Data Center Projects: Establishing a Floor Plan

Overview

The reasoning is that density, phasing and criticality are specified per row, so the floor plan has to be settled before detailed design. Rows are laid out as hot-aisle/cold-aisle pairs on a 2 ft (600 mm) tile grid. As a rough estimate, rack locations equal room area divided by 28 sq ft (2.6 m2) per rack. Four standard pitches, measured mid-cold-aisle to mid-cold-aisle, are defined: A compact 7 tiles/14 ft (4 ft cold, 3 ft hot); B wide cold aisle 16 ft (6 ft cold, 3 ft hot); C wide hot aisle 16 ft (4 ft cold, 5 ft hot); D wide hot and cold 18 ft (6 ft cold, 5 ft hot).

Pitch B provides 50% more raised-floor cooling capacity in the cold aisle for higher-density raised-floor designs; pitches C and D suit racks with rear cooling accessories. On hard floors the pitch can be compressed provided aisles stay at least 3 ft (hot) and 4 ft (cold); 50 in deep racks, for example, give a minimum pitch of 15 ft 4 in. Row ends need at least 2 tiles of clearance to plain walls (3 preferred in large rooms), rows over 10 racks may need breaks by local regulation, and rows of 1-3 racks should be avoided.

The paper shows how columns and partitions can remove whole rows. In a 40-rack-location room with no column, a column in an aisle that forces rows to shift drops the count to 29, a loss of over 25%, while rotating the layout axis 90 degrees keeps 35. A misplaced partition lost 10 of 80 racks (12%). Typical losses from unplanned layouts are 10-20% of total rack locations and 20% or more of power density capability.

Hot-aisle/cold-aisle layout allows a power density increase of up to 100% or more versus random or same-direction layouts, and a poor layout can cut permissible rack power by over 50% with certain cooling architectures. The step-by-step planning sequence covers constraints, layout axis selection, row-end clearances, density zoning and raised-floor index points, and closes with common errors observed in existing facilities.

Key points

1. Rack-location estimate: room area / 28 sq ft (2.6 m2) per rack.
2. Four pitches: A 14 ft (4 ft cold/3 ft hot), B 16 ft (6/3), C 16 ft (4/5), D 18 ft (6/5).
3. Pitch B gives 50% more raised-floor cooling capacity in the cold aisle; C and D suit racks with rear cooling accessories.
4. Hard-floor pitch can be compressed if aisles stay at least 3 ft (hot) and 4 ft (cold); 50 in racks give a 15 ft 4 in minimum.
5. 40-rack example: a column in an aisle drops it to 29 (over 25% loss); rotating the axis 90 degrees keeps 35.
6. Hot/cold aisle layout allows 100% or more density increase versus random layouts; a poor layout can cut permissible rack power by over 50%.
7. Row ends need at least 2 tiles to plain walls (3 preferred in large rooms); rows over 10 may need breaks; avoid rows of 1-3 racks.
8. Unplanned layouts typically lose 10-20% of rack locations and 20% or more of density capability; a misplaced partition lost 10 of 80 racks.

Using it in design

• Run the layout engine on a 600 mm / 2 ft grid with row-pair pitch presets A-D (14/16/16/18 ft), auto-selected from raised-floor, rear-door accessory, containment and density inputs.
• Rule checks: minimum cold aisle 4 ft, hot aisle 3 ft, row-end clearance at least 2 tiles; flag rows of 1-3 racks, rows over 10 racks without a break, columns inside aisles, rows facing hot-to-cold, perpendicular rows and odd numbers of rows.
• Run both layout axes automatically and report rack count per axis.
• Require surveyed column dimensions and a raised-floor index point tied to the row layout; use racks = area / 2.6 m2 as a quick estimate before detailed layout.

Who should read it

Designers laying out data halls and operations engineers investigating capacity lost in an existing facility.

Related standards

• ASHRAE TC9.9 Thermal Guidelines
• ANSI/TIA-942

Publication details

Authors

Neil Rasmussen; Wendy Torell

Publisher

Schneider Electric

Year

2015

Document number

WP 144

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