Skip to main content
Back to Glossary
Cooling

Computer Room Air Handler

CRAH

Fan-coil unit that uses chilled water from a central plant to cool data hall air. More efficient than CRAC at scale.

Full Definition

A Computer Room Air Handler (CRAH) transfers heat from data hall air to chilled water supplied by a central chiller plant. Because compressor work is centralised and chiller efficiency improves at scale, CRAH-based systems typically achieve better PUE than distributed CRAC units in large facilities. CRAHs are controlled by varying fan speed and chilled water flow. In liquid-cooled facilities they handle residual non-captured heat; in air-cooled facilities they handle all heat rejection.

Also Known As

computer room air handler

Source Reference

ASHRAE TC9.9 — Data Centre Thermal Guidelines

Related Terms