Control and indicating equipment

The design of control and indicating equipment is a matter for the rele-vant product standard, namely BS EN 54-2,⁵² rather than for BS 5839-1.

However, the code does address three matters in relation to control and indicating equipment, namely the siting of the equipment, the facilities provided for visual indication of fire signals and the facilities provided for control of the system.

Furthermore, even if the system uses control and indicating equipment that fully complies with BS EN 54-2 (and, possibly, even third-party certificated as complying), the control and indicating equipment may, or may not, comply with at least four specific recommendations of BS 5839-1. For full compliance with the code, therefore, it will be neces-sary to ensure that these additional recommendations are satisfied.

This is an unfortunate situation, in that it is quite possible that non-compliances with the code can result from the use of control and indicating equipment that fully complies with the product standard for such equipment. This is an unfortunate quirk of the European standardization process. Although, under agreements for standardization in Europe, the UK is obliged to publish the European standard for control and indicating equipment as the national British Standard, it has, regrettably, been considered necessary to incorporate these additional recommendations in the code to ensure the appropriate level of fire safety for systems installed in the UK.

Three of these additional recommendations have already been discussed. The first concerns the integrity of the system if a cross-connection occurs between a detector circuit and a sounder circuit. As discussed in Chapter 11, the code recommends that, in the event of such a fault, only the detector circuit and sounder circuit involved should be

52 BS EN 54-2:1998, Fire detection and fire alarm systems — Control and indicating equipment.

affected; otherwise, the system should operate correctly. When control and indicating equipment is examined for compliance with BS EN 54-2, the testing or certification body would not confirm compliance with this recommendation. Moreover, it is difficult, if not impossible, to prove compliance during installation inspections. To some extent, therefore, reliance needs to be placed on information from the manufacturer of the control and indicating equipment.

The second ‘extra’ recommendation relates to the provision of zonal indicators. As discussed in Chapter 12, the code recommends that the primary indication of the area(s) from which a fire signal(s) has originated should comprise an indication of the detection zone.

Moreover, for compliance with the code, it is not satisfactory for the method of indication to comprise purely text on the normal liquid crystal or vacuum fluorescent display provided on addressable systems.

The code recommends that the form of zone indication should comprise a separate light-emitting indicator for each detection zone of the system, such that the indicating equipment is capable of simultaneous display of fire signals on every detection zone. Care should be taken by specifiers to ensure that this recommendation is satisfied, as it is considered necessary to assist those responding to a fire, particularly the fire and rescue service. However, some BS EN 54-2 compliant control panels, readily available in the UK, do not incorporate zonal indicators.

Normally, zonal indicators comprise a bank of LEDs, but could comprise an illuminated mimic diagram. Although much less likely, for compliance with this recommendation, the code would also accept a VDU provided that it could simultaneously display fire signals in all detection zones without manual intervention. In effect, therefore, the VDU could display a mimic diagram. However, because the reliability of a single VDU is not adequate, a back-up form of detection zone indication would then need to be provided for compliance with the code. This could comprise, for example, a second VDU or a printer configured to print out automatically the fire information. (A printer would not be acceptable on its own, as it, too, would not be sufficiently reliable.)

In very large premises, comprising a commensurately large number of detection zones, compliance with this recommendation could involve a very large indicator panel that would require a significant amount of space. However, in such premises, the code would accept a hierarchical system in which, for example, in the security control room for the complex, indication is limited to the sector of origin, rather than the detection zone of origin. The code defines a ‘sector’ as a subdivision of the protected premises normally containing several detection zones. It is also noted in the code that a sector may even comprise more than

Control and indicating equipment

one building. There could then be an arrangement whereby further indicating equipment within each sector indicates the detection zones.

However, as has been stressed many times in this guide, it is very important to ensure that the design of the system takes full account of the fire strategy for the building or complex. Accordingly, clause 23 of the code, which provides recommendations for control and indicating equipment, recommends that the control and indicating facilities should be suitable for the fire and evacuation procedures intended for the building. In complex premises, the code stresses the need for adequate consultation between interested parties to ensure that appropriate control and indicating facilities are provided. Therefore, in the example of a hierarchical display, it would need to be ensured that, at a central point, limitation of indications to the sector of origin would be sufficient to enable those monitoring the system at this location to have sufficient information to implement fire and evacuation procedures.

The third ‘extra’ recommendation is the restriction in the delay between operation of a manual call point and sounding of alarms within the area in question. Although BS EN 54-2 permits this to be 10 seconds, BS 5839-1 recommends a maximum of three seconds. This was discussed in Chapter 16.

Clause 23 also contains the final additional recommendation that is over and above the requirements of BS EN 54-2. The clause recommends that an evacuation control be provided. This control should be clearly labelled to indicate its function and should be provided on, or immediately adjacent to, the control equipment to enable fire alarm sounders to be started. Since this control will not necessarily be provided on control equipment complying with BS EN 54-2, for compliance with the code it would be acceptable for the control to comprise a separate device, provided it is immediately adjacent to the control equipment.

The device could comprise a manual call point, provided the manual call point was clearly labelled to distinguish its function from that of other manual call points in the building. The evacuate control may be the same as the control provided to restart sounders after silencing, as its correct operation should not be dependent on the state of any silencing or disablement device. Although the code refers to fire alarm sounders in this recommendation, it is reasonable to assert that the same facility should be provided to start any pre-recorded evacuation message in a voice alarm system.

However, in buildings with phased evacuation, no single evacuation control should result in an evacuation signal in all alarm zones simultaneously, unless the stairway capacity of the building is sufficient

to cater for simultaneous evacuation of the entire building (see also Chapter 15). Instead, a separate evacuate control should be provided for each part of the protected premises in which an evacuation signal needs to be given simultaneously.

It is necessary to restrict the operation of certain manual controls to authorized personnel. In the example of the security control room, this will normally apply, simply because access to the control room itself will be restricted.

Because the code specifically recommends zonal indication, it also recommends the provision of a zone plan on or adjacent to the indicating equipment. This could, of course, take the form of an illuminated mimic or the VDU representation described above. Otherwise, there will be a need for a correctly orientated plan of the premises, showing at least the building entrances, the main circulation areas and the division into detection zones. It should be noted that this recommendation will not be satisfied by the provision of a zone chart that simply describes the location of each zone; a correctly orientated plan is necessary. As a result of the Rosepark Care Home fire in 2004, the 2013 version of BS 5839-1 has even further increased the emphasis on the need for a zone plan (or equivalent display), even though BS 5839-1 has recommended its provision since 1988. This was as a result of the findings of the Fatal Accident Inquiry into the Rosepark fire; it was concluded that some or all of the deaths could have been prevented by the provision of a suitable zone plan.

Indicating equipment should be sited at an appropriate location for both staff and firefighters responding to a fire signal. The code suggests that this should normally be an area on the ground floor, close to the entrance of the building likely to be used by the fire and rescue service. However, an alternative is provision of indicating equipment in a continuously manned control room from, which, at least, initial control of any fire incident will be implemented. Where there are multiple entrances to a building, repeat indicating equipment might be necessary to assist the fire and rescue service. It should be noted that not all indicating equipment needs to be combined with controls that provide comprehensive control over all functions of the system. There is, however, a need for careful consideration of the fire strategy that will be adopted to ensure that the correct indicating facilities, and the correct control facilities, are provided at the appropriate locations.

The code also suggests, but does not positively recommend, that there may be benefit in locating indicating equipment at a position that will be visible to the fire and rescue service from outside the building. The philosophy here is that, if there is a facility for transmission of alarms to an alarm receiving centre, there is a possibility that the fire and

Control and indicating equipment

rescue service may attend a fire alarm signal when the premises are unoccupied. If the officer in charge can see the zonal indicators and they indicate multiple zones in alarm, it may assist him in making a judgement as to whether there really is a fire and whether it may be advisable to force entry to the premises. This was, many years ago, a traditional practice, but is very rarely adopted today.

The environment in which the control and indicating equipment is to be installed should also be considered. For example, the ambient light level must be appropriate, so that indicators can be clearly seen, controls easily operated and instructions or legends easily read.

Similarly, the noise level in the vicinity of the equipment should not be such as to prevent audible indications, such as a fault warning sounder, from being heard. Equipment that is likely to need routine attention for maintenance should be sited in readily accessible locations that facilitate safe maintenance work. It should be noted that this is not only a recommendation of the code, but is arguably necessary under relevant health and safety legislation.

The designer is also expected to consider the possible effects of fire on the control and indicating equipment. The equipment and its associated extra low voltage power supplies should be sited in areas of low fire hazard, so that the equipment is unlikely to be involved in a fire before adequate warning to occupants has been given. If the system incorporates automatic fire detection, consideration should be given to whether the areas in which any control and indicating equipment, associated power supplies and any other control facilities should be protected by automatic fire detection.

The code recommends such protection, unless the fire hazard in the area in which the equipment is installed is negligible and there is an adequate degree of fire separation between that area and areas of greater fire hazard. However, this recommendation does not apply if the area is continuously manned in the case of a Category P system, or is continuously manned when the building is occupied by any person in the case of Category L systems; in these cases, there is no benefit in the provision of automatic fire detection, since people will be present to detect a fire that might affect the equipment. Generally, these condi-tions will apply to the entrance foyer of a large building, in which it is, in any case, appropriate to install the control and indicating equipment.

There may, therefore, not be a need for automatic fire detection in this area specifically to protect the control and indicating equipment; detec-tion may, of course, be provided as part of the general fire protecdetec-tion of the building.

Special consideration needs to be given to premises in multiple occupation. For example, siting control and indicating equipment in the premises of one tenant is unlikely to be satisfactory, since the premises of this tenant might be unoccupied, making the equipment inaccessible, when other parts of the premises are occupied. The code recommends that, in premises in multiple occupation with communal parts, main control and indicating equipment should be located within a communal area, such as an entrance hall. Where no communal parts exist, the code recommends that the equipment should still be sited in an area to which access is possible at all times that the premises are generally occupied.

20. Networked systems

In recent years, the construction of large, complex buildings, such as shopping centres and multifunction entertainment complexes, has become commonplace. In these complexes, there are often several thousand automatic fire detectors. The number of detectors involved, and the distances between a central, focal point (such as a security control room) and the extremities of the complex, are such that it is often inappropriate to provide a single fire alarm control and indicating panel, to which a vast number of devices would then need to be connected via long runs of cable.

Under the above circumstances, a ‘networked system’ is commonly used. In such a system, a number of ‘sub-panels’ are distributed around the complex, and manual call points, detectors and fire alarm sounders are connected directly to these local panels. The local panels are then

‘networked’ by means of a data highway, and information from these sub-panels is relayed back to central equipment that provides the relevant degree of control and indication. The networked system may even serve a number of different buildings located on a single site.

Often there are two different ways of looking at a system that is configured in this way. First, the entire configuration of central equipment and sub-panels may be regarded as simply a single fire alarm system. If we take this view, the sub-panels are provided simply for engineering convenience. These sub-panels can then simply take the form of ‘black boxes’, with no local facilities for control or indication.

At the other extreme, one might view the configuration as a number of virtually independent fire alarm systems, each fully complying with the code. Thus, in this case, the sub-panels would incorporate all the control and indicating facilities recommended by the code and would, themselves, be sufficient to meet the specified fire safety objective, such as life safety or property protection. The purpose of the ‘networking’

may simply be to provide remote indication of alarm signals at, say, a

gatehouse, over and above the minimum system requirements necessary to satisfy the recommendations of the code.

In practice, many networked systems fall between these two extremes.

As always, however, the facilities provided, particularly at local sub-panels, need to be suitable and sufficient to support the relevant fire strategy. On the other hand, care needs to be taken to ensure that, in the event of fire, confusion does not result from operation of controls at a central point and (possibly conflicting) operation of controls at local sub-panels.

Particular care needs to be taken to ensure the relevant degree of integrity of the network itself. Commonly, examination of a networked system reveals that a data cable has been used for the network. Usually, the data cable in question is not fire resisting. In most cases, this will result in a serious non-compliance with the code, but this does depend on the way in which the system is viewed. If all sub-panels can function as ‘stand-alone’ fire alarm systems and do not depend on the network to facilitate primary alarm functions and compliance with the code, a communications failure on the network will have no significant effect.

Under these circumstances, the code treats the network as an ancillary circuit.

More commonly, the cause and effect logic for the operation of the system does depend on the network, even if only to ensure that the fire and rescue service are summoned from a central control point in the event of fire. Under these circumstances, the network forms part of the critical signal paths and should be treated in the same way as any other fire alarm circuit to which the code applies.

Where sub-panels are simply ‘black boxes’, they need not even be visible to occupants, provided they are readily accessible for maintenance purposes. For example, in this case, the sub-panels are sometimes installed within electrical risers. In such a situation, it would be disconcerting for occupants to hear audible warnings from the sub-panels (e.g. in the case of system faults that are relayed to the central equipment). Accordingly, in this situation, the code permits audible warnings to be suppressed or disabled. For example, if the sub-panel happens to comprise a panel compliance with BS EN 54-2, any internal sounder required for compliance with this product standard could be disconnected.

If the network is not simply ancillary to full compliance with the code, the communications link between sub-panels should be moni-tored, regardless of whether it comprises wiring or radio transmission.

Moreover, a fault on the communications link between sub-panels should not affect the operation of any sub-panel.

Networked systems

Also, in these circumstances, any cables used for the network should be fire resisting in accordance with the recommendations of the code (see Chapter 22). Clause 26 of the code divides fire resisting cables into two levels of performance, namely ‘standard’ and ‘enhanced’.

However, in the case of cables used for a network, standard fire resisting cables may be used in all circumstances in which the network is configured as a loop, and the incoming and outgoing sections of the loop follow diverse routings (except in the vicinity of the sub-panels), provided, also, that there will be no loss of communication to any sub-panel in the event of a single open or short circuit on the loop. It

However, in the case of cables used for a network, standard fire resisting cables may be used in all circumstances in which the network is configured as a loop, and the incoming and outgoing sections of the loop follow diverse routings (except in the vicinity of the sub-panels), provided, also, that there will be no loss of communication to any sub-panel in the event of a single open or short circuit on the loop. It