Precision Air Conditioning Systems for Computer rooms and Communications
The equipment used and housed in the computer rooms are called critical loads, which should not interrupt their operation in any way, a situation of this type can cause considerable economic losses, prestige and even human lives. Inadequate air conditioning system design is the second factor responsible for disruption in computer room operation after the electrical factor.
Nowadays computer and communication processes have taken on great relevance, because most private companies, government, schools, hospitals, banks, base their operations through these processes.
Eng. Dante Reynoso Franco
The equipment used and housed in the computer rooms are called critical loads, which should not interrupt their operation in any way, a situation of this type can cause considerable economic losses, prestige and even human lives. Inadequate air conditioning system design is the second factor responsible for disruption in computer room operation after the electrical factor. Hence the importance of analyzing the best environmental conditioning alternative for this.
It is essential to design the computer or communications room, in such a way that it allows to have a high level of quality and reliability in the basic concepts for its construction:
1. Architectural
2. Electric
3. Communication and Monitoring
4. Security
5. Air conditioning
Criteria for selecting the precision air conditioning system
We start from the idea that the room is an enclosed area in which large electronic equipment that generates high amounts of sensitive heat are housed, and therefore it is necessary to remove that heat generated in the most efficient way. This phenomenon shows the first thermodynamic law that tells us that "energy is not created nor destroyed, it is only transformed" (see figure 1).
Figure 1. In these places a large amount of sensitive heat accumulates that must be extracted in the most efficient way.
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Selection of the air conditioning system
Initially, the thermal calculation is carried out to determine the capacity of the air equipment to be installed, considering redundancy to increase reliability and availability (5 9 ́s) 99.999.
There are entities such as the Uptime Institute that makes recommendations for redundancy in categories from TIER 1 with N redundancy, to TIER 4 with a minimum redundancy N + 1. The level of redundancy depends on how critical the operation and continuity of the room is.
Subsequently, once the capacity and level of redundancy we require is determined, the cooling system is selected.
There are the following basic cooling systems in precision air conditioning equipment:
• DX direct expansion systems: Air, water and glycol cooled.
• Systems cooled by ice water.
• Mixed systems, evaporator with direct expansion coil and ice water coil.
The selection will depend on the distances between indoor and outdoor unit, if we have a distance less than 30 meters between units it is recommended to use direct expansion systems cooled by air.
In case the distance is greater than 30 meters, it is suggested to use direct expansion systems cooled by water or glycol (preferably it is recommended to use glycol, which is an antifreeze, when we have outside temperatures below 0 ° C to prevent damage to pipes).
The ice water system is used when it is determined to operate a central ice water generating system (see Figure 2).
Figure 2. Precision evaporator and condenser
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Air Distribution
If the room is projected to distribute the air through a false floor, it is advisable to consider a height of 60 to 70 centimeters to have a better distribution of it (see figure 3). But if the room does not have a false floor, there is also another alternative (see figure 4).
Figure 3. Air distribution without false floor Figure 4. Air distribution through false floor
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To be within the global ecology campaign, through energy saving and green computer rooms, it is necessary and, generally used, to use ecological refrigerants that do not damage the ozone layer such as R-407C and R-410A, as well as to use high-efficiency engines, compressors and turbines.
High Thermal Load Density
Technological advances, proposals and innovations have led to the design of servers with greater capacity and smaller size, which has caused that in fewer areas, there is a greater amount of equipment, thus generating a high heat density that can cause some conflicts (see figure 5).
Figure 5. Computer room then and now
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To counteract this problem of high density, different manufacturers of precision air conditioning have designed solutions, such as placing equipment next to the server cabinets, placing cooling equipment on top of the cabinets as a complement to the cooling equipment through the placement of false floor and other elements that may be compatible with the design.
However, there is a very efficient alternative, which is to use as support to the air distribution system to the false floor, cabinets designed for high density with chimney to the ceiling and redundant air extractors with automatic operation in case of malfunction or failure of one of them.
Finally, it is advisable to hire a Commissioning service, which is a process to ensure that the systems used for the infrastructure of the room, are designed, installed, and functionally tested, with a maintenance and operation program according to the original design.
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