Computer Room Air Handling Unit (CRAH) Explained: How It Works & Where to Use It
Data centers generate concentrated, continuous heat loads that standard comfort-cooling AHUs aren’t built to handle. A Computer Room Air Handling Unit (CRAH) is purpose-built for that job — tying into a central chilled water plant to deliver precise, high-density cooling to server rooms and data halls. Jaideo Automation supplies the York MC Computer Room Air Handler.
What Is a CRAH?
A CRAH is an air handling unit dedicated to cooling IT and data center white space. It draws hot air returning from server racks, passes it across a chilled water cooling coil, and supplies conditioned air back into the room — typically through a raised floor or overhead ducted path — at the tight temperature and humidity tolerances mission-critical equipment needs.
How a CRAH Works
Unlike a packaged comfort-cooling AHU, a CRAH has no integral refrigeration circuit of its own. It relies entirely on chilled water supplied by the building’s central chiller plant, using a coil, fans, and filters to move and condition air. That dependency on central chilled water is what allows CRAH units to scale efficiently across a large data hall — the compressor work happens once, centrally, at the chiller, rather than being duplicated in every unit on the floor.
CRAH vs CRAC: Key Difference
The two terms are often used loosely, but they describe different equipment:
- CRAH (Computer Room Air Handler) uses chilled water from a central chiller plant — no onboard compressor
- CRAC (Computer Room Air Conditioner) has its own integral DX refrigeration circuit and compressor, cooling independently of a central chiller
CRAH units are generally the more efficient choice at data center scale, since they share one central chiller plant instead of running many separate compressors.
Why Data Centers Use CRAH Units
- Ties into existing chilled water infrastructure instead of adding standalone refrigeration
- Compact footprint allows side-by-side installation with no gaps, maximizing usable gallery space
- Gallery-side maintenance access to fans, filters, electrical, and coil drain/vent without disrupting adjacent units
- Supports low pPUE targets with UPS and ATS redundancy options for mission-critical uptime
Applications
- Hyperscale and colocation data centers
- Enterprise server rooms and data halls
- Telecom central offices and network equipment rooms
- Any facility running a central chilled water plant that needs precision cooling for IT loads
How CRAH Fits Alongside Other Air Handling Units
A CRAH is a specialized variant of the broader AHU category, optimized for continuous, high-density IT heat loads rather than general building comfort cooling. For standard commercial and institutional applications, see our Standard Air Handling Unit guide.
Frequently Asked Questions
What does CRAH stand for?
CRAH stands for Computer Room Air Handler, a chilled-water air handling unit built to cool data center and server room IT loads.
What is the difference between a CRAH and a CRAC unit?
A CRAH uses chilled water from a central chiller plant and has no onboard compressor, while a CRAC has its own integral DX refrigeration circuit and cools independently.
Why do data centers prefer CRAH units over CRAC units?
CRAH units share one central chiller plant instead of running many separate compressors, which is generally more efficient at data center scale.