Clarkson Controls’ MD Malcolm Anson (pictured), describes what a truly wireless sensor system can achieve, and why specifiers need to be careful in their selection of options.
T
he rise of building management systems has spawned the need for a fast, reliable way for buildings to feed information back to those systems. Wireless sensor technologies are widely available for this purpose, and are especially good options for retrofit projects. The reduction in installation and maintenance costs makes them a hugely appealing option, and a report by US firm Navigant Research in 2013 predicted annual worldwide shipments of wireless nodes for building controls will surpass 36 million by 2020.
It is vital, therefore, to choose the right wireless solution. The key is to understand that wireless does not necessarily mean cable-less. This, while adding a layer of complexity to the debate – not least when it comes to terminology – should inform consulting engineers and installers as to which is the best option for their job. The two main choices in the wireless sensor market are a truly wireless solution whose sensors are powered by the energy in their environment, such as photovoltaic; and a second type, which although wireless in the way it communicates, requires a constant power supply via cabling. “We coined the term ‘cable-less, wireless’,” says Malcolm Anson, Managing Director of Clarkson Controls, who supply and fit EnOcean technology sensors manufactured by Thermokon. “It clarifies the difference between the two main types on the market.
“The cable-less, wireless sensors sleep most of the time,” he explains. “When the temperature or whatever value they are
sensing changes, it wakes the device, which then transmits the new value to a receiver.”
Power requirements
Because this type of sensor is in a ‘sleep’ mode for much of the time, its power requirements are quite low, so wiring for power is not necessary as it can be powered by an onboard photovoltaic cell with inbuilt power storage.
The other type of wireless, but cabled sensors operate more like a cell net phone system, so the sensors will be communicating constantly with neighbouring sensors and onto a receiver. “Because this type of sensor is constantly sending and receiving information, it needs to be constantly
The two main choices in the wireless sensor market are a truly wireless solution whose sensors are powered by the energy in their environment, such as photovoltaic; and a second type, which although wireless in the way it communicates, requires a constant power supply via cabling.
powered, and that is the difference. It needs a cable to it,” explains Anson. There are numerous pros and cons for each type of system. But ultimately, sensors which require constant power will require cabling, which effectively means that they lose the advantages of the ‘wireless’ approach, such as lower installation costs, after all installing 2 cores is no different to running 3 cores. Other considerations for the cable-less, wireless, route are where the architect wants to avoid unsightly cabling and containment.
Overall, the truly wireless route offers a lower cost and more visually appealing approach. However, specifiers and installers do need to be aware of the challenge of wireless which applies to both systems. A space fitted with wireless sensor technology before occupation may then be sectioned up with partition walls and office furniture which will affect the wireless signal.
Signal boosters
“When tenants move in, the first thing they do is partition areas,” explains Anson. “Then they will fit aluminium blinds between glass glazing which block the signals, as do large filing cabinets, so those are the things you don’t know are happening until the client moves in, the system will stop working, and on investigation see a partition that wasn’t there when commissioning was carried out.”
You really need to be cable-less, wireless to take full advantage of the cost savings. With the EnOcean technology there are numerous manufacturers out there doing complementary products, which to an installer is good news as they are truly compatible and you are able to mix and match between manufacturers.
26 BUILDING SERVICES & ENVIRONMENTAL ENGINEER AUGUST 2015
However, such issues can be dealt with speedily by the application of signal boosters to the system.
There are, of course, certain instances in which the wireless sensor option will not be adequate. Try operating a wireless only system in an old bank or building with metre thick walls and see how much information your BMS receives.
Repeaters “Particularly in listed buildings, you’ve got to be careful with the fabric of the building,” says Anson. “Old buildings have thick walls, which can cause problems for getting a signal through, so you might need lots of repeaters for example, to collect the signal and transmit it on, giving it extra legs.”
Even then, says Anson, it would seem counter-intuitive to specify a wireless system that still requires running cables and causing disruption during the install. As Anson says: “You really need to be cable-less, wireless to take full advantage of the cost savings. With the EnOcean technology there are numerous manufacturers out there doing complementary products, which to an installer is good news as they are truly compatible and you are able to mix and match between manufacturers.”
http://www.clarksoncontrols.co.uk/
Clarkson Controls specialises in the design, manufacture and installation of intelligent temperature control products and building management systems. Malcolm Anson is Vice President of the Building Controls Industry Association (BCIA).
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