From 15 kW to 80 kW: what changes when a hall goes AI

Most data halls in service today were designed for air-cooled racks drawing 5 to 15 kW. AI training racks routinely land between 30 and 80 kW, and the newest rack-scale GPU systems go past 100 kW. That is not a tweak to an existing design. It changes the electrical, mechanical, and structural basis of the room.

The good news is that the shell, the site, and often the utility service can stay. The work is everything inside.

Power distribution

Each rack now needs far more power, delivered through fewer and larger feeds. That means higher-capacity rack PDUs and busway, and often higher-voltage distribution closer to the rack to keep currents and cable sizes manageable. Upstream, UPS and switchgear blocks are resized around the new density, and the protection studies, including selective coordination and arc flash, have to be redone.

Cooling

Air alone runs out of headroom at these densities. Rear-door heat exchangers can bridge moderate densities. For the highest, direct-to-chip liquid cooling becomes the main path, with air handling the remainder.

Liquid brings new equipment and new disciplines into the white space: coolant distribution units, secondary fluid loops, manifolds and piping, leak detection, and water quality management. It also adds commissioning steps that many teams have not run before, such as flushing, pressure testing, and fluid sampling.

Structure

This is the part that gets missed. A fully loaded, liquid-cooled AI rack is far heavier than the racks most halls were designed around. Raised floors may need reinforcement or removal in favor of slab-on-grade. Check slab capacity and point loads, and walk the delivery path: the dock, the corridors, and any elevators the racks have to cross.

Space and layout

The same power envelope now feeds far fewer racks. Rows get shorter, containment changes, and floor space is needed for coolant distribution units and manifolds. A hall can look half empty and still be at full power.

What usually stays, and what usually goes

• Usually stays: the building shell, the site, the utility service if capacity allows, and parts of the central plant.
• Usually goes: raised-floor air distribution, the existing cooling unit layout, rack PDUs, and much of the cabling.

A retrofit checklist

1. Confirm utility and upstream capacity for the new load.
2. Redesign the electrical one-line around the new block sizes.
3. Choose the cooling topology, and the split between liquid and air.
4. Run a structural survey of the floor and the delivery path.
5. Write a liquid commissioning plan before the first pipe goes in.
6. Plan a phased cutover if any part of the hall stays live.

Treat an AI retrofit as a new build inside an existing envelope. Budgets and schedules that assume a refresh are where these projects go wrong.