By Iain Gordon, KNX UK President and Managing Director of GES Digital Ltd

When is a standard not a standard? For me the answer is clear. It’s when you are effectively at the mercy of a manufacturer to keep supplying and supporting the devices you specify as part of what is probably a five-figure project.  If they don’t (and we’ve probably all had experience of this) then, no matter how smart it was at the outset, the installation just won’t work without a lot of time and expense even if it’s only something as simple and seemingly insignificant as the PIR switches fail and are discontinued.

Naturally I’d say that the open protocol approach is best,  that can only mean KNX, which gives you a choice of thousands of devices from hundreds of manufacturers with guaranteed compatibility.  It covers all the bases: heating, lighting, security, automatic doors/windows andAV. They can all be programmed to act in concert and in automatic response to KNX-compatible movement, temperature and air quality sensors, or under the command of wall-mounted control panels or phone/tablet interfaces.

Programming is achieved using the KNX software which is continuously and well-maintained not least because, after more than a quarter of a century, manufacturers and integrators around the world have far too much invested in KNX to allow it to be otherwise.
As technology evolves, there is naturally a move towards RF and wireless in the controls world and it most-certainly has its place. I’ve even heard KNX described as ‘dated’ because it relies on bus cabling and relatively low bit-ratesI see it as robust and reliable – and I’m not alone in having built a successful business on the basis of that reliability.

Nevertheless, KNX isn’t ubiquitous and probably never will be. There is always a place for other approaches in a healthy market, but I have no doubt that KNX control will continue to grow in popularity and will emerge as the master control system of choice.

For instance, other standards tend not to offer holistic building control and are better suited for, say, industrial HVAC and interfacing BMS/BEMS (building management systems/building energy management systems). That’s why manufacturers offer gateways between the core standards to connect two networks. In domestic premises, I would always recommend using KNX throughout. In any building under construction or undergoing renovation work, it’s worth thinking about putting in KNX bus cable alongside traditional wiring so you can ‘draw down’ on it later. KNX distributes intelligence to device level, and it is possible to implement it one room or one department at a time. Suffice it to say there is potential to have as many as 64,000 devices on a single system or just a handful controlling one room – with no restriction on daisy-chaining and growing from one end of the scale to the other as you wish.

 

So, what are the other names you may have heard of, and how do the fit into an open KNX world?

Building Automation Controls Network (BACnet): BACnet is a network protocol specifically used for multiple devices to communicate across building automation systems. It is popularly used for commercial HVAC control and most building energy management systems (BEMS) use or support it. BEMS systems, in turn, offer good visualisation of energy usage. I would argue, however, that they tend to show you what is happening, rather than getting on and rectifying the problem as a smart KNX installation would do – adjusting heating, lighting and security responses in real time.

BACnet has relatively little to offer in lighting control and KNX is increasingly chosen to work alongside it where traditional BEMS systems are still appropriate. Manufacturers like ABB produce KNX/BACnet gateways to link the HVAC control network with all other aspects of building management, including DALI lighting.

Modbus: Modbus is a network communications protocol best used for industrial automation systems specifically for connecting electronic equipment over serial lines in a master (requesting information) /slave (transmitting information) configuration. Although Modbus is best for industrial applications, its simplicity leads some system designers to use it with BMS/BEMS.  

Lon Works: LonWorks is a communication network protocol useful for building automation applications designed on a low bandwidth, for networking devices through power lines, fibre optics, and other media. It is less commonly found these days, has had limited impact beyond the industrial and commercial markets, but it is being leap-frogged by the open KNX approach.

EnOcean: EnOcean focusses on wireless communication. The well-established EnOcean wireless standard is optimised for use in buildings, with an indoor radio range of up to 30m. Interoperable products are offered by various manufacturers, self-powered by motion, light or heat, and can communicate directly with each other and/or they can be controlled by a room controller/gateway. No cabling is needed, which is popular in sensitive and listed buildings.

The ease of integrating EnOcean sensors within a KNX solution means that Enocean can also be useful in very large-scale installations where appropriate.

DALI: The Digital Addressable Lighting Interface (DALI) probably needs little introduction to BSEE readers. The underlying technology was established by a consortium of lighting equipment manufacturers, as an open standard alternative to Digital Signal Interface (DSI), on which it is based.
A DALI network consists of a controller, a power supply (which may be built into the controller) and one or more slave devices (eg ballasts, drivers and dimmers) that have DALI interfaces. The controller can address devices individually or by multicast. There’s nothing here that KNX cannot do as well, but there is an army of talented and loyal DALI lighting designers out there. For them, the KNX world offers gateways to integrate DALI lighting with other aspects of building control.

Systems like Lutron, Crestron and Control 4 all enjoy well-earned market share and there are some amazing products and installations out there that have really raised the game on interior look and feel. However, they all have one thing in common: they are not standards.  The underlying weakness is that they are proprietary solutions ie they are completely reliant on one manufacturer. While offering holistic control, their HVAC control is still relatively limited and reliant on interfaces between systems. Their central processor architecture means a single event can disrupt the entire system. This can if course, be offset using  KNX drivers and integration gateways which are readily available. In fact, it’s not unusual to see, a KNX installation with, say, a Control 4 designed home cinema or AV system as part of it.

In conclusion, any installation is a mix of the technology and the talent of the system integrator. People buy from people they trust, and there are great system designers using all of these systems. All the same, I’d recommend hedging your bets and making sure any building is open to whatever the future brings and make sure it is KNX ready.