In Data Centres, Keeping Cool Where It Matters Most

CRAC vs CRAH Systems and What It Takes to Maintain Stable Environments

Cooling in data centres is not just about temperature control. It directly supports uptime, equipment performance, and operational continuity. As workloads increase and environments become more complex, the way cooling systems are designed and managed becomes a critical part of facility operations.

Here we explore how CRAC and CRAH systems are used in data centres, when each is applied, and what it takes on the ground to keep environments stable.

What Are CRAC and CRAH Systems in Data Centres?

Data centres rely on two primary cooling systems:

• CRAC (Computer Room Air Conditioner)
• CRAH (Computer Room Air Handler)

While both regulate temperature and airflow, they differ in how they operate and where they are most effective.

CRAC Systems are Practical for Smaller Data Centres

CRAC units use a compressor and refrigerant system, similar to standard air conditioning. They are self-contained and operate independently.

According to OCS Malaysia Data Centre SME, Mr. Dheventhiran Krisnan:

Where CRAC systems are typically used:

• Small to mid-sized data centres
• Facilities without chilled water infrastructure
• Lower-density environments (typically below 200 kW load)

Key characteristics:

• Easier installation and deployment
• Lower upfront cost
• Independent operation
• Higher maintenance frequency due to mechanical components

CRAC systems are commonly selected where flexibility and simplicity are required.

CRAH Systems are Built for High-Density Environments

CRAH systems use chilled water from a central plant to cool air through coils and fans. They are typically deployed in larger, high-demand facilities.

Mr. Dheventhiran explains:

Where CRAH systems are typically used:

• Large-scale or hyperscale data centres
• High-density environments
• Facilities with central chiller systems

Key characteristics:

• Higher energy efficiency at scale
• Strong cooling capacity
• Lower long-term operational cost
• Dependent on central chilled water systems

CRAH systems support environments where cooling demand is continuous and significantly higher.

CRAC vs CRAH: Key Differences

Beyond Equipment: What Keeps Cooling Systems Reliable

Cooling performance depends on more than system selection. It relies on how systems are managed, monitored, and maintained over time.

1. Airflow Management

Airflow is a key factor in cooling efficiency.

• Proper containment reduces hotspots
• Balanced airflow improves system performance
• Poor airflow increases energy consumption and risk

2. System Integration

Cooling systems are part of a wider infrastructure, including:

• Chiller plants
• Building Management Systems (BMS)
• Power and redundancy systems

For CRAH systems, overall performance depends heavily on the stability of the central cooling plant.

3. Maintenance Strategy

Cooling systems require structured maintenance approaches, including:

• Planned preventive maintenance (PPM)
• Condition-based monitoring
• Predictive maintenance using sensors and data

These approaches help ensure systems operate reliably across their lifecycle and reduce the likelihood of failure

4. Risk Management in Live Environments

Common risks in data centres include:

• Water leakage
• Temperature fluctuations
• Equipment strain under high loads

As Mr. Dheventhiran highlights, these are not theoretical risks but operational realities that must be actively managed.

The Role of Operations in Maintaining Stability

Cooling reliability is shaped by how consistently systems are managed on site.

Mr. Dheventhiran notes:

OCS teams support data centre environments through:

• Routine inspection and maintenance of CRAC and CRAH systems
• Airflow optimisation and containment strategies
• Real-time monitoring via CAFM, BMS, and IoT systems
• Rapid fault detection and response

This reflects a broader hard services approach where systems are managed to operate safely, efficiently, and reliably over time.

Supporting Uptime Through Structured Operations

In data centres, cooling is directly linked to uptime.

Maintaining stable environments requires:

• Preventive maintenance discipline
• Clear escalation and response protocols
• Continuous monitoring of system performance
• Skilled teams operating within defined procedures

Whether managing smaller CRAC-based facilities or large CRAH-supported environments, the objective is always to maintain conditions that allow critical infrastructure to operate without disruption.