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Inverter drive technology offers new approach to fire safety in multi-level buildings

At a time when fire safety has come into sharp focus, with the proposed implementation of the Regulatory Reform (Fire Safety) Order 2004 placing new onus on building owners and their contractors, Alldales Drive Systems has achieved a 'technical first' by developing a new fire mode for its inverter drives to secure stairwells at the exclusive residential development in London known simply as 'The Knightsbridge'.

The new mode, sanctioned by the City of Westminster, can be speedily activated in an emergency situation to operate in 'fire mode'. Normal drive programme settings in designated escape stairwells are overridden, effectively running the fans at full speed 'to destruction'. This ensures positive pressure levels are maintained throughout, preventing smoke ingress.

Offering an alternative to the installation of hard-wired starters for emergency backup, the new inverter drives can deliver cost and time savings during construction by cutting cabling and hardware requirements. Acceptance of the new design by the authorities could pave the way for more inverter drives to be incorporated in new buildings in the future for ventilation and pressure control, exploiting the precision and superior safety performance of the energy-saving technology.

Located between Hyde Park and Harrods, the high profile development at 199 Knightsbridge provides 201 apartments in total including 9 mews and 7 distinctive penthouses dubbed 'The Crown jewels' housed within a 1.7 acre site that also includes on-site swimming pool and health club facilities.

In common with all multi-storey buildings, the design of the complex includes designated 'emergency' stairwells.

Connected to the building's normal ventilation systems, these stairwells are typically fitted with fans set to maintain air circulation to a required minimum. In the event of a fire, it is vital a positive pressure is maintained within the stairwell chamber, to prevent a 'funnel' effect, whereby smoke could be drawn into and up through the stairwell rather like a chimney.

However, over-pressurisation can make it difficult to open doors onto the stairwell landings, reducing the safety escape factor greatly. The installation of a pressure sensor coupled to an inverter drive provides a self-adjusting safety mechanism, with fan speeds able to respond rapidly to compensate for the opening of doors without creating the problem of over-pressurisation. The use of inverter drives in this way replaces the need for mechanical pressure relief dampers to be installed.

Despite the superior safety advantages of inverter drives in use, widescale adoption has been restricted by the requirement hitherto by local authorities for the separate installation of hard-wired starters to bypass the inverter drive programming in the event of a fire to force fans to run at full speed.

The result of further research by Alldales to overcome these restrictions has been the addition of the new 'fire mode', which will now feature as standard in the company's inverter drives.

Released May 2005

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