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Drive Towards a Flexible Solution

Variable speed drive technology is being widely used at Canary Wharf in London's Docklands to help achieve low noise and energy-efficient air handling.

The size of a small town, Canary Wharf is a significant urban community in its own right. Developed with the help of leading architects and designers, the site is host to a daily working population of around 42,000 people.

Reflecting the effort put into the look and feel of the development, Canary Wharf Contractors Limited took equal care when it came to specifying air handling systems for commercial office premises. The requirement was for a low-noise, space-saving solution flexible enough to accommodate tenants' needs across a range of requirements and changing patterns of occupancy throughout a 24-hour period. With air handling units being sited on the actual office floor, acoustics were also a prime consideration.

Specialists in HVAC electronics Alldales Drives Systems and noise control and acoustic engineering experts IAC provided the answer, applying their joint expertise to develop a purpose-designed solution. The result was an integrated approach, based on an all-in-one compact prefabricated air handling unit incorporating Alldales' variable speed drive technology, capable of being delivered to site pre-wired and ready for installation.

A prefabricated approach offers a number of advantages, not least in building construction. Unlike the main rooftop and basement air handling and extraction systems, which have to be built on site during construction, the on-floor systems have the advantage that they can be lifted into place as a finished unit. Lightweight walls are then added allowing completion of on-floor plant rooms in as little as half a day, for a faster hand-over prior to fitting-out.

Key to the all-in-one solution, Alldales’ variable speed drives effectively provide 'plug and play' functionality in use, eliminating the need for separate motor control panels. This, together with the all-in-one nature of the air handling unit and on-floor location reduces the amount of ductwork required, simplifying the installation process. Less ducting also means reduced resistance, delivering energy savings.

Individual air handling units - there may be anywhere between two to four per floor - are linked by fibre optic cabling. Alldales' variable speed drive technology acts as lynchpin between the on-floor air circulation units and main building systems, independently gathering data and interacting with a range of Building Management Systems (BMS) to automatically adjust air flow in line requirements.

A 'zonal' approach to air control provides improved flexibility, resulting in a more comfortable environment in individual work areas. Adjustability is useful at Canary Wharf, where tenants' requirements may vary significantly between building levels. Trading floors for example with their high level of activity and computer workstations tend to generate more heat than an ordinary office environment while temperature control in central computer server rooms is critical within a tight tolerance band.

Variable speed drive technology also contributes to the whisper quiet operation of the air handling units, removing annoying' hums' and keeping operational noise down that might otherwise disrupt concentration or affect hearing, through 'soft' starting and stopping of motors and harmonics reduction.

As well as meeting the specifications laid down by Canary Wharf's contractors, the all-in-one approach scores in terms of energy efficiency over other control methods.

Typically, motors running HVAC systems operate continuously throughout the day. By regulating motor speeds to match occupancy patterns, variable speed drives can literally halve energy consumption, with an exponentially greater saving in energy in proportion to motor speed reduction to the power of three, known as the 'law of the cube'. Multiply this by all the floors in the 15 buildings at Canary Wharf and this represents a significant contribution to meeting Government targets for reduction in usage as well as delivering cost savings.

Geoffrey Crowhurst, director of IAC's Building Services Division, comments: "The reliability and superior technology offered by Alldales' compact, HVAC-specific designs offer clear advantages over traditional variable pitch impeller control methods."

The new air handling system has been universally deployed throughout the fifteen buildings at site, with the 500th unit recently installed, and further installation scheduled in buildings to be constructed in 2003.

Alldales Drive Systems' involvement with Canary Wharf continues elsewhere on site. For example, Alldales has also been commissioned to provide ongoing HVAC support for a number of buildings leased to Credit Suisse and has recently carried out a detailed consultation exercise for the company, resulting in the reduction of excessive harmonics particular to the building systems in use.

Published March 2003

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