System Sensor BS5839 manual Intelligent Fire Alarm Systems, PRE-ALARM Facility, Fire System Zones

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Intelligent Fire Alarm Systems

1.6. DRIFT COMPENSATION AND MAINTENANCE ALARM

The sensitivity of a smoke detector tends to change as it becomes contaminated with dirt or dust (see figure 1.6.1). As contamination builds up, it usually becomes more sensitive, leading to the risk of a false alarm, but in some cases can become less sensitive, so delaying the alarm if a fire is detected. To counter this, if a detector drifts outside its specification, a maintenance signal may be sent to the panel warning that the detector needs cleaning.

To further increase the maintenance interval, many systems incorporate a “drift compensation” function, included in either the detector or the control panel algorithms. These functions use algorithms that monitor the sensitivity of a detector, and modify its response to compensate for a build up of dust in the chamber over time. Once the detector reaches the “drift limit” when the dirt build up can no longer be compensated for, a fault can be signalled. Some systems also incorporate a warning to signal that a detector is approaching its compensation limit and requires cleaning.

Threshold increased to compensate for increased chamber clean air value.

Value

 

Smoke required to

 

 

 

Chamber

 

reach alarm

 

 

threshold reduces -

 

 

 

Detector sensitivity

 

 

 

increases

 

 

 

 

 

Time

Clean Air

Uncompensated

Uncompensated

Compensated

Value

Alarm Threshold

Chamber Value

Threshold

Figure 1.6.1 Chamber Contamination and Drift

Compensation

1.7. PRE-ALARM FACILITY

use control modules to operate additional electrical equipment such as air conditioning units and door releases to prevent the spread of smoke and fire.

The alarm signals can either be a zone of conventional sounders and strobes activated via control modules on the loop or directly from the control panel, or addressable loop powered devices connected on the same loop as the detectors and activated by direct command from the panel. Loop powered sounders tend to have lower wiring costs, however the number permissible on the loop may be restricted by current limitations.

On larger sites, it may be desirable to use zoned alarms. This allows a phased evacuation to be carried out, with areas

at most immediate risk being evacuated first, then less endangered areas later.

1.9. FIRE SYSTEM ZONES

Conventional fire alarm systems group detectors into ‘zones’ for faster location of a fire, with all the detectors in a particular zone being connected on one circuit. Although intelligent systems allow the precise device that initiated an alarm to be identified, zones are still used in order to make programming the system and interpreting the location of a fire easier. The control panel will have individual fire indicators for each zone on the system, and the control panel response to an alarm is often programmed according to the zone of the device in alarm rather than its individual address.

Whilst the division of a loop into zones is achieved within the panel software, BS5839 part 1 recommends that a single wiring fault in one zone should not affect the operation

of the system in other zones of the building. To meet this recommendation, a short circuit isolator should be placed on each boundary between zones (figure 1.9.1). In this instance, a short circuit in one zone would cause the isolators on either side of the zone to open, thereby disabling that zone. Any devices in neighbouring zones would be protected by the short circuit isolators and remain operational.

One advantage of intelligent type systems is that since the data sent by a detector to the panel varies with the local environment, it can be used to detect when the device is approaching an alarm condition. This “Pre-Alarm” can be signalled at the panel and can therefore be investigated to check if there is a real fire, or if it is caused by other signals, for example steam or dust from building work. This can avoid the inconvenience and expense of evacuating a building or calling out the fire brigade unnecessarily because of a nuisance alarm. The Pre-Alarm Threshold is typically set at 80% of the alarm threshold.

1.8. FIRE ALARMS

When a fire is detected, the control panel indicates an alarm by activating the fire indicator for the relevant zone on the control panel, sending a command to the relevant detector to illuminate its LED and activate alarm signals to start evacuation. Most intelligent fire system control panels include alphanumeric displays enabling them to show information

FIRE ALARM SYSTEM OK 28 January 2003 12:15 pm

SYSTEM OK

FIRE ALARM

FAULT

SYSTEM RESET

INTELLIGENT FIRE ALARM CONTROL PANEL

ISOLATOR

Zone 1

Zone 2

ISOLATOR

Zone 3

Zone 4

ISOLATOR

on the source of the alarm. This may simply be a zone and detector address, or could be more descriptive for example “Smoke Detector, Bedroom 234”. The control panel may also

Figure 1.9.1 Intelligent System Fire Zones

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Note: This document is based on the recommendations of BS5839 Part 1: 2002. It is intended only as a guide to the application of fire detection systems.

Reference must be made to relevant national and local standards.

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Contents Guide to intelligent fire systems Guide to Intelligent Fire Alarm Systems ContentsGuide to Intelligent Fire Alarm Systems Alarm Systems Intelligent Fire Alarm SystemsIntelligent Fire Addressing Methods Decimal address switchesSystem Fault Tolerance Dedicated address programmerIntelligent Fire Alarm Systems PRE-ALARM FacilityFire System Zones Interface Modules Programming of Intelligent Fire Alarm PanelsRemote Leds Advantages of Intelligent SystemsFire System Categories GuideDetector Application Guide Category M SystemsApplication Guide Manual Call Points 1. Manual Call Point PositioningSelection of Automatic Fire Detectors Areas subject to rapid changes Fixed temperature detector 58CRate of rise heat detector During normal useDetector type Location and Spacing of Automatic Fire DetectorsCeiling Height To EN54-7 10.5m Heat detector conforming toCorridors Corridor being 7.5m and 5.3m respectivelySloping Ceilings Lantern Lights Location and Spacing of Optical Beam DetectorsVoids and False Ceilings Audible Alarm Signals Visual Alarm SignalsMaintenance of Fire Detectors Codes and standards in the UK BS5839 Part 12002, SectionIntelligent Product Range Series 200 Plus FeaturesGeneral Specifications Series 200 Plus Analogue Addressable Detector Range2251EM Photoelectric Smoke Sensor WeightSystem Sensor Intelligent Product Range 2251TEM PHOTO-THERMAL SensorDrift Compensation and Smoothing 5251REM, 5251EM and 5251HTEM Heat SensorsRemote Test Switch 6500S Beam DetectorOperating Temperature -10C to 55C Weight 142gLaser Detector With LED blink enabled 2251EIS Intrinsically Safe Detector and IST200 InterfaceB500 Series Bases Exterior diameter Weight 100gInterior diameter DepthM200 Series Module Range M200XE Short Circuit Isolator Module5A at 250VAC Specifications Max Standby Current, externally powered zoneM201E Output Module M210E-CZ Conventional Zone ModuleIndoor AccessoriesCall Points Indoor products are generally rated at IP24DSounder Strobes Audio Visual ProductsDetector Base Sounders Majority of back box formatsOther Information Avenue Hoch Paris, France Tel +33 1 53 89 00 Other InformationApproval Bodies for Fire Detection Products Jernholmen DK-2650 Hvidovre Denmark Tel +45 36 349Telephone + 7 095 Telephone + 91 124 System Sensor Fire DetectorsVolochaevskaya Str 40, Bld Fax + 7 095

BS5839 specifications

System Sensor BS5839 is a standard that pertains to fire detection and alarm systems, providing guidelines for the design, installation, and maintenance of these essential safety tools. It is crucial for safeguarding lives and property, ensuring that fire detection systems are effective and reliable. The BS5839 standard, established in the UK, covers a wide range of fire alarm system types, including conventional, addressable, and wireless systems.

One of the main features of BS5839 is its comprehensive classification of fire detection systems. The standard divides systems into categories based on the level of risk and the environment in which the system will operate. This classification helps ensure that the system installed meets the specific needs of the building and its occupants. For example, Category L systems are meant for life safety, while Category P systems are designed to protect property.

The technologies underpinning BS5839 include various types of detectors, alarm devices, and control panels. Smoke detectors, heat detectors, and multi-sensor detectors are prominent among the devices specified in the standard. Smoke detectors use photoelectric or ionization principles to detect smoke and signal an alarm, while heat detectors respond to temperature changes. Multi-sensor detectors combine both smoke and heat detection technologies to provide a more reliable response to fire conditions.

Another key characteristic of BS5839 is the emphasis on regular testing and maintenance. The standard outlines procedures to ensure that systems remain operational and effective over time. This includes routine system checks, functional testing, and more in-depth inspections at regular intervals. Ensuring that systems are maintained according to BS5839 is vital for compliance with insurance requirements and for safeguarding against potential legal liabilities.

Furthermore, BS5839 highlights the importance of staff training and awareness. It emphasizes that personnel responsible for fire safety must be adequately trained in the operation and response to fire alarm systems. This ensures that in the event of a fire, occupants are prompted to take appropriate action and evacuate safely.

In summary, System Sensor BS5839 provides a crucial framework for fire detection and alarm systems. Its classification of systems, incorporation of advanced technologies, and emphasis on maintenance all contribute to enhanced safety and compliance, protecting lives and property effectively.
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