New-generation network cooling systems have halved previous cooling costs. These pages explain how these savings have been achieved.
1) Introduction || 2) Design Goals || 3) Design Performance Criteria || 4) Existing Cooling Systems|| 5) Outside UK Air Temperatures || 6) The New Cooling System || 7) Cooling System Controls || 8) People Comfort || 9) Maintenance of the New Cooling System || 10) Conclusions || 11) Acknowledgements and References || 12) Cooling System Flow Animations
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Introduction
Switching and transmission equipment dissipate heat into the immediate environment. This heat must be removed so that the space temperature stays within predetermined limits and the equipment is not damaged by the effects of excess temperature.
Until recently, space temperatures were held at a nominal 24°C, this being deemed a suitable temperature for both equipment and people. Cooling, at all but the smallest installations, was done using outside air ventilation during the cooler parts of the year and by refrigerative cooling during the warm summer days.
Several factors have now enabled the development of a new, cheaper cooling system for application to new multiple-suite switching installations. The new system has halved previous cooling costs. The factors that prompted the reassessment of cooling methods are as follows:
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A European Telecommunications Standard for room temperature and other environmental conditions has introduced ETS 300 019, published in 1992, defines the allowable room temperature and humidity range within which the equipment must work. The Standard is intended to apply to all telecommunications equipment sold within, or to, Europe. This enables a UK cooling system designer to design a cooling system which provides a Standard environment suitable for any type of equipment purchased from anywhere in the world.
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Equipment rooms are largely unattended. Fifteen years experience with digital switching and transmission systems combined with the development of remote monitoring and control has led to equipment rooms becoming unattended. The room environment no longer has to be suitable for permanent occupation and need only cater for short term visits.
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There is a long-term need to eliminate chlorine-based refrigerants in accordance with the Montreal protocol and subsequent European Directive, Chlorine-based refrigerant gasses, if released into the atmosphere, damage the ozone layer. Containment is one option, but this can be difficult to achieve in practice. Alternative refrigerants have their own problems. Elimination of all refrigerants is the preferred solution.
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BT has successfully introduced a cost-reduction culture. It is everyday business to exploit ways of reducing costs. Cooling policy and provision reflect this
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