What Is a CRAC Unit? Data Centre Cooling Explained (Australia)
What Is a CRAC Unit? A Plain-English Guide for Australian Data Centres and Server Rooms
Quick answer
A CRAC unit (Computer Room Air Conditioner) is a precision cooling system designed to maintain stable temperature, humidity, and airflow in environments full of heat-generating IT equipment. They are most commonly used in data centres, server rooms, network closets, and edge computing cabinets. Unlike a standard split-system air conditioner, a CRAC unit is engineered for 24/7 operation, tighter tolerances, and the unique heat loads produced by servers, switches, and storage arrays.
If you have ever walked into a server room and noticed the dry, cool, faintly humming air, that is a CRAC unit doing its job.
CRAC unit meaning: what does CRAC stand for?
CRAC stands for Computer Room Air Conditioner. The name dates back to the early days of mainframe computing, when entire rooms were filled with heat-generating hardware that needed dedicated cooling. The acronym has stuck, even though modern CRAC units bear little resemblance to those early systems.
You will often see CRAC units mentioned alongside two related terms:
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CRAH (Computer Room Air Handler), which uses chilled water instead of refrigerant
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In-row cooling and rear-door heat exchangers, newer cooling formats placed close to the servers themselves
For most Australian server rooms under a few hundred kilowatts, a traditional CRAC unit is still the workhorse. You can see the full range of precision cooling systems we supply on our CRAC collection page.
How does a CRAC unit work?
A CRAC unit uses a direct expansion (DX) refrigeration cycle, the same fundamental principle as a household air conditioner, but built to a far higher specification.
Here is the cycle in plain English:
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Warm air is drawn in from the server room, typically from the hot aisle or the room return.
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Air passes over a cooling coil filled with refrigerant. Heat is absorbed into the refrigerant.
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The refrigerant is compressed in a compressor, which raises its temperature further.
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Heat is rejected outside the building via a condenser, using ambient air, water, or a glycol mix.
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Cool, dehumidified air is delivered back into the room, usually under a raised floor or directly into the cold aisle.
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Humidity and filtration are managed continuously to keep conditions inside ASHRAE-recommended ranges.
The whole loop runs continuously, 24 hours a day, 365 days a year.
What makes a CRAC unit different from a normal air conditioner?
This is one of the most common questions we get from Australian businesses standing up their first server room. The differences are significant:
The takeaway: a CRAC unit is a purpose-built piece of critical infrastructure. Trying to cool a serious server room with comfort air conditioning is a common, and expensive, mistake.
Where are CRAC units used in Australia?
CRAC units are deployed wherever sensitive electronics generate concentrated heat loads. In our experience supporting clients across Brisbane, Sydney, Melbourne, and regional Australia, the most common applications are:
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Enterprise and colocation data centres
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On-premise server rooms for mid-sized businesses
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Telecommunications and network exchange sites
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Hospitals, pathology labs, and medical imaging suites
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Financial services and trading rooms
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Industrial control rooms and SCADA environments
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Broadcast and post-production facilities
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Defence, government, and research computing
If your site has racks of equipment running continuously, a properly sized CRAC unit will pay for itself in avoided downtime and extended hardware life. Learn more about our CRAC installation and commissioning service.
Key components of a CRAC unit
Understanding the main components helps when you are comparing quotes or planning maintenance:
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Compressor, the heart of the refrigeration cycle. Modern CRAC units often use scroll or digital scroll compressors for efficiency.
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Evaporator coil, where heat is absorbed from the room air.
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Condenser, which rejects heat outside the building, either air-cooled or water-cooled.
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EC fans, high-efficiency electronically commutated fans that vary speed based on load.
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Humidifier and reheat element, which keep humidity within the target band (typically 40 to 60% RH).
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Filters, which capture dust before it reaches sensitive electronics.
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Controls and sensors, including temperature, humidity, airflow, and pressure sensors feeding a central controller.
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Building management interface, usually Modbus, BACnet, or SNMP for remote monitoring.
A well-specified CRAC unit is not just a cooler. It is a sensor-rich, networked piece of infrastructure.
Common CRAC unit brands supplied in Australia
Indigi Power & Cooling supplies and services CRAC units from the leading global manufacturers, with full local support across Australia. The brands we work with most often include:
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Stulz, with German engineering, widely deployed in Australian data centres.
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Vertiv (formerly Liebert), one of the most recognised names in precision cooling worldwide.
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Schneider Electric (APC), popular for InRow and modular cooling.
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Airedale, Mitsubishi Heavy, and others, for specialised applications.
The right brand depends on your heat load, footprint, redundancy strategy, and budget. We also supply DX CRAC servicing across Brisbane, Sydney and Melbourne for these brands and more.
CRAC unit sizing: how do you know what you need?
Sizing a CRAC unit correctly is critical. Undersize it and you will have hot spots and thermal alarms. Oversize it and you will waste capital and run inefficiently.
A proper sizing exercise considers:
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IT load (kW), the actual power draw of the equipment, not nameplate ratings.
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Future growth, typically 20 to 30% headroom for the next 3 to 5 years.
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Room geometry, including ceiling height, raised floor, and hot/cold aisle layout.
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External envelope load, including heat gain through walls, roof, and any glazing.
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Redundancy strategy, N, N+1, or 2N depending on criticality.
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Australian climate factors, such as Brisbane summers, regional dust, and coastal salt exposure.
Our team carries out site assessments across Australia and produces a sized, branded proposal with model recommendations and indicative pricing.
Frequently asked questions
Is a CRAC unit the same as a server room air conditioner?
In everyday conversation, yes. Technically, "server room air conditioner" is a generic term, while "CRAC unit" specifically refers to a precision DX cooling system designed for IT environments.
How long does a CRAC unit last?
With proper servicing, a quality CRAC unit will run reliably for 15 to 20 years. Compressors and fans may need replacement during that life, but the chassis and core systems are built for longevity.
Can I run a small server room without a CRAC unit?
For very small loads (under 3 to 5 kW) you may get away with high-spec comfort cooling, ideally with redundancy. Above that, a purpose-built CRAC unit is the right call.
What's the difference between CRAC and CRAH?
A CRAC unit uses refrigerant in its cooling coil. A CRAH unit uses chilled water supplied by a central chiller plant. CRAH is more common in larger data centres, while CRAC is more common in standalone server rooms.
For more questions, see our UPS, battery and CRAC FAQ page.
Need help with CRAC units in Australia?
Whether you are standing up a new server room, replacing an end-of-life unit, or trying to fix a noisy thermal alarm, our team supplies, installs, and services precision cooling across Australia.
Contact our team for a site assessment, or browse our full CRAC unit range and we will come back with sized options and indicative pricing.
