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The alarm sequence for total flood extinguishing systems is governed by European and international standards. Here FSE reviews and installation where programmable sounders were interfaced with the extinguishing panel to provide a clear and manageable solution.
The alarm sequence required for gaseous, total-flooding fire extinguishing systems is prescribed in British, European and International standards. The sequence typically has four stages: the first indicates that a single detector has operated, and that action is required; the second stage indicates that two or more detectors have operated and is known as ‘coincidence’ alarm, confirming the fire and that the extinguishing system discharge is imminent (normally comprising a pulsing tone. A third stage, with a different frequency of pulse, is effected when someone has operated a hold button to delay the gas discharge – hold buttons being necessary if the system is to be left in the ‘automatic’ mode while the protected area is occupied. The fourth stage, with a constant tone, confirms that the gas has been discharged.
At each of these four stages there is a distinctive audible alert signal and the first stage is also normally accompanied by a flashing beacon, which continues to strobe through the other stages. Unfortunately, however, those who are less familiar with these alarms may not immediately be aware of the meaning of each stage.
In order to provide such a complex sequence of alarms it has, in the past, been necessary to use multiple devices – bells, beacons and composite electronic sounders. Mounting several devices on a wall is unlikely to add to the aesthetic appeal of the room in which they are fitted, and can also add significantly to the cost of installation.
Vehicle auction company British Car Auctions had a gaseous fire extinguishing alarm system to protect their IT centre, which followed these four stages. But their IT operations manager was not overly satisfied with the clarity that this complex alarm, sounder and beacon arrangement offered.
New system
With these considerations in mind, Siemens Building Technologies partnered with sounder experts Klaxon. The company had a programmable annunciator which, from a single unit, could produce all of the tones and visual signals prescribed for use with gaseous total flooding fire protection systems, plus more. Even better, the units could also produce voice messages that would remove any ambiguity about the stage of alarm, as well as providing clear instructions on the appropriate action. However this arrangement would have to interface to an EN 12094 compliant extinguishing control panel without generating conflicting messages.
Siemens worked with Klaxon to interface these annunciators with its XC10 extinguishing control panel – and with others panels complying with EN 12094 – to optimise configuration and field application. The result of this process was installed at British Car Auctions’ headquarters. There, a Nexus annunciator operated directly from the extinguishing control system was installed. This provides the requisite combination of tones and visual alerts prescribed in the standards, with enhanced beacon functionality, while the tones are supplemented by voice messages. The second stage message, for example, says: “… the CDT nitrogen release is imminent. Please evacuate the area!” and the beacon gives a double-flash at regular intervals, in place of the single flash associated with first stage.
The new set-up at British Car Auctions is used as part of the Siemens Sinorix CDT nitrogen extinguishing system to protect the company’s IT installation. To complement the Nexus voice annunciator on the Sinorix extinguishing system, a compact single message Sonos annunciator, which also has an integral LED beacon, was installed outside the protected area. Triggered by a high sensitivity smoke detector which is separate from the extinguishing system and after producing the required tone, this unit generates the alarm message: “Attention, attention. The aspirating smoke detection system has operated – action required!” to draw the attention of staff to the potential problem at its incipient stage, so they can attempt to contain it and thereby prevent it from escalating to the point where the extinguishing agent is released.
Beyond reasonable doubt
The other messages are equally clear and straightforward, leaving no doubt over exactly what is happening, and what actions are appropriate. The new annunciators were easy to install and, because only a single unit is needed rather than multiple sounders plus a beacon, the time required for installation and wiring was reduced. This means that, although the annunciators are more expensive than traditional types, the overall cost of using them is almost the same in small installations and appreciable savings are possible on larger ones. Also, the use of a single unit, rather than several, means that the aesthetics of the installation are greatly improved.
The interfacing units have now been designed to cover all gaseous agents addressed by BS ISO 14520. A variant is also available for carbon dioxide systems addressed by BS 5306 Part 4.
“We were very pleased with the speed with which Klaxon were able to develop this product for us and have completed the installation at British Car Auctions’ headquarters,” commented Chris Downing of Siemens Building Technologies. “We also appreciate that there are a number of applications that could use this product, so we have encouraged Klaxon to develop this technology for the benefit of the whole fire protection industry, not just for Siemens, perhaps to become a future industry standard.