Jun 17th, 2008 by Floriano Monteduro
One of the problems commonly faced during the design of a datacenter is the proper choice of the cabinet and before stepping into any decision it is necessary to consider all the different physical and environmental conditions that the new generation of active equipment requires. Space optimization due to high costs of the infrastructure requires more concentration in the same cabinet therefore it is necessary to select cabinets with a minimum load bearing of 750 kls. Keeping unaltered the functionality of the cabinet itself: copper and fiber optics cable management, ant topple devices to prevent dangerous movement during maintenance operations. All the mobile components of the cabinets must be interconnected with the cabinet frame and this one put suitably to ground. This operation which is too often not properly carried out avoids electrostatic discharges when the percentage of relevant humidity falls between 45% and 50%. Today all server manufacturers recommend the maximum airflow to reach the electronics inside the cabinet.High rate perforated doors with a minimum empty surface of 80% installed on the front side of the rack fully comply with this recommendation and give the considerable advantage to check all the equipment “at a glance”. The same criteria is to be adopted on the rear part of the cabinet keeping carefully power and network cables out of the hot airflow and suitably cabled into proper management trays. It is clear how the new parameters change the previous layout based on the “chimney” effect using front glass and rear blank doors.The chimney effect shows us all the limits of this application even if still used in small installations: the performances of the cold airflow coming from raised floor directly inside the cabinet it is easily compromised by heavy equipment that for obvious reasons is positioned at low level in the rack.Besides the reduced space between the door and the front side of the servers is not enough to guarantee the necessary airflow. Closing spaces on the 19” can furthermore prevent hot air coming from servers to go back on the front part of the cabinet causing “short circuits”.
Tags: , 19", air flow, cabinet, frame, perforated doors, rack
Posted in Air Conditioning, Generic
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A greater consideration often overlooked is the layout of the cabinets (including the hot/cod aisle configuration) in relation to the positioning of the CCU’s/CRAC’s. Often I have seen a cold aisle located in the centre of the return path of the CCU/CRAC - a few feet left or right would optimise the cooling and improve efficiencies. The same can be said for the vented tiles which are then deployed in the cold aisle in close proximity to the CCU/CRAC causing further short-circuits resulting in the unit working less efficiently based on the percieved return air temperature.