Wireless Hybrid Systems: FAQ

I’m hearing a lot about hybrid wireless fire detection at the moment. What is it and why does it matter?

Hybrid wireless fire detection has become increasingly popular over the last few years. It refers to the design, specification, and installation of a fire detection system that comprises hardwired, analog, addressable technology alongside wireless-based equipment.

Modern hybrid wireless systems deliver fully intelligent field device integration, allowing analog values, device addresses, and type codes to be transmitted to a system’s control panel. Wireless units can be installed and the devices added to an existing system simply by using an appropriate translator module.

In its early days this technology was derided for its unreliability, but these issues have been addressed, and it is now seen as the ideal solution for buildings where traditional fire detection is not deemed suitable.

I’ve been asked to install a fire detection system in a listed building, and in certain areas the fabric of the structure must not be disturbed. Would a hybrid wireless system be OK to use?

It is precisely this type of application where hybrid wireless systems are particularly beneficial, so the answer is a resounding yes.

For architects and others involved in the renovation of listed buildings, the challenges posed by fire detection system provision can be difficult to overcome due to the types of materials used in such properties, as well as the regulations concerning structural change and rewiring. In these circumstances, hybrid wireless fire detection is the only realistic option.

However, hybrid wireless systems are also suitable for other environments, and we are seeing them successfully used in temporary structures in hospitals and educational establishments, as well as buildings that are spread across a site, such as exterior classrooms. Also, in buildings where asbestos is present, it offers an ideal way to keep occupants safe without disturbing this potentially lethal material.

What disadvantages does it have?

Wireless technology isn’t suitable for every application. For instance, one disadvantage of a hybrid wireless system that should be considered is that signal strengths are affected by different structural media. For instance in a historical building with 5-meter-thick walls or in a modern mobile unit consisting of a metallic structure, obtaining the required signal strengths can prove difficult. However, even in these environments wireless protection can normally still be achieved, but a great deal more consideration should be given.

With regard to the technology itself, in some circumstances signal times with regard to cause-and-effect capabilities can be a problem. Also, there are the dynamic capabilities of sounder tones to consider. Wired systems can have more than 50 different tones that can be used to signify different things, whereas a wireless system will usually only operate on a single set tone.

I’m in the process of choosing a hybrid wireless fire detection system. Should I look for compliance with any particular standards?

Since March 2011 all wireless fire detection systems have to comply with EN 54-25, which is now the common standard across Europe and the main reference point for this technology.

It was established to ensure that wireless and hybrid wireless fire detection systems provide the same level of protection as their hardwired counterparts. EN 54-25 specifies the requirements for how these systems operate, such as bi-directional communication, redundancy through dual battery back-up, minimum battery life, improved fault monitoring, and defined product testing procedures.

Each device must be marked with the number of the standard, the name of the manufacturer, the model, a CE mark, and the notified product certification body number. Any systems that do not have all of these marks should be avoided, and it is also a good idea to seek evidence of third-party testing.

I’m not sure how to ascertain whether a customer’s building is suitable for hybrid wireless fire detection. What would you advise?

Being able to ensure that this technology will work within a building requires a radio site survey. It is perhaps the most important element of any wireless installation process and must be thorough and comprehensive, as much of the subsequent configuration will depend on the results.

It’s always preferable to do this physically by visiting the site, but in situations where a system has to be designed “off paper” as part of a tender, there are some good software packages around that can help configure the right specification.

A word of warning though — carrying out a site survey can be a time-consuming process and can typically take a full day or more to complete, depending on the building. This means lots of invested time at the tender stage or at the beginning of a job, so make sure that it’s a cost that you factor in.

What pitfalls should be avoided when conducting site surveys?

The main pitfall to avoid is carrying out a radio site survey when a building is empty or not being used in its normal manner.

Customers often ask surveyors to attend a site during quiet periods or other downtime. This is especially common in schools and other educational establishments, where such an activity might be more convenient during school holidays. However, this should be avoided, as it does not give a true representation of the obstacles faced by wireless signals on a day-to-day basis.

The structure of the building, including doors and windows, as well as people and the electronic devices that they use — mobile phones, computers, machinery, third-party radio equipment, etc. — can potentially have a significant impact on the ability of signals to operate at full strength and can drastically affect the tolerance of values. Therefore, it is always advisable to carry out the survey when it is fully occupied.

My advice is to look for the worst-case scenario and design accordingly, by building in sufficient levels of redundancy, in particular when you are considering the quantity of radio transmitters/receivers.

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