Air cooling runs out of room somewhere in the tens of kilowatts per rack. Past that point the facility has to bring liquid to the rack, and the colocation contract has to say who provides what.
The three approaches
| Method | What the facility provides | What you provide | What goes in the contract |
|---|---|---|---|
| Rear-door heat exchanger | Chilled water to a door coil on the rack | Standard servers, no changes | Water loop to the rack, leak detection, door spec |
| Direct-to-chip liquid | Coolant distribution units feeding cold plates on the CPUs and GPUs | Liquid-ready servers and manifolds | Who owns the CDU, coolant quality, temperatures, maintenance windows |
| Immersion | Servers submerged in dielectric fluid in tanks | Immersion-rated servers, tank vendor | Floor loading, fluid handling, warranty terms, remote hands training |
How it changes the deal
Liquid cooling adds a line of shared equipment between your servers and the building. Ask who owns and maintains the coolant distribution units, what supply temperature the facility commits to, how a leak is detected and handled, and what remote hands are trained to do. Then price it: some facilities charge for the cooling capacity as a separate line, others fold it into the power rate.
Density and delivery
Liquid-ready space is the scarcest kind of colocation. Ask each bidder for the date the cooling is live in your rows, not just the date the space is available. The AI and GPU page has the density math from the server up.
Questions to ask every bidder
- Which cooling methods are live today, and in which halls
- The kW per rack committed with that method
- Supply and return temperatures, and the facility's response if they drift
- Who supplies, owns and services the CDUs and manifolds
- Leak detection, isolation and the SLA that covers it
Questions
When the rack's heat exceeds what the facility can remove with air in that hall. Ask each facility for its air-cooled limit per rack; above it, you're choosing between rear-door heat exchangers, direct-to-chip liquid or immersion.
The cooling equipment and its maintenance are new lines, but higher density per rack can reduce space cost. Compare the full 36-month cost with every line counted.