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EN54 -22 

Line type heat detectors                                                                                    

DRAFT BS EN54 Fire detection and fire alarm system - Part 22:

 There have been references made to the above DRAFT standard  either by certain individuals or Corporate bodies which clearly indicate a misunderstanding of current  EN54 requirements in relation to line type heat detection systems.

 First and Foremost there currently exists NO ACTIVE STANDARD FOR ANY LINEAR TEMPERATURE SENSING SYSTEM OF ANY MANUFACTURE OR OPERATING CONCEPT!

Secondly, any draft standard – such as EN54-22 – has not been accepted by the Industry and it contains a number of anomalies …...
 It should be remembered that linear heat detection is a CONTINUOUS (not point type) detector capable of installation at point of risk (not convenient roof/ceiling height – with reliance on favourable airflows for response) and that it is capable on the majority of applications of monitoring and signalling overheat conditions BEFORE combustion is reached . Something which is impossible with point type heat detectors.

• Why therefore adopt testing principles similar to those used for point heat detectors tested to EN54-5?

• Why specify a nominal 10m sensor cable length for test when the Office of U.K. Deputy Prime minister specifies the average fire spread : direct burning as 7 sq metres?

• Why specify a test ambient temperature of 23 +/- 5C when linear detection systems are regularly installed Internationally within continuous ambients of between -40C and + 70C ( OR HIGHER)?

• Why classify Part 22 for “resettable line type heat detectors” - Reset / recovery is only possible in a laboratory when ideal conditions can be applied which ensure the destruct temperature of a pvc based cable is not exceeded. Under ACTUAL conditions, only a small % of sensor cable will be exposed – requiring a high temperature to produce the electrical resistance change. The temperature being ABOVE a level that would allow system reset without first replacement of any of the installed sensor cable.

International fire standards call for FAULT / TROUBLE indication for any open (O/C) or short circuit (S/C) condition detected. Linear heat detection of ALL operating concepts (analogue, digital, fibre optics etc) conform with those requirements.  Do not be misled because digital sensor cable short circuits under an alarm condition. This still conforms with all standards because the signalling between the sensor cable and control unit will provide  an O/C and S/C FAULT condition. Remember sensor cable is just that – a cable. Only when it is connected to an interface unit ( dedicated or switch/zone monitor, input module etc) does it become a detector. And as with point type heat detectors, their operation involves a similar internal unit S/C type operation to alarm !

 Care MUST be taken not to compare line type detectors with point type detectors when it comes to operating sensitivity and/or approvals testing.  As a continuous detector – capable of detecting at ANY and ALL points along its length- line type detectors are far more sensitive than point heat detectors and have the potential for providing far more information.      For example, Proline Factory Mutual (FM) and Underwriters Laboratories (UL) digital line type detector can provide

• Multiple channels per interface unit

• Colour coded LCD display

• Alarm Point location

• RS232 serial link – to repeat LCD messages onto customer panel or PC

• Pre-Alarm signalling

• Ambient temperature rise warning

• Site programming of a single sensor cable length to provide up to fifty (50) alarm outputs

• Continued detection with break in cable

• Full and easy  integration with ANY Central Fire Alarm Control Panel.