DCN August 2017 - Page 23

Cooling A number of challenges complicate the task of operating an efficient cooling infrastructure. Cooling system capacity is nearly always oversized owing to availability requirements, a fact made worse because data centres often operate at less than 50 per cent load. Furthermore, the amount of equipment in a data centre, and its layout, changes, forcing changes to the cooling operation as a consequence. Cooling systems are typically assembled using equipment from different vendors, with consequent challenges of compatibility and co- ordination between them. The bigger picture An effective control system should enable management to consider the overall effect of adjustments to one part of the cooling infrastructure on the installation as a whole. That in turn means that manual adjustments made to individual elements should be superseded by automatic controls as far as possible. An effective control system should shift between different operation modes like mechanical, partial economiser and full economiser mode automatically, based on outdoor air temperatures and IT load to optimise energy savings. It should also co-ordinate the operations of indoor cooling devices to prevent demand fighting between the CRAHs. IT space humidity should be centrally controlled by maintaining dew point temperatures at the IT intakes, which is more cost effective than maintaining relative humidity at the return of the cooling units. Levels of control Device level control involves the control of individual units such as chillers. Such controls are ‘An effective control system should shift between different operation modes to optimise energy savings.’ usually built into the equipment by vendors themselves. Device level controls typically do not cater for communication with other devices; rather their purpose is to ensure predictability of operation and reliability of the devices. They also act as the foundation for higher level control plans. Device level controls require less experience of data centre operators who typically adjust set points to the prevailing environmental requirements. They entail no extra capital cost because they are built into the equipment by its vendors. Nevertheless, they can achieve significant energy savings through the use of fans, compressors and pumps which can be adjusted according to IT load. Device level control on its own should typically only be used for a small UH]ۛHۙB[[] ܈^[\H]Z\Y ܛ\][۝ H^][\ Y\H[ܙ[][ۂو]\[[]وH[YH\Bو]XK[HԐR\X[BHH[YH[\X\B[܈[۝YHH[YB۝[ܚ]K\[YH\][ۂو[X[Y[[\Z]™ܙX]\[ܙ[][ۈ]Y[Y\[[]ˈ][B\X[\HYX]H[H\BوZ[\HوH[H[]X]\BY[[[][H[[[H[H[X]]Y]]X]X[H[\]Z\Y BXZ[[Z]][ۈوܛ\][۝\]][ۛH۝[Z[\]X\[\X[HۛBHH[YH[܋\[K[][۝ H^][\ [ܙ[]\H\][ۂوY\[[X\[\][H]H[K܈^[\BH[\[HԐR \[H][۝[[[ܙ[]HB\][ۈ]Y[XYY[\]ܜ[H[܈Z\[\Z[[Z\H[\H\K[Y]و\][\H]][] ^KH[Y]\\[H\X[H[ZHBوH[[ZXZ[[Z\H[[[\Hۜ[\[ۋU[[[ݙH]Y[Y\[[\و\][ۈ]][X[[\[[ۋYZ[Y H[Z]][ۈ\]X۝\[\\X[Bܚ\]\]Z\Y[BH[YH[܈[܈H[ܙB\X۝\[H܈H\B]H[K]\X\\H˜ۜY\HY\][و۝\[NX[]H][۝ HY\][X[]H][۝[Yܘ]\˜[[[ۜوHZ[[[B[[ۈ]ܚ]X[Y\™]\][[HZ[[BX][[[][ۋZ\ۙ][ۙ\˜[Y[\[\HX\]K[Y\[H\[\K\X[ۂ\[\ˈ]ݚY\H[\Z[]HX\H[\YܙB[X\H[[ܙ[]Y[YXY[[]YH[[˜[وH]H[x&\\][ۜ˂H[Y]وX[]H][۝ݙ\H\][\B]][[ۚ]܈H]\˜[\ܛX[Hو\[[\[\HB][]HۛX[ۈYۈHU\\ˈ][[[\HB\[[Y\[[\ۛXY]\Hو[\X\H\ۙ[˜[[][X]HYX][B]]H[H\]ܜˈ][[\H[ܛX][ۈ]\[\X\HX[Y[Y[\[\[[[XZ][]\[[\H[ܛX][ۈ]Y[[XX[\[ۚ]ܚ[\[\ TTB[]H[H[\X\BX[Y[Y[ SJH\[\˂܈\\]H[\X[]B][۝\Y\XH\HYX[›و[\[YXY[\][ۋYX[\ۜ[\[ۈ[XX[[XZ[Z[[Hœ\\YHYX][\][˂]Y\ M