Data centre operators face increasing thermal loads from high-density computing environments, especially with the rise of AI workloads and edge computing. While Computer Room Air Handlers (CRAH) have formed the foundation of traditional air-based cooling systems, many operators are now investigating or switching to liquid cooling systems to fulfil performance and efficiency requirements. However, this transition necessitates meticulous planning, infrastructure modification, and a thorough understanding of compatibility, dangers, and long-term benefits.
Limitations of CRAH in High-Density Environments
CRAH units are effective for air-cooled systems and are widely used in conventional data centres to manage heat through chilled water coils and fans. However, they begin to struggle when thermal loads exceed 20–30 kW per rack. Air’s low thermal conductivity compared to liquids limits its efficiency in cooling dense workloads. CRAH systems often require increased fan speeds to compensate, which leads to higher energy consumption and operational costs. Additionally, as workloads evolve to include AI training clusters and GPU-intensive tasks, the cooling demands outpace what CRAH units can provide sustainably.
Liquid Cooling as a High-Density Alternative
Liquid cooling systems, including direct-to-chip and immersion cooling technologies, offer far greater thermal efficiency by transferring heat directly from the source using coolants with higher heat capacities than air. A liquid cooling system can manage rack densities exceeding 50 kW, with improved temperature control and reduced power consumption for cooling (lower PUE). These systems enable data centres to operate high-performance computing (HPC) loads more effectively and are aligned with sustainability goals through reduced reliance on large-scale air movement and mechanical chillers.
Infrastructure Readiness and Compatibility
Transitioning from CRAH to a liquid cooling system isn’t plug-and-play. It involves a significant overhaul of rack architecture, piping, and facility layout. Data centre operators must assess their chilled water loop, floor loading, and spatial zoning. Some operators may opt for a hybrid model initially, using CRAH units to cool legacy systems while liquid cooling supports newer deployments. Rear-door heat exchangers and direct liquid cooling modules can bridge the two systems in such scenarios. However, integration challenges include ensuring coolant containment, redundancy, and water treatment protocols to prevent corrosion or microbial growth in cooling loops.
Cost Considerations and ROI
The upfront cost of deploying a liquid cooling system is higher than maintaining CRAH units, primarily due to custom infrastructure, engineering work, and retrofitting needs. However, liquid cooling often results in lower operational expenditure over time due to reduced energy consumption and less reliance on CRAC/CRAH equipment. Additionally, by supporting higher densities in the same footprint, data centres can defer the need for physical expansion. The total cost of ownership becomes favourable when operators account for efficiency gains, lower failure rates of hardware, and compliance with ESG standards or carbon reduction mandates.
Training and Operational Shifts
Managing a liquid cooling system requires new skill sets for facility teams. Staff trained in HVAC and traditional CRAH operations may need certification or upskilling to handle the plumbing, pressure regulation, and monitoring systems associated with liquid-cooled environments. Emergency response procedures and maintenance protocols also shift, especially when dealing with dielectric fluids in immersion setups. Proper vendor partnerships, documentation, and support contracts are essential to maintain uptime and performance during and after the transition.
Conclusion
CRAH units alone may not be sufficient to handle escalating heat loads as data centres become more compute-intensive. Transitioning to a liquid cooling system is a forward-thinking option that improves efficiency and sustainability, but it necessitates careful planning and investment. A phased or hybrid plan, combined with good operational readiness, can help ease the migration while balancing performance and practicality.
Visit Canatec today to future-proof your data centre with smarter cooling.