Sunday, August 31, 2008

Index – Are you Designing Fire Alarm System in Accordance with the Code?

In this series of posts, I am republishing a paper I presented in a seminar held in K.L. on 22nd July 2004.
Fire detection and alarm as passive system is the most commonly prescribed system for fire protection. The types of system available ranges from the simplest one or two point manual alert system to the most complex detection, monitoring and alarm system with interlinks to central monitoring stations and building automation and security systems.

Under current procedures on 'Certification of Completion and Compliance' (CCC), the submitting person is obligated to design and (in the final 'act of CFO certification) installed in conformity to acceptanble codes and standards. It is therefore incumbent on the submitting professional that he be proficient in technical standards and codes on which he claims to have conform with.

This series is structured into the following parts:

  1. Abstract and Introduction
  2. Overview of BS5839-1 and NFPA72
  3. Circuit Design and Survivability
  4. Appendix B – Circuits By Class and Style NFPA 72-2002
  5. Power Supply, Emergency Supply, Fail Safe Supply
  6. Cable Types, Fire Tests of Cables and Installation Practice
  7. Fire Tests – Figures 3 to 12
  8. Conclusion & Trends

Are You Designing Fire Alarm System In Accordance with the Code – 6


Trends in fire safety standards
The evolution of fire codes has seen steady and increasing sophistication in terms of practice and application. This trend is due to the increasing mass of information made available from research and forensic studies of failures and tragedies. Some trends which can be discerned can be listed as follows:

(a) Though prescriptive-based codes will still predominate in codes and standards, performance based codes will see increasing influence.

(b) Prescriptive codes will also be increasingly modified to include multiple scenario instead of simple scenario in the past. Prescriptive codes with a larger choice of scenario should not by confused with performance-based approach.

The reasons for this trend are:

(1) Harmonisation of codes (a growing international movement linked to globalisation trend) will force standards to be written on a generic basis with lee-way for multiple scenario to take into account deviations due to national conditions and practice).

(2) Increasing information and data available will enable a richer view of possible design scenarios.

(3) Increasing complexity of building projects demand more comprehensive solution.

(4) New considerations such as environmental concern and preservation of heritage are much more important issues than they use to be.

The trend above will however demand that the design or installation engineer responsible for fire safety have a higher standard of technical (and interpretation) ability. Simpler prescriptive codes of earlier times will now be more complex with higher number of parameters to contend with.

New MS1745 – Part 14 "Fire Detection and Alarm System" A working group under the supervision of Technical Committee on 'Dry Fire Protection System' is currently working towards a Malaysian Standards on Fire Detection and Alarm System. The WG has been working since 2006 and the full document be published (hopefully) in 2008. Perhaps I can get the chairman of the WG (Ir. Wong See Fong ( to write a short blog on this standard in future.

Unresolved topics It can sometimes be asserted that increasing knowledge generate more question. This can be illustrated by ongoing debate over the efficacy of fire tests currently specified in cable standards, pitching cable manufacturers and standards organisation against each other (principally European-American). It is expected that specification of fire test for cables will see the most changes in the near future.

Concluding with a caveat on unfinished issues not included
As can be noted in this presentation, other issues (e.g. voice alarm system, types of detectors, type of controllers etc) pertaining to fire alarm system are not included in this presentation. The topics covered in this paper, by itself however, shows more complexity than the Consulting Engineer (in Malaysia) would be normally aware of. It is hoped that practitioners will take note that the science of Fire Safety as a multi-disciplinary engineering science warrants more attention than currently being allocated.


(1) NFPA70:2002 "National Electrical Code";

(2) NFPA72:2002 "National Fire Alarm Code";

(3) BS5839-1 : 2002

(4) "Fire Performance of Data Communication Cables" published by the Fluoropolymer Division, Society of the Plastics Industry, Inc, Washington DC (

(5) "Fire Testing of Electrical Cables for Public Transportation" Marcelo M. Hirschler, GBH International, California.

(6) "New Developments in Fire Safety Requirements for Communication Cables in North America and Europe" 2002, Draka USA (

(7) "Highlights of the New NFPA 72-2002" in 8 parts by Dean K. Wilson, P.E.

Go back to Index

Are You Designing Fire Alarm System In Accordance with the Code – 5A

Cable types, Fire Tests of Cables, and Installation Practice

Are You Designing Fire Alarm System In Accordance with the Code – 5

Cable types, Fire Tests of Cables, and Installation Practice

Fire resistance or enhanced cables receiving increase attention. Cables are the communication pathways between components of the fire alarm system and comprise the following class:

~~Low voltage cable system, typically power supply cables to control panels (110V, 1-phase or 240V, 1-phase or 415V, 3-phase)

~~Extra low voltage (ELV) cable system, typically for data, signalling or device power-line cables at less than 50Va.c. or 110Vd.c.

With the notion of linking issues of fire safety and circuit integrity or survivability, fire rating of cables are now receiving increasing attention from both codes. Both codes though not providing detail explanation of fire ratings, cross-referenced other codes which have relevance to fire rating of cables. Information on fire rating of cables and the specification of fire rated cables bear some difference in opinion between the European standards (which is also the IEC standards) and the North American ANSI/UL standards. This section will include an explanation of fire rating of cables which are not found within BS5839-1 and NFPA72 themselves.

BS5839-1; prescription for cables
The 2002 edition of BS5839-1 contains major upgrade to the 1988 edition by recommending fire resistant cables. Fire resistant cables are now extended to include two types (1) Enhanced and (2) Standard. The following recommendations are included as follows:

~~Clause 26 now specify that all cables must comply with existing requirements of BS6387, EN50200 PH30 (standard) or EN50200 PH120 (enhanced).

~~All system cables including LV mains supply to the panel to be fire resistant.

~~Standard fire resistant cables should be considered sufficient to meet the effects of fire with suitable jointing and support.

~~Enhanced cables are recommended in:

(1) Non-sprinkler buildings with more than four phases of evacuation.

(2) Non-sprinkler buildings of greater than 30 metres in height.

(3) Where the critical interlinking paths might be affected in unsprinklered linked buildings with occupancy requiring supervised evacuation or some difficulty in evacuation e.g. hospital.

Notes: In case (3) above, standard cables may be used if network loops provide the 'interlink' and such loops have start and return routed separately. In such case, the network loop is said to declassify the interlink as 'critical' .

(4) Where following risk assessment enhanced cables are deemed necessary.

~~Cable support system shall match the fire rating and performance of the cables. In practice this may require examination of plastic ties, trunking or clips which may act as critical components of the support system and which may not be suitably fire rated.

~~No external joints shall be used. Where junction boxes are not avoided, they shall be labelled "Fire Alarm" and match fire resistance rating of the cables.

~~Standard cables installed below 2m height require mechanical protection unless surface clipped to strong construction in relatively benign environments e.g. offices shops etc.

~~All conductors should have minimum cross sectional area of at least 1mm² and if stranded a minimum cross sectional area of 0.5mm².

~~Segregation of wirings:

(1) fire alarms should be segregated from other services in separate conduit or trunking.

(2) Where multicore cables are used none of the other cores should be used for other purposes.

(3) Mains cables should be segregated from system cables outside and inside the panel. They should not enter the panel at the same point.

~~Fire cables should be a single common colour throughout a building to aid identification, e.g. red. Figure 3 – Fire Rated Cables to BS5839-1 2002 .

Fire rating of cables in NFPA72 is cross referenced to NFPA70 (NEC)
In NFPA72 only two paragraphs described wiring requirements with a cross-reference to NFPA70 (National Electrical Code). This cross referencing however opens a wide topic related to cable types and fire performance rating based on North American (NFPA, UL and ANSI) standards. The following tabulation list Articles in NFPA70 (NEC) which are relevant.

Table 1 – Cable types and Fire Tests (North American)

Article 760 – Fire Protection Signalling System


Fire Test


Power limited fire alarm cable for general purpose fire alarm use.

UL 1581 Vertical Tray Flame Test


Power limited fire alarm riser cable for use in vertical riser shafts

UL 1666 Riser Flame Test


Power limited fire alarm plenum cable for use in ducts and air plenums

UL 910 Steiner Tunnel Test

Article 770 – Optical Fiber Cables and Raceways


Non conductive and conductive optical fiber plenum cables suitable for use in ducts, plenums and other environmental air spaces.


Non conductive and conductive optical fiber riser cables plenum suitable for use in vertical run in shaft or from floor to floor


Non conductive and conductive optical fiber cables suitable for general purpose use except in vertical risers and plenums.


Non conductive and conductive optical fiber cables suitable for general purpose use except in vertical risers, plenums and spaces used in environmental air.

Article 800 – Communications Cables and Raceways


Communication plenum cable listed as being suitable for use in ducts, plenums and other spaces for environmental air


Communication riser cable listed as being suitable for use in vertical run in shaft or from floor to floor


General purpose communication riser cable listed as being suitable for general purpose use except in vertical risers and plenums.


Communication cable listed as being suitable for use suitable for general purpose use except in vertical risers and plenums.


Limited use communication cable suitable for use in dwellings and raceways


Undercarpet communication cables suitable for undercarpet use

Note: CSA C22.2 No. 0.3M (Canadian Standard Association) defines resistance to the spread of fire is for the damage (char length) not to exceed 1.5 m (4 ft 11 in.) when performing the vertical flame test for cables in cable trays.

Details pertaining to segregation of cables similar to BS4839-1 (section 5.2) and measures for the mechanical protection of cables are included in NFPA70. Articles 760, 770 and 800 however contain more details pertaining to such installation measures compared to BS5839-1.

Fire Tests to European / British Standards

An understanding of fire tests on cables is essential before designers and installers can select the correct type of cables in compliance with the code. As British Codes and Standards are harmonising towards European Codes (EN), a description of the fire test for EN and BS can be taken to be similar. Table 2 describes the test listed under the hierarchy cables specified under BS5839-1.

Table 2 – List of Fire Tests under British Standards

BS6387:1994 CWZ

Fire Resistance, with and without water and mechanical shock; Specification for performance requirement for cables required to maintain circuit integrity under fire conditions:

Cat. C Exposed to Fire @ 950ºC. for 3 hours

Cat. W

(1) Expose to fire @ 650ºC for 15 mins., then

(2) Expose to fire @ 650ºC with water for 15mins.

Cat. Z

(1) Expose to fire @ 650ºC for 15mins., then

(2) expose to fire @ 650ºC. with mechanical shock for 15mins.

EN50200 BS5839-1:2002 Fire Performance Cable
Standard Grade BS5839-1:2002 - PH 30

PH30 (30 mins)

(1) Exposed to fire @ 830ºC. for 15mins., then

(2) exposed to fire @ 830ºC. with water & mechanical Shock for 15mins.

The temperature may vary +40 / - 0 deg. C

(Test No 2. is not detailed within EN50200 PH30 but is covered in BS5839-1:2002, Clause 26.2-D)

Enhanced Grade BS5839-1:2002 - PH 30

PH120 (2 hours)

(1) Exposed to fire @ 950ºC. for 60mins., then

(2) exposed to fire @ 950ºC. with water & mechanical Shock for 60mins.

The temperature may vary +40 / - 0 deg. C (Test No 2. is not detailed within EN50200PH120 but is covered in BS5839-1:2002, Clause 26.2-E)

BS7629-1 BS7629-1 E1 BS7629-1 E2

Specification for 300/500V Fire Resistant Electric Cables.; Having low emissions of smoke and corrosive gasses when effected by fire (Multi Core Cables)

BS4066-1-15.5, Cat. S

Fire Performance; Test on Electric Cables Under fire Conditions

BS7622 Cat.S Replaced By BSEN50268-2:2000 BSEN50268-1:2000

Smoke Emissions; Common test methods for cables under fire conditions, Measurement of smoke density of electric cables burning under defined conditions.

BS 6387 Tests by fire, water and mechanical shock. This test is used to determine capability of cables to maintain circuit integrity under fire conditions. Additional conditions of water and mechanical shock are applied for grading of capability of cables. Code used to designate capability of the cables are as follows:

Resistance to fire


650ºC for 3 hours


750ºC for 3 hours


950ºC for 3 hours


950ºC for 20 minutes


Resistance to fire & water


650ºC for 15mins. then for 15min with fire and water


Resistance to fire with mech. shock


650ºC for 15mins. with 30 seconds hammer blow


750ºC for 15mins. with 30 seconds hammer blow


850ºC for 15mins. with 30 seconds hammer blow


Figure 4 – Fire Resistant Test; Figure 5 – Resistance to Fire and Water; Figure 6 – Resistance to Fire and Hammer Blows;

IEC 60331 Fire Tests This test is used to determine whether a cables can maintain circuit integrity during and after exposure to fire.

A sample of cable is exposed to fire for 3 hours at a temperature of between 750ºC and 800ºC while energised. After 3 hours the fire is extinguish and the circuit turned off. A duration of 12 hours is allowed before re-energising the cable and checking for circuit integrity.

IEC 60332-3 – Flame Propagation Tests
This test defines the ability of bunch cables to restrict flame propagation when laid in trunking, cable trays or conduit. The tests comprises 3 categories each determined by the amount of combustible material in a 1 m sample.





Litres of combustible material in a 1 metre sample




Exposure to fire in minutes




The cable sample are placed vertically next to one another on a vertical tray where they are exposed to fire from a ribbon gas for the duration of exposure. After burning, the samples are wiped clean to examine for char on the surface of the cable. Charring should not reach a height exceeding 2.5m above the bottom edge of the burner. Figure 7 IEC 60332-3 Flame Propagation Test

IEC 61304 Smoke Density Test
This test measures the smoke emission from cables during a controlled fire. The test sample is burn in a chamber measuring 3m cubed The amount of smoke emission is measured by a light beam-photocell which measures the opacity of the smoke.
Figure 8 – Smoke Density Measurements

North American Standards on Fire Tests

The main fire tests recognised by the North Americas are the following:

  • UL VW1 – Single Cable Burner test

  • UL 1581 Vertical Tray Flame Test
  • UL 1666 Riser Flame Test
  • NFPA262, UL910 Steiner Tunnel Test

UP VW1 test on a single cable. This is the lowest grade test for assessing the fire resistant ability of a single cable. It is also similar to IEC 60332-1. It applies a flame (500W) to a single vertical cable sample and assess flame spread capacity (pass or fail criteria).

UL 1581 Vertical Tray Flame Test This test is similar to the IEC60332- part 3 test for group of cables (Figure 9 – UL 1581 Vertical Tray Flame Test (CM rating))

The flame load is a 30kW burner with the vertical samples free standing (compared to IEC60332-3 which is installed against a wall). Optional smoke density measurements may also be made.

UL 1666 Riser Flame Test
This test address the need to assess fire performance for cables grouped in risers. In UL1666, cables are mounted in a vertical tray arrangement within a 19ft high concrete shaft divided into two compartments at the 12 ft level and with 1ft by 2ft opening between compartments (to mimic a cable riser). The ignition source is a gas flame of 155kW which is left to burn for 30 minutes. Cables pass the test if no "flame" appear at the top of the bottom compartment during the test. Char length and smoke obscuration, mass loss or heat release may (or may not) be measured. Results are based on flame height
Figure 10 – UL 1666 Riser Flame Test (CMR Rating)

150kW burner tested for 30 mins. for cables grouped on vertical tray in a riser shaft 19' high with bottom compartment 12' high. Criteria for passing test is the absence of flame at the bottom of top compartment during fire test.

NFPA262 or UL910 Steiner Tunnel Test
is most the stringent test for plenum cables. Test samples of cables grouped are loaded into a horizontal tunnel 25ft long by 1 ft wide (Steiner Tunnel). A gas flame of about 88kW is applied for 20 minutes under a 240 ft/min air flow rate. Flame spread distance along the cables (from flame origin) and smoke optical density at the exhaust duct of the tunnel are measured. Cables are certified acceptable when flame spread is less than 5ft from flame origin and optical smoke density do not exceed 0.5 peak and 0.15 average.
Figure 11 – UL910 or NFPA262, Steiner Tunnel

Cables certified under 'Steiner Tunnel' test are said to be fire resistant with low smoke characteristics and are suitable for use in plenums (space where services pipes and ducts are routed e.g. space above false ceiling).

Hierarchy of Fire Tests

A hierarchy of fire test as illustrated in Figure 4 above shows the fire performance rating rank by fire test.
Figure 12 – Hierarchy of Fire Performance Tests

Note: BRE/FRS refers to the "Building Research Establishment/ Fire Research Station" at Bedford, England who set up full scale or scaled test rigs.

Next --> Figures; of Fire Tests

(1) Abstract and Introduction
(2) Overview of BS5839-1 and NFPA72
(3) Circuit Design and Survivability
(4) Appendix B – Circuits By Class and Style NFPA 72-2002
(5) Power Supply, Emergency Supply, Fail Safe Supply
(6) Cable Types, Fire Tests of Cables and Installation Practice
(7) Fire Test -Figure2 3 t0 12
(8) Conclusion & Trends

Are You Designing Fire Alarm System In Accordance with the Code – 4

Power Supply, Emergency Supply, Fail Safe Supply

Principles of reliability of power supply and similarity between both codes. Power supply for fire protection systems under both codes contain similar principles of ensuring reliability of power supplies. Primary supply source which are unreliable should not affect the operation during normal operation and response during fire conditions. Both codes advocate the backing up of primary (or main source) power supply with a standby supply with or without generator back-up.

Power supply prescribed in BS5839-1 can be summarised as follows:

Primary power connection:

~~Cables/apparatus directly connected to a public or private distribution supply should be in accordance with IEE Wiring Regulations (BS7671).

~~ Connection to the mains supply should be via an isolating protective device (e.g. isolating switch-fuse) reserved solely for the purpose. Isolating device should be suitably labelled with warning (in red) and may be enclosed in secure box to prevent unauthorised access.

~~The design of the system should ensure that residual current devices (RCD) are not necessary. In cases where RCD is unavoidable, interruption of the general building supply in response to a fault should not result in interruption of the fire alarm supply.

~~Continuity of supply to fire alarm system should be ensured.

~~Switching off supply due to reasons of maintenance, emergency, energy savings etc should not affect power to (except in unoccupied premises with a simple manual system).

~~In distributed power supply system, failure or disconnection of the supply to any individual unit should be indicated at the main indicator panel as a fault. Any switch that can disconnect the power supplies to all or part of the system should be suitably labelled with warning and coloured red.

Types of power supply

~~Normal supply should be derived from the public supply system, transformed or modified Where no public supply system is available, privately generated power may be used.

~~Standby Supplies comprise secondary batteries or secondary batteries augmented with standby generators.

Maximum alarm loads is defined as the maximum load imposed by the alarm system under fire conditions. It include the power required to operate sounders, detectors, fault warning and illumination of monitoring devices and all ancillary services powered by the fire alarm system.

Standby Supply Generally standby supply are as follows:

~~Comprises of a rechargeable battery and automatic charger. The battery should have an expected life of 4 years. Car batteries are not to be used.

~~The batteries should be labelled with their date of installation. Battery should charge up from its final voltage in 24Hrs.

~~For category M and L systems the battery should be able to support the system for 24hrs and then sound the alarm for 30 mins. If a back up generator is used the battery should be able to support the system for 6hrs and then sound the alarm for 30 mins.

~~For category P the 24 hrs plus half an hour ring applies a) providing the building is 'supervised' (staff monitoring at 6 hours interval) or b) power failures are automatically notified to a remote station for response from supervisor.

~~For category P the battery should support the system for 24 hrs longer than the building is unoccupied up to 72 hrs whichever is the less, plus half an hour ringing whatever applies. If the building is ever unoccupied for longer than the standby battery time and there is facility for remote transmission then the power fault should be remotely transmitted.

Power supply in NFPA72
can be summarised in the following terms:

Power source:

~~Fire alarm system shall be provided with at least two independent source of power supplies; one primary and the other secondary (standby).

~~Exceptions to above; when the primary source is supplied by a dedicated branch circuit of an emergency supply system or a legally required or optional standby system.

Notes: NFPA70 or the 'National Electrical Code' (NEC); Articles 700 defines Emergency Supply System as essentially for emergency loads (load during emergency condition); Article 701 Legally Required Standby System is a subset of Article 700 system but restricted for legally required load (communications, legal utilities etc), and Article 702 defines Optional Standby System for loads which may contribute to life safety but are not within the purview of legally sanctioned standby loads.

Primary Supply

~~Primary supply shall have high degree of reliability and may be either i) a light & power service (i.e. normal mains supply), or ii) an engine-generator set provided such generator are fully supervised by trained operator.

~~Connections to 'light & power' service shall be from dedicated branch circuits. Circuit should be mechanically protected. Circuit disconnector should red-marked, prominently labelled and accessible only to authorised personnel.

~~Overcurrent protection devices to protect against short circuit in ungrounded conductor shall be provided.

Notes: Overcurrent protection against short circuit protection will normally perrtain to fine-protection class fuses (IEC standard). Depending on the location of the circuit and prospective short circuit current, Miniature Circuit Breaker (MCB) may not be capable of interrupting short circuits above 6kA. However, this condition principally relates to the North American centre-tap 110/220V system which may produce higher short circuit currents compared to the IEC defined TN-S system which would be the norm for final circuit for power outlets in Malaysia.

Secondary Supply The secondary supply shall automatically supply energy to the system within 30 seconds, without loss of signal, whenever the primary supply system fails.

The secondary supply system shall have sufficient capacity to operate:

  • 24 hours the complete system under maximum quiescent conditions;
  • and then be capable of operating 15 minutes of full evacuation alarm operation at maximum connected load.

Secondary supply for emergency voice alarm communication system shall similarly operate 24 hours under quiescent conditions and shall be capable of operating the system for 2 hours during emergency conditions.

The secondary supply may consist of

  • storage battery system, or
  • standby generator system augmented with storage battery of 4 hours capacity (duration to power the fire alarm system).

Continuity of Power Supply
pertains to all cases of power transfer between primary and secondary source and can also be taken to cover power source connected from emergency or standby system. Continuity of supply must be maintained as follows:

~~power transfer must be automatic and generator must start up within 30 seconds;

~~standby batteries shall be maintain continuity of supply and to provide 15 mins. of power supply to the alarm system and to computer UPS forming part of the fire alarm system.

Next à Cable Types

(1) Abstract and Introduction

(2) Overview of BS5839-1 and NFPA72

(3) Circuit Design and Survivability

(4) Appendix B – Circuits By Class and Style NFPA 72-2002

(5) Power Supply, Emergency Supply, Fail Safe Supply

(6) Cable Types, Fire Tests of Cables and Installation Practice

(7) Fire Test -Figure2 3 t0 12

(8) Conclusion & Trends

Are You Designing Fire Alarm System In Accordance with the Code – 3 Appendix B

Appendix B -Circuit By Class and Style, NFPA 2002

Are You Designing Fire Alarm System In Accordance with the Code – 3?

Circuit Design and Survivability
The integrity or survivability of fire alarm circuits.
As noted in the previous section, the need to maintain circuit integrity (BS5839-1) or circuit survivability (NFPA72) shares commonality in concept and ideas which are receiving increasing attention in both codes. The idea of circuit integrity or survivability arises from the understanding that fire can develop before it is registered by the detectors and/or alarm raised. The interval between the start of a fire and its putative detection may very well damage components of the alarm system thereby increasing the response time to its discovery and eventual intervention by fire officers. Such scenario is increasingly a possibility due to the complexity of buildings and its internal space planning.

Circuit integrity in BS5839-1 is defined in prescriptive terms which can be summarised as follows:
Circuits containing detectors
~A fault, or faults, in one zone cannot prevent the operation of the system in other zones of the building.
~A single fault should not remove protection from an area greater than that allowed for a single zone (which has a maximum area of 2,000m²).
~Two simultaneous faults should not remove protection from an area greater than 10,000 m².
~Removal of detectors or call point from the circuit should cause indication of fault signals for immediate intervention by officers.
~Detectors designed to be removable from their bases should not affect the operation of manual call points.
~Malicious removal may be considered by the inclusion of lockable device with special tools for removal of detectors.
~The system should be designed to minimise disruption during maintenance and testing. It is desirable that provision be made allowing individual detectors to be tested without the need to sound an alarm or to disable the particular circuit.
~Isolation of all detectors or call points in single zone system is permissible but facility retained for allowing activation of general alarm from the control panel.
~Provision for isolation of detectors or call points for maintenance or testing should be such as to allow the operation of alarm sounders in response to the operation of detectors or call points that have not been isolated.
Circuits containing fire alarm sounders
~If alarm sounders are connected to the same wiring as detectors, then no alarm sounder should be affected by the removal of any detector.
~Any sounder that is necessary in order to reach the recommended audibility levels (65dB or 5dB above ambient noise level or 75dB in case of premises with sleeping resident) should only be removable or electrically disconnected from the sounder circuit by the use of a special tool and the disconnection should generate a fault warning at the control and indicating equipment.
Devices which are connected in a ring (usually though not always for addressable systems)
~Provided that the devices can receive or send signals in either direction, they will continue to operate even with a single circuit or high series resistance in the ring. Such faults should be indicated at the control and indicating equipment within 60 min of their occurrence.
~Short circuit on simple ring circuit (which cannot offer protection against such fault), should be indicated, without giving a false alarm of fire, within 100 s.
~Where sounders are used in simple ring circuits, the distribution wiring to each sounder circuit should be protected against overload due to short circuit by a fuse or similar device.
~Short circuit isolating devices are recommended for protection against cable faults in ring systems, where such device will isolate short circuit to sections of the circuit without affecting the whole circuit.
In most case, implementing measures to comply with the above requirement involve physical configuration of hard wiring and/or hardware which have to be addressed during design stage. Some examples are as follows:
~~Physical segregation of circuits between zone.
~~All sounders to be physically hardwired separately from detector circuits.
~~In case of ring circuit (usually though not limited to addressable system circuited in a loop), the above two measures may have to be adopted (i.e. physical segregation of circuits) despite the ability of addressable circuits to accommodate individual devices in a loop.
~~Alternatively short circuit isolating devices (either inbuilt into initiating or notification devices or installed discretely onto segments of the ring) may be used to demarcate segment of the ring to comply with the above requirements.
~~In a ring circuit, the start and return leg of the loop are physically routed separately.
~~Physical configuration of control panel, devices and circuits allow for fault indication in case of short circuit and removal of devices from the circuit (similar to class A and B circuit under NFPA72 and illustrated in Figures 1 and 2 below).
Class and style of circuit in NFPA72 as defined carries similar notion of circuit integrity as in BS5839-1.
Class Circuits are designated class A or B depending on its capability to transmit alarm and trouble signals during non-simultaneous single circuit fault conditions:
~Class A circuits are capable of transmitting an alarm signal during a single open or a non-simultaneous single ground fault.
~Class B circuits are incapable of transmitting an alarm beyond the location of the fault conditions specified for class A.
Style for initiating devices, notification appliances and signalling line circuits describe requirements in addition to the requirements for Class A and B circuits. Styles are designated for the various circuits depending on its ability to meet alarm and trouble performance during a single open, single ground, wire-to-wire short and loss-of-carrier fault condition.
~Initiating device circuit shall be Style A, B, C, D or E (table 1 in Appendix B);
~Notification appliance circuit shall be Style W, X, Y or Z (table 2 in Appendix B).
~Signalling line circuit shall be Style 0.5, 1, 2, 3, 3.5, 4, 4.5, 5, 6 or 7 (table 3 in Appendix B).
Further conditions on circuits prescribed can be summarised as follows:
~All styles of Class A circuits (except wireless circuits) shall be installed with outgoing and incoming conductors physically routed separately.
~Exceptions to above (separation of incoming and outgoing) are when:
distance of loop do not exceed 10ft (3m);

vertically run conductors are enclosed in 2-hour rated cable assembly or enclosure;
~~ in looped conduit/raceway single drop to individual devices is permitted;
~~ in looped conduit/raceway single conduit or raceway drops or tap-outs to multiple devices within a single room not exceeding 1,000ft² (92.9m²) in area shall be permitted.
Tables in Appendix B illustrates implementation of circuit by style.

Next Appendix B
(1) Abstract and Introduction
(2) Overview of BS5839-1 and NFPA72
(3) Circuit Design and Survivability
(4) Appendix B – Circuits By Class and Style NFPA 72-2002
(5) Power Supply, Emergency Supply, Fail Safe Supply
(6) Cable Types, Fire Tests of Cables and Installation Practice

(7) Fire Test -Figure2 3 t0 12
(8) Conclusion & Trends

Are You Designing Fire Alarm System In Accordance with the Code – 2?

BS5839–1 and NFPA72 – A Overview

Scope of BS 5839-1 and NFPA 72
In ensuring that reasonable care and due diligence have been taken in the design of fire detection and alarm system, compliance to technical standards is a key test. Two standards of which Malaysian engineers are most familiar are BS5839 and NFPA 72.

BS5839 "Fire Detection and Alarm Systems for Building" comprise 8 parts. British Standards (similar to ISO standards) are structured into parts with each part containing particular aspect of the standard or code. Each part is self-contained within its own right and as can be seen from a listing of all parts of BS5839, Part 1 "code of practice for system design, installation, commissioning and maintenance" will be the code consulted by design engineers.

* Part 1-:-2002 – Code of practice for system design, installation, commissioning and maintenance.

* Part 2-:-1983 – Specification for manual call points (withdrawn and replaced by BS EN54-11:2002)

* Part 3-:-1988 – Specification for automatic release mechanisms for certain fire protection equipment

* Part 4-:-1988 – Specification for control and indicating equipment (withdrawn and replaced by BS EN54-2 'Control and indicating equipment' and BS EN54-4 'Power supply equipment').

* Part 5-:-1988 – Specification for optical beam smoke detectors.

* Part 6-:-1995 – Code of practice for the design and installation of fire detection and alarm systems in dwellings.

* Part 8-:-1998 – Code of practice for the design, installation and servicing of voice alarm system.

* Part 9-:-2003 – Code of practice for the design, installation, commissioning and maintenance of emergency voice communication systems.

NFPA 72 "National Fire Alarm Code" published by the National Fire Protection Association of North America, in contrast to BS5839 is published as one self-contained book (as is the normal structure of NFPA standards). NFPA72 is styled as a manual but worded as a legal document. It is organised into chapters with 'Articles' within each chapter. The 2002 edition reorganised the chapters of the previous (1999) edition as follows:

* Chapter 1 – Scope and purpose;

* Chapter-2-–-Referenced publications (previously chapter 9);

* Chapter-3 – Definitions (previously contained in chapter 1);

* Chapter-4-– Fundamentals of Fire Alarm Systems (previously contained in chapter 1);

* Chapter-5-– Initiating devices (previously chapter 2);

* Chapter-6-– Protected premises fire alarm systems (previously chapter 3);

* Chapter-7-– Notification appliances for fire alarm systems (previously chapter 4);

* Chapter-8-– Supervising station fire alarm systems (previously chapter 5);

* Chapter-9-– Public Fire Alarm Reporting Systems (previously chapter 6);

* Chapter-10-– Inspection, testing, and maintenance (previously chapter 7);

* Chapter-11-– Single- and multiple-station alarms and household fire alarm systems (previously titled 'Fire warning equipment for dwelling units in chapter 8).

* Annexes (previously called Appendixes) are described as 'not part of the code' but provided for information purposes only. Three annexes are included as follows:

~ Annex A – Explanatory Materials (this annex contains much of the material pertaining to detail interpretation on locating/spacing of detectors, circuiting of devices based on class and style etc);

~ Annex B – Engineering Guide for automatic fire detector spacing (provides a 'performance-basis' for the location and spacing of heat detectors with formulas and data on heat release rate for common building materials included).

~Annex C – Referenced publications.

Types of Alarm System Detection and alarm system prescribed ranges from the simplest one or two point manual alert system to the most complex detection, monitoring and alarm system with interlinks to central monitoring stations, building automation and security systems. An understanding of the type of system possible or prescribed in BS5829 and NFPA72 is essential before an in-depth description on wiring practice and power supplies can proceed.

BS5839-1 approaches system design by defining fire protection needs based on categories of protection as follows:

*Type P – Protection of Properties

P1 – All areas covered with detectors except voids less than 800mm in height

P2 – Defined areas in a building having a high fire risk.

*Type L – Protection of Life

L1 – Same as P1

L2 - Same as P2 but for areas with high fire risk to life

L3 – Protection of escape routes

L4 – Protection of circulation areas (2002 edition)

L5 – Fire engineered solution to meet criteria of fire safety & protection of properties (2002 edition).

*Type M – Manual System

*Suffix X – System with multi-occupancy use.

BS5839-1 do not specify the type of system to be used but prescribes consultation with interested parties such as the authorities, property owner, insurance company and others. Factors which may determined the choice of system type include consideration for life and business risk, legal requirements, insurers requirements, maintainability etc. Appendix A (extracted from Annex A of Standard illustrate range of current custom and practice.

NFPA72 do not specify the type of system to be used (manual or automatic detection and at which location etc) but merely specifies the performance criteria, design features, installation method and maintenance procedure for fire alarm system. NFPA 72 recognises that consideration for active and/or passive fire protection system should be integrated as a 'life safety plan' which take into account other aspect of fire safety such as prevention, egress, protection and particular aspects of occupancy. NFPA 101 'Life Safety Code' contains detail prescriptions on the type of systems recommended for the various types of occupancies. In keeping with the 'manual style' format of NFPA72; fire alarm systems are classified as:
* Household fire warning systems;

* Protected premises for fire alarm systems (this class of fire alarm include most systems designed for apartments, offices, industrial buildings etc.);

* Supervising station for fire alarm system (this include specification for communications between alarm system and supervisory station which may be local, remote or municipal master fire alarm panel).

A Comparison of BS5839 and NFPA72 shows the major difference or similarity in style and content of both codes:
Structure of Code BS5839 is structured into parts each of which self-contained within its own rights. NFPA72 is written in a comprehensive manner with chapters containing all aspect of fire alarm system.

Revision Cycle Editions for both codes showing revision cycles are as follows:
~ BS5839-1 1980, 1984, 1988 and 2002
~ NFPA72 1990, 1993, 1996, 1999, 2002

Scope Both BS5839 and NFPA do not specify the type of system for the various types of occupancies or premise. BS5839 recommends consultation with interested parties (authorities, owner, insurer etc) whilst NFPA72 specifically refers to NFPA101 'Life Safety Code' for prescription on the type of systems to be installed for various occupancies. Thus both codes limit themselves purely to a specification on the design features, installation aspect and maintenance procedures for fire alarm system,

Coverage Due to the structure of BS5839, part 1 by itself however do not contain detail specifications for components of fire alarm system (such as detectors, manual call points etc.), voice alarm, emergency voice communication system and small alarm system in dwellings as they are covered in other parts of BS5839. or other BS (BS EN54). NFPA72 in comparison include all scope not included in BS5839-1 (refer section 2.1 above). BS5839 taken as a whole (i.e. including all parts) however can be said to be similar in scope and coverage of NFPA72.

Language Style BS5839 is written generally in the format of a 'guide' with 'recommendations' setting out performance requirements whilst NFPA72 is written in the style of a manual. The manual style of NFPA72 contains detail installation and design guide whilst BS5839 is a little sketchy on details.

Details BS5839 has less details on installation and design issues keeping instead to setting broad criteria of design whilst NFPA72 is full of details pertaining to design and installation, example:
~ BS5839-1 recommendations on circuit "survivability" are brief clauses such as "a fault on one zone shall not prevent the operation of the system in other zones..." or "A single fault shall not remove protection from an area greater than that allowed under 7.2(a) ..." etc. Designers and installers of alarm system are presumably left to decide on system hardware and wiring to comply with the above.
~ In comparison NFPA72 defines circuit "survivability" in terms of circuit class and/or style. The class and style designation contain details which specifically prescribe how hardware and circuits should be configured .

Fire Zones
Both BS5839-1 and NFPA72 contain similar concepts of fire zone with minor differences mainly on the system of units. Maximum area for one fire zone is specified as 2,000m² for BS5839-1 and 20,000ft² (or 1,860m²) for NFPA 72.

Classification of System Types BS5839 classifies system types based on fire protection needs; type P for protection of properties, type L for protection of life and type M for manual system. In BS5839-1, the types of system determines system configuration (detectors coverage, manual call points etc). NFPA72 do not have such a classification concept similar to BS5839-1 but instead rely on NFPA101 to determine fire needs for system configuration. Section 2.2 has details of system types.

Spacing of initiating devices The location and spacing of initiating devices (heat/smoke detectors) is prescribed as follows:

~BS5839-1 is specific on spacing as follows:

smoke detectors under flat ceiling – 7.5m

heat detectors under flat ceiling – 5.3m

in corridor under 2m wide detector spacing may be 15m (smoke) and 10.6 (heat);

detector density may be generally calculated at 100m² (smoke) and 50m² (heat);

On pitched roofs with detectors at or near the apex distances increase by 1% for each degree of slope to a maximum of 25%.

manual call points are recommended at 30m travel distance.

~NFPA72 has a performance oriented approach with regards to detectors spacing:

No exact figures are prescribed but detector spacing should be based on 'listed' spacing.

A figure of 30 ft (9.1m) is quoted as a guide for spot type smoke detectors but with caveat on complying with manufacturer's instructions.

Correction factors to 'theoretical' spacing (i.e. listed or manufacturer's recommendations), include consideration for pitch roof, ceiling heights, corridors etc. which are listed in great details (especially in Annex A).

Location of additional manual call points are recommended at 200ft (61m) travel distance (compare with BS5839-1 prescription of 30m).

Listed is defined in NFPA "included in a list published by an organisation that is acceptable to the authorities having jurisdiction and concerned with evaluation of products or services ...". Examples of a listing organisation is "UL".
Circuit Design again illustrate the difference between the depth of details contained in BS5839-1 and NFPA72.
~BS5839-1 contains general recommendations for "circuit integrity" which are performance oriented in aspect.
~NFPA in contrast though also containing requirements for "circuit survivability" similar in nature to BS5839-1 include detail classification of circuit 'class' and 'style'.
Power supply Both codes similarly prescribed secondary or standby supplies using batteries with or without generator backup. Differences relates to interpretation of 'operational time' (which is the operation time required after basic 24 hours quiescent operational capacity):
~Under BS5839-1, operation time is generally interpreted as 30 minutes of maximum alarm loads (i.e. all sounders ringing) during fire conditions;
~NFPA72 defines operation time as 15 minutes of maximum load during fire conditions (i.e. with sounders ringing).
Cables and Wiring Requirement Both codes similarly prescribed fire rated or 'enhanced' cables with differences in defining performance ratings for 'enhanced' or fire rated cables. The definition of fire-rating between the British (and by extension European and IEC) standards and the NFPA (north American and ANSI) standards has differences which will be described in greater details in section 5.

~ The 2002 edition of BS5839-1 contain major enhancement to the recommendations on use of 'standard', 'fire-rated' and enhanced cables. Other BS codes are referenced in defining standard tests for enhanced or standard cables.

~ NFPA72 contain only a brief reference to cabling requirement. The brief referral however point to NFPA70 ('National Electrical Code') Articles 760, 770 and 800.

Other Major Differences or Similarities between the two codes include the following:

~ The 2002 edition of BS5836 include major enhancement with new subjects some of which are not included in NFPA72:

A new section address issues of false alarm by defining false alarm and steps to mitigate such false alarms (no equivalent in NFPA72).

Additions to section 6 (maintenance) champions the concept of continuous monitoring of system functions (a useful concept where legislative measures for re-certification or regular certification of premise is to be enforced) (no equivalent in NFPA72).

Performance based design is given due recognition with addition of new system type L5 ('engineered solution'). A new BS document PD 7974-4 "Fire safety engineering principles in building; part 4 – detection of fire and activation of fire protection system" (2003) contains guidance on development, design and application of performance based solutions for fire alarm system. (NFPA72 already contain substantial information on this subject as annex).

~ NFPA72, since the 1999 edition include substantial information material for designing to 'performance-based' criteria.

Next àCircuit Design & Survivability

1) Abstract and Introduction