Fieldbus helps to keep fire exits clear

A fieldbus-based system running on fireproof cables is providing intelligent smoke control at a London shopping centre to provide safe escape routes in the event of a fire

A fieldbus system has been installed by Keltron Controls of High Wycombe at Whiteley's Shopping Centre in London's Bayswater during a recent upgrade to the fire and safety system. It controls over 100 field devices. The heart of the system is Keltron's KCL S90C addressable control system, which is based on an industrial programmable controller, a FX0N from Mitsubishi Electric.

Smoke-free escape routes provide the safe evacuation for most large public buildings, and are ensured by adjusting motor-driven dampers to remove smoke or add 'make up air'. Each building is divided up into a number of pre-determined fire zones - eleven at Whitley - and a smoke-handling strategy is developed for every possible combination of zones being stricken with fire. These strategies are all loaded into the programmable controller's memory, with the one being selected dependent on which fire alarms, smoke, heat, and presence sensors are activated.

The KCL S90C runs independently from the main Building Management System (BMS), which is incompatible with fireproof cabling. It uses two-wire bi-directional pulse position modulated signalling to constantly monitor and address the critically important field devices, which include fans, dampers, sensors, emergency signage, recorded voice messages and tannoy facilities, door, window and fire escape actuators, a control panel and information displays for updating fire-fighters and facilities managers.

There are many advantages to using a fieldbus-based system in environment control; a critical one for the Whiteley upgrade being the low wiring requirement compared to conventional systems, which is particularly significant considering the distances involved and the number of field devices. This also makes it particularly appropriate for retrofit work, such as at Whiteley, as there is less need to make good surfaces in public areas so avoiding interruptions to business.

Whiteley's was originally an old fashioned department store, but changing attitudes to retail shopping led to the conversion of the Grade II listed building to a state of the art shopping centre with 77 independent shops, 10 restaurants, multiplex cinema, health club and rooftop parking in 1989. Strides made in digital control and environmental conditioning since then have been massive and the new smoke control system was installed as part of the centre's strategy to remain at the cutting edge of customer comfort in a highly competitive sector.

Keltron Controls

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Mitsubishi Electric

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