Two machines, one job
CRAC (Computer Room Air Conditioner): each unit has its own refrigeration (direct-expansion compressor). Simple and independent, suited to small rooms and edge sites — every unit is its own cooling station. CRAH (Computer Room Air Handler): no compressor; uses chilled water from a central plant. More efficient at scale, so large facilities standardize on CRAH plus chillers.
A failing CRAC is a countdown timer
Machine rooms are designed N+1 — one unit of redundant cooling — which means a silent CRAC failure breaks nothing immediately; it just consumes your margin. Key advantages: real-time supply/return temperature and humidity; compressor and blower health tracked; N+1 margin visible, not assumed; cooling failures mapped to the racks at risk.
FAQ
CRAC stands for Computer Room Air Conditioner. CRAC vs CRAH: a CRAC has its own refrigeration compressor (direct expansion); a CRAH does not. How many CRACs a data center needs: enough to carry the full heat load with at least one redundant unit (N+1). What to monitor on a CRAC: supply/return temperature, humidity, compressor and blower health, and filter status.