What is a CRAC unit?

A CRAC unit removes heat generated by IT equipment (servers, storage, networking) and maintains tightly controlled environmental conditions required for reliable operation.

Unlike comfort air conditioning, CRAC units are engineered for:

• 24/7 continuous operation

• High sensible heat ratios

• Precise temperature and humidity control

• High airflow at low temperature differentials

How a CRAC Unit Works

A CRAC typically operates using a direct expansion (DX) refrigeration cycle:

1. Hot return air from servers enters the CRAC unit.

2. Air passes over a DX cooling coil containing refrigerant.

3. Heat is absorbed by the refrigerant and rejected outdoors via:

• An air-cooled condenser, or

• A water-cooled condenser / cooling tower

4. Conditioned cold air is supplied back to the IT space, often through a raised floor or overhead ducting.

5. Humidity is controlled via reheat and humidification systems.

Typical Applications

• Data centers

• Server rooms

• Network operation centers (NOC)

• Telecom facilities

• Control rooms

• Financial trading floors

CRAC vs. CRAH: Key Difference

Advantages of CRAC Units

• Precise environmental control

• Independent operation (no chilled water plant required)

• Fast response to load changes

• Modular and scalable deployment

• High reliability for mission-critical IT spaces

Limitations

• Higher energy consumption compared to CRAH systems

• Limited free-cooling capability unless integrated with economizers

• Less suitable for hyperscale data centers

Summary

A CRAC unit (Computer Room Air Conditioner) is a precision DX cooling system purpose-built for IT environments. It ensures stable temperature and humidity, protects sensitive electronics, and supports continuous, high-density computing operations—making it a foundational component of traditional data center cooling architectures.