPDU models.

Using it in design

• Build an rPDU selector: from rack kW, voltage, phases and redundancy, compute PDU count with an 80% (NA) or 100% (IEC) factor.
• Recommend the outlet mix from the device list by C13 and C19 counts.
• Default the monitoring level to metered.
• Flag hot-aisle-rated PDUs (60°C or higher) where containment is used.

Who should read it

Design engineers and operations teams selecting rack-level power distribution.

Related standards

• IEC 60320
• UL 60950/62368
• NEC Article 645

Publication details

Authors

Patrick Donovan

Publisher

Schneider Electric

Year

2024

Document number

WP 202

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