Most small data centers start with direct-expansion (DX) precision air conditioners — each unit carries its own compressor, which makes them simple to install and easy to specify one room at a time. But as facilities add halls, floors, or heat-intensive zones, that simplicity quietly turns into a liability, and chilled-water cooling starts to win on numbers rather than preference.
The first constraint is distance. DX systems move refrigerant, and the pipe run between the indoor unit and its outdoor condenser is physically limited — the further heat must travel, the more efficiency and reliability suffer. Chilled water solves this by moving heat in water instead, which is why it becomes the standard choice in multi-hall facilities, campus projects, and anywhere the heat source sits far from where it can be rejected.
The second is maintenance and redundancy. In a chilled-water design the compressors sit in one central plant outside the white space; the units inside the room are air handlers with water coils and no compressor at all. That means routine compressor service happens away from critical IT loads, and adding a third chiller is often simpler than adding a third DX condenser row. Central sourcing also makes free cooling cheaper to adopt: economizer capacity is added once at the plant, not once per indoor unit.
The trade-off is real and should be stated plainly. Chilled water requires a water loop, pumps, water treatment, and freeze protection in cold climates — more design work and higher upfront investment. The question is therefore not which technology is more advanced, but where the project sits on load size, expansion plan, climate, and local maintenance capability. Most operators who regret the decision regret making it late, not making it at all.
HAILOS, a China-based precision cooling manufacturer, provides air-cooled chillers from 28 to 158 kW alongside chilled-water precision air conditioning units from 20 to 202 kW, with free-cooling options, custom voltage, CE certification, and low-ambient operation down to −35°C. Contact: info@hailos-hvac.com | WhatsApp +86 130 1227 2328
