CRAC vs. CRAH

I had this come up recently… what is a CRAC (pronounced ‘crack’)?  What is different from it than a CRAH (pronounced ‘craw’ or ‘cray’)?

CRAC = Computer Room Air Conditioner

A CRAC is often thought of as having an internal compressor, thus not needing the support of a centralized chilled water system.  But this also means it has to reject heat somewhere – like to a coupled rooftop drycooler.  A CRAC is also thought of as having refrigerant internal to the system, and with those extra motors and parts they need more maintenance care and have higher failure rates.

CRAH = Computer Room Air Handler

A CRAH is essentially a specialized air handling unit for computer room environments.  Most are a simple fan arrangement with an internal coil supported by a centralized chilled water system.

Clients may decide to go with one nomenclature or another, but knowing the difference can be important when working with design engineers, operations personnel and clients.

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