Definition
CRAC (Computer Room Air Conditioner) is a dedicated cooling unit designed to remove heat from data center and server room environments while maintaining controlled temperature, humidity, and airflow conditions.
A CRAC typically uses a refrigeration-based cooling cycle, often incorporating a compressor and refrigerant circuit, to cool the air serving IT equipment. CRAC units are commonly used in enterprise data centers, server rooms, and facilities with distributed or self-contained cooling systems.
How CRAC Works
A typical CRAC cooling process includes:
- Warm air is drawn from the data center space into the CRAC unit.
- Heat is removed through a refrigeration cycle and cooling coil.
- The unit conditions the air by controlling temperature and, where required, humidity.
- Cooled air is returned to the IT environment.
CRAC units can be deployed with raised-floor systems, hot-aisle/cold-aisle configurations, and other airflow management strategies.
CRAC vs. CRAH
The primary difference between CRAC and CRAH is the source and method of cooling.
| Feature | CRAC | CRAH |
|---|---|---|
| Full Name | Computer Room Air Conditioner | Computer Room Air Handler |
| Primary Cooling Method | Refrigeration / DX cooling | Chilled water |
| Compressor | Typically included | Typically located in the external cooling plant |
| Cooling Source | Refrigerant-based cooling circuit | Central chilled water system |
| Typical Architecture | Self-contained or distributed cooling | Centralized chilled-water cooling |
| Common Application | Enterprise and smaller data center environments | Larger data centers and centralized cooling systems |
In a typical CRAC architecture, the refrigeration equipment is integrated into or directly associated with the computer room cooling unit. In a CRAH architecture, the cooling coil receives chilled water from a separate chiller plant.
CRAC in Modern Data Centers
CRAC remains an important technology for air-cooled data centers, particularly where independent or distributed cooling units are preferred.
However, increasing rack power density and AI workloads are changing data center thermal architectures. High-density environments may supplement conventional CRAC-based air cooling with technologies such as direct-to-chip liquid cooling, rear door heat exchangers (RDHx), or other hybrid cooling approaches.
In liquid-cooled data centers, CRAC units can also continue to provide room-level cooling for residual heat and IT components that are not directly cooled by liquid.
Related Terms
- CRAH (Computer Room Air Handler)
- Precision Cooling
- Air Cooling
- Chilled Water System
- Data Center Cooling
- Thermal Management
- Liquid Cooling
- Direct-to-Chip Cooling
- Rear Door Heat Exchanger (RDHx)
- High-Density Computing
- AI Data Center
Related ATTOM Solutions
ATTOM provides data center cooling solutions covering precision air cooling and high-density liquid cooling architectures for modern data center environments.
Explore ATTOM’s Precision Cooling and Liquid Cooling solutions for applications ranging from conventional enterprise infrastructure to high-density AI computing.
