Making the most of wireless technology

The world of electrical installation is changing, more radically and rapidly than would have been thought only a decade ago. Driven by the trends of intelligent buildings and, naturally, of cost and time reduction, it’s becoming a technological activity rather than a physical one. Emerging technologies are freeing installers from the constraints of complex wiring and power sources; providing greater intelligence and adding more value.

Whether for new builds, refurbishment or buildings maintenance, all of the construction trades, disciplines and associated technologies face the same multiple challenges. They all need to drive costs down and reduce installation times and they all face a growing mountain of regulation, especially health and safety and environmental legislation.

Labour costs are an obvious place to start. Modular solutions and off-site construction have been adopted in many sectors from pre-cast concrete modules, ready-to-install windows and doors, to pre-built control panels and cabinets. These reduce the amount of time required on site, de-skilling the on-site tasks.

Electrical installers are increasingly deriving the benefits of similar approaches. Through the use of modular, and rail-mounted standard components, control panels, consumer units and even wiring can be assembled off-site to reduced installation, test and commissioning time. But, as long as switches and sensors need power and a physical link to the actuators, lights, heating, fans and other loads, installation will be hampered by the inflexibility of cabling.

Cabling is the bottleneck

By its very nature, wiring is a first-fix activity and usually has to be done in situ, within a specific time slot. There is rarely a second chance once all the switches, sensors and loads are in place, and cabling has been run in conduit, particularly when chased-in. This demands physical skills as well as the knowledge required to work with (and in some cases, around), wiring regulations, risk assessments and other regulatory challenges.

There is only one way around this: get rid of the cable necessitated for switching. To achieve this, several wireless technologies are now established, enjoying varied levels of take-up. Zigbee, 802.11 Wireless LAN and Bluetooth are the most common. However a number of technical reasons hamper their success in electrical installations: in particular the limited range, data bandwidth and excessive power consumption dictated by the RF frequency, modulation and protocol of the technology in question.

Fortunately, there is one solution that overcomes these difficulties. The wireless, energy-harvesting technology pioneered by EnOcean is based on transmitting data in very short bursts, in the 868MHz band. The entire process is started, executed and completed in less than a millisecond. This means that, even when there are many transmitters in a confined space, data packets are highly unlikely to collide. It is also highly robust in the presence of other wireless signals from DECT and GSM phones, WLANs and private mobile radio. As many as 500 closely located transmitters, all signalling once a minute, can be received with more than 99.9% certainty.

Energy harvesting

Over and above its reliability and resilience, the major distinguishing feature of EnOcean’s technology is that very little power is required. A wireless switch would use just 50µW for a complete radio command – around one hundredth the consumption of alternative wireless switches.  At these micropower levels energy can be harvested from external sources, rather than relying on batteries or a wired feed. Switches are powered by the mechanical action of the finger on the button; thermostats by small solar cells; they can even harvest the energy of rotation, vibration or minor temperature differences.  At long last, switches and sensors are freed from the tyranny of wires and batteries. For installers, this brings a variety of specific benefits.

First, it eliminates the need for many physical first-fix activities and removes coordination issues. For example, switches can be attached without regard to other trades’ schedules, and connected without isolating the power. Sensors like motion detectors and light meters can be fitted in the best location for their application, unlike conventional devices that also need to be accessible for replacing batteries. What is more, this inherent flexibility means less night-time and weekend working, and reduces the need for site management, producing substantial savings in labour and transport costs. Better still, last minute changes, design constraints and broader individual preferences are much easier to accommodate.

Wireless installation can more readily satisfy the regulations. Such technologies are intrinsically safer for installer and user, especially in locations like kitchens and bathrooms. Also, with no cabling installed on walls, the necessity to protect lighting circuits with RCDs is potentially removed.

Cabling topologies are also greatly simplified, freeing installers to adopt a ‘radial’ point-to-point format. This spells the end for troublesome practices in ceiling roses, two-way or intermediate switching or junction boxes. Moreover, it paves the way for consumer units to become the intelligent hub using versatile multi-channel receivers rather than hard wired field terminations.

A major result is a sizeable cost reduction of about 10% on the entire building automation system when it is first installed. For example, installing 4,200 wireless sensors in one building alone saved over 30km of cable installation.  

EnOcean in action

Economies are even greater if the system is later re-dedicated – typically saving 80% of traditional costs. The 2007 refurbishment of the Mond Building on Cambridge University’s New Museum site is a case in point. Here, energy-harvesting wireless switches proved an ideal solution as they remove the need for chasing or for any wiring in walls.

Contractors P A Collacott & Co of Cambridge worked alongside consulting engineers K J Tait to refurbish this 1930s rotunda-style building using Echo switches from MK Electric (the first major UK manufacturer to incorporate EnOcean technology into switches).

Receivers were installed in the luminaire and wired into the lighting circuit at the time of ceiling installation. Self-powered switches were then mounted using either adhesive pads or screws depending on the location. Pads provide super-fast fixing or a dependable base for awkward surfaces like marble or glass; whilst screws were used where additional security was needed. The switch is simply aligned to its receiver by setting it into learn mode and pressing the rocker.

One receiver can be programmed so it can be operated by up to 30 switches; while, conversely, any number of receivers can be activated by a single switch. There is no need for the complexities, or the idiosyncrasies of switch wiring such as using the blue conductor as a switched feed. Where signals are obstructed by impervious materials such as granite or steel, repeater units divert or extend transmissions around the building.

A wireless future

MK is one of the 100-plus manufacturers world-wide that are working to further develop and promote self-powered technology for sustainable buildings by formalising the interoperable wireless standard. As members of a consortium of companies called the EnOcean Alliance, they are participating in a group that boasts the largest installed base of field-proven wireless building automation networks in the world, installed in more than 100,000 buildings. Market research firm WTRS has forecast that shipments of EnOcean modules will grow to reach $1.4 billion in 2013. 

Whatever wireless technology is adopted, the impact on electrical installation practices
will be substantial as it becomes less physical, more technological. Installers will have a whole load of new value to add.