There are principally two types of data center cooling solutions: computer room air conditioners (CRACs) and computer room air handlers (CRAHs). Which technology is the best choice for each installation depends on various factors, including climate and data center size and configuration, and that's why Trane offers catalog, semi-custom or customized cooling solutions.
Trane's CRAC units are direct expansion (DX) systems in which air used for cooling the room passes over a cooling coil filled with refrigerant. DX systems operate in a continuous closed loop using a compressor and refrigerant gas to transfer heat from the computer room’s evaporator to the outdoors through either air, water, or glycol. CRACs have a low acquisition cost; offer single- or multi-stage compressor arrangements, including tandem configurations; and they provide dehumidification, which lowers the risk of IT equipment corrosion and prevents electrostatic discharge.
On the other hand, CRAHs use chilled water in a closed or open loop system to provide cooling. The air handler collects the data center’s warm air, which then blows across a chilled water coil within the air handler. These coils contain chilled water, and the return water is pumped back to an air or water-cooled chiller. An air-cooled chiller is mounted either on the roof, on a stand, or in a mechanical yard next to the building, where it releases its heat energy in a condenser, while a water-cooled chiller is contained within the building and pumps return water to a cooling tower. CRAHs offer low PUE because they can work with air- or water-cooled chillers incorporating water side economization (“free” cooling). Multiple air handlers and chillers can connect to a single chilled water loop, making CRAHs ideal for larger installations