| Feature | CRAC | CRAH |
|---|---|---|
| Cooling method | Direct expansion (DX) refrigeration | Chilled-water coil from the closed loop |
| Compressor | Yes (onboard) | No — the chillers supply the cold |
| Heat rejection | Its own air-cooled condenser | Central air-cooled chillers, then outdoor air |
| Capacity control | Compressor staging | Chilled-water valve + fan speed + branch bypass |
| Water connection | None — never fed chilled water | Chilled-water supply and return with branch bypass |
| Best fit | Small or edge rooms with no central plant | Halls served by the central chiller plant |
| Efficiency at scale | Limited by many small compressors | High — one efficient central plant serves every branch |