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Radio or wireless systems have obvious advantages in installation compared with any form of hard wired system. Early systems generally utilised direct broadcast ‘Star’ communications where each device would communicated directly to the control panel, although sometimes this was possible through a repeater device to extend the overall range. More recently, ‘Mesh’ technology has allowed a wider range of possible topologies with some resilience being incorporated through dynamic multiple path management. Both approaches have positive and negative factors to consider and a radio site survey is always essential. Whilst the benefits of installing wireless systems without any cables is clear, the complexities of radio transmissions and the many factors that affect their integrity, must be given serious consideration to ensure long term trouble free operation.
The first point to make is double edged: any proposals for a radio fire alarm system must be verified by site survey and any quotation should be underwritten by the service provider to ensure any unforeseen eventualities are covered within the proposal.
The site survey for a wireless system must be carried out on the actual physical premises and never be estimated from drawings, plans or photographs as hidden services such as pipework, cabling, and steelwork can have a hugely detrimental effect on signal strength. In addition, the site should be in a similar condition and level of usage to that proposed as changing furnishings such as steel cupboards etc, and increasing the number of persons can affect system operation. Survey equipment should accurately replicate the characteristics of the devices being used and record both the signal strength readings and the background noise levels; a survey tool one based upon a standard device (and its aerial configuration) will give a true view of how devices will operate in that environment. Note that some manufacturers offer survey kits based upon a standard radio detector which generally gives a more reliable survey reading than a bespoke tool which may utilise different radio circuitry and aerials.
Underwritten quotations are essential, where the service provider takes full responsibility for the results of the radio survey and will install the system to a fully operational state without any additional costs. Unforeseen effects on radio transmission often occur and additional devices (ie, signal boosters, radio clusters, larger aerials etc) may be required and can generate additional costs. The more experienced manufacturers and suppliers may seem to be more expensive at first glance, but due to their expertise their guaranty of trouble free operation is absolutely essential if potentially large cost over-runs are to be avoided. Recent changes in regulations have forced manufacturers into a relatively low power of signal in the region of 868mHz along with many other types of wireless devices and this has led to many clashes and interference issues.
Star format communications allow each device to talk directly (or through a single path type repeater / booster) limit the size of system and lack the resilience of the more intelligent mesh type network. This style of system should only be utilised for smaller projects and a large safety margin in signal strength above the background noise level should be maintained.
Mesh technology allows automatic rerouting of communications as the radio environment changes in order to offer a high degree of resilience. Some or all devices may operate as signal repeaters for more remote device signals and the path may change accordingly to maintain the strongest signal strength. This is very complex technology and the way it is implemented by different manufacturers varies greatly and hence its effectiveness also. However, battery powered devices that operate as relay stations for communications between devices may suffer from reduced battery life. It is desirable that the more effective smart cluster technology is utilised where the mesh operation is limited to devices specifically designed for this purpose (ie, not a detector, call point or sounder) and that they should be powered from the mains supply with a battery backup.
Certain types of building are ideal candidates for wireless technology, ie, listed buildings, cathedrals etc, many other categories of project may also be benefit from the reduced disruption to daily business, ie hotels and showrooms.
Recent hybrid technology gives benefit where radio device controllers may be connected to the loop of a hard-wired addressable system for extension into areas unsuitable for cable installation. This gives simplicity of maintenance for the hard-wired part of the system and the convenience of wireless devices in limited remote areas. Before considering this approach, some careful scrutiny of all aspects of the products being considered should be made as the effective operational details vary greatly. Generally, reference within the industry should be sought, forums should be read etc.
Detection device technology varies according to manufacturer, and both the simple two-state conventional style and the multi-state intelligent analogue style of detection are available.
Radio systems are rarely suitable for large projects and will require very careful planning and an underwritten guaranty. Small projects are generally a lot simpler, and the use of hybrid wired & wireless technology further stretched the appeal of these systems. Take care to balance the savings in installation costs against the higher cost of equipment and high ongoing maintenance requirements.
The experience of the ‘Installation Contractor’ is extremely critical and oversight directly from the manufacturer is strongly recommended on all but the simplest projects. Unfortunately a large number of systems have been installed poorly over the years and many end up being replaced due to the installers inability to rectify ensuing problems.
In assessing the suitability of any type of system for your application, often the practical experience of an engineer experienced in exactly this technology (including the manufacturers own engineers) will give a lot more insight into daily practicalities than the manufacturers sales driven ‘Marketing’ information.
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