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Precision Air Conditioning (PAC)

The precision air conditioners , also known as a CCU (close control units) or CRAC (computer room air conditioner) are refrigerating equipment specifically designed to provide precise control of temperature and humidity in all applications in which is required a very high degree of precision.

The role of the precision air conditioners is cooling and dehumidification. Control is performed by heating and humidification, and it is desired that the refrigerator is in continuous operation at a stable and constant speed. Stops defrosting etc., care must be taken to supress changes due to surrounding environment.

Modern IT, Telecommunication & laboratory equipment generates a large amount of heat and the problem increases with higher density IT kit (e.g. Blade Servers). It is, therefore, essential to use the correct type of cooling and to understand the air flow requirements within the room. Failure to achieve this can have disastrous results with 'deadly' hot-spots happening just where you don't need them - around your key mission critical servers.

Electronic and information processing equipment require rigid environmental conditions for reliable operation with precised control of temperature & humidity. Computer Room precision air conditioning systems are specifically designed for the concentrated vertical heat loads of today's Data Centers.

Computer Room air conditioners are commonly known as Precision Air Conditioners or Close Control Unit (CCU) or Computer Room Air Conditioner (CRAC). Close Control Unit (CCU) provides efficient heat removal, excellent humidity control, greater airflow, better air filtration, greater flexibility and expandability, and numerous alarm and redundancy options. It is available in up flow or down flow type based on air throw. Based on coolant & position of coil it is broadly classified into Chilled water (CW) type and Direct Expansion (DX) type.

Key Benefits of CCU or CRAC over Conventional air Conditioner:


  • Precise control of Humidity & temperature along with cleanness : Electronic & Information processing equipments require a system that provides precise humidity control to meet equipment specifications and air filtration designed to keep airborne particles from causing problems with critical equipment. PAC precisely controls humidity and Temperature with filtration.

  • Reliable operation for 365 days a year : Most of critical application requires 24x7 availability of cooling environment with precise control of temperature and humidity. PAC is designed for 24 x 7 applications.

  • Cooling of Critical Spaces : Energy efficiency is no longer just an option for users of air conditioning. There are down flow systems for raised floor facilities and up flow units where the floors are not raised. Supplemental systems can be used where equipment is tightly packed in racks. Compact models are ideal for small or remote facilities.

  • Energy Saving : PAC systems offer a choice of compressor types, microprocessor controls and other optional features designed to reduce power consumption and maximize energy savings which help in fast return of investment.


Some of the common names uses for close control units are server room air conditioner, server room ac, server room cooling system, server room air conditioning, datacenter cooling calculator, server room cooling calculator, close control air conditioning, precision air conditioning unit.