星空传媒

The large, centralised, retail outlets that have been translated across the Atlantic from America have created a unique problem. The conundrum is how to install a composite landlord (public areas) and tenant (individual retail outlets) fire alarm system, where the landlord hosts a system into which each retail outlet has its own system linked. In such a set-up each tenant is responsible for covering the fire risk within its own area.

In many other commercial premises where a landlord with tenants exists, the fire alarm is supported by the landlord on behalf of the site, without the need for each tenant to support separate alarms.

The main technical difficulty with the new set-up is the two-way control between the systems, especially if different technologies are being used.

Reduced loop loading, simplified programming and the minimising of unwanted alarms are just some of the benefits accruing from a considered re-evaluation of the shopping mall's fire systems integration at the landlord/tenant interface.

Integrating systems
The integration between the landlord and the tenant systems gives the greatest problem for the system integrator due to two main factors:

• the amount of connections required between the systems;
  
• the requirements of signals to latch and the capability of remote reset.

The tenant system is normally expected to initiate an alert or evacuation signal to the local area being covered, and then communicate this status to the landlord system. The tenant retail outlets either side of that with a fire condition are normally required to change from the normal status to an alert status.

This cross-linking to the adjoining tenants can become quite complex, and the speed of response can become critical in such situations. The solution for these systems is good planning at the start and a comprehensive understanding of the capability of both the tenant and landlord systems.

The actions taken at the landlord system depend on the type of system installed. Such actions could range from monitoring the alarm situation and co-ordinating the required emergency services; through to active control of the site with voice annunciation and evacuation procedures.

Figure one, over, shows an example of the interfacing that is needed between the tenant fire alarm panel and the landlord system.

The majority of tenants comprise small shops within the shopping centre, hence they need only a conventional fire alarm. The landlord system must cover a large physical area and individually monitor each tenant system, so an analogue addressable system is used. Figure one shows that five signals are ideally required between the two systems. In reality, only a few conventional systems offer a separate alert output and the number of interface lines becomes four (two-in, two-out).

Advantages can be gained from installing a small single- loop analogue control panel in each tenant site, although the size of the area being covered does not warrant the necessity of an analogue system. The main advantage is only realised when the landlord system is communicating with the same protocol as the single-loop control panel that is installed within the tenant's property. The problems of interfacing is eliminated as the panels can co-exist on the same network, and the fault reporting levels are greatly enhanced ie pre-alarm and exact smoke and heat reporting.

This situation can have attendant problems, as not many systems will have all the tenants' and landlord's communications configured with the same fire communications protocol. Also, there is a physical limit for the amount of control panels that will run on the network.

The limitations for the landlord's analogue fire alarm system are that each tenant with a conventional fire alarm system will require a minimum of two interfaces. For most fire alarm protocols this means a limit of 63 tenants per loop (63 x 2 = 126 addresses). In practice it is not sensible to fully load a loop, hence the realistic limit would be nearer to 50 tenants per loop. Thus, in a large shopping centre a significant number of loops could be consumed with monitoring the tenants' fire alarm systems.

Advances in technology
The technological changes that have taken place in communication protocols are gradually being translated into life safety. Products now exist that have a single loop address that allows eight inputs and eight outputs. This style of product can significantly reduce the number of interfaces needed and minimise the installation time and cost.

Hochiki Europe, for example, has designed a module that allows system developers to make a product specifically for their needs. A dedicated shop interface could give a significant advantage to the tenant/landlord scenario. With the capability of eight inputs and outputs, this would give a six minus one reduction on interfaces required on the system. It would also increase the monitoring capability from 50 to 300 tenants per loop (based upon three tenants sharing one interface). No functionality is lost as each of the inputs and outputs has an individual address.

Hochiki's Enhanced System Protocol (ESP) has been installed extensively on many sites ranging from large hospitals to the new Parliamentary building in London.

Cost savings
The advantage of local control is the speed with which adjacent tenants can be alerted, the localised decision processing, and the simplified programming.

Such innovations allow the tenants to have a simple conventional fire alarm system, and obviate the need for the tenant and landlord systems to be the same.

Often tenants and landlord systems are bound to a closed protocol for fire data communications, which can mean users are tied to expensive maintenance agreements with no options for competitive tendering. All the benefits of this advanced style of system are available from an open protocol supplier, with the advantages of allowing either the tenant or landlord to put the maintenance of the system out for competitive tender to yield the lowest cost of ownership possible, without sacrificing support or life safety.