Completely automated with KNX

Automated building management systems are gradually replacing classical electrical installations. The right KNX power supply ensures problem-free operation.

The installation costs for a smart electrical installation are falling continuously. Combining various building-services subsystems removes the need for individual sensors and controls, leading to installation cost advantages, and although the up-front costs for an automated system are higher, they are quickly amortized. By monitoring and controlling the technical building facilities with networked sensors and actuators, energy demands and maintenance costs are kept to a minimum. Moreover, the system takes over all necessary processes completely autonomously.

There is hardly a bus system on the market supported by as many producers as the KNX bus.

• The bus itself requires a power supply with rated voltage of 24V (in addition to 230V mains for powering the devices). With KNX TP (twisted pair), this operates together with the data signals on a two-wire cable.

• The necessary power supplies, depending on the manufacturer, provide from 28 to 31V, i.e. somewhat more than the rated voltage. They thus provide a buffer, e.g. for line losses or other losses, and the KNX bus couplers work perfectly down to a minimum of 21V.
• When the bus is idle (logical ''1''), the supply voltage from the power supply is present. The logical ''0'' is generated by an alternating voltage. To transmit a ''0,'' the sending KNX device lowers the voltage briefly by approx. 5V. This results in an immediate equalizing pulse through a serial choke built into the power supply unit. The information can only be utilised by the receiver because of this change in voltage.
• The CSMA/CA access procedure (Carrier Sense Multiple Access/Collision Avoidance) excludes data losses caused by collisions.
• KNX standardisation is listed in the DIN EN 50090, EN13321-1 and 2, and ISO/IEC 14543-3 standards.

In the past, because of the required electrical cabling, systems for controlling the technical equipment in residential and commercial buildings were rather complicated. This is why the KNX system was developed – a new, manufacturer-independent form of installation that allows communication between any arrangement of controls, sensors and actuators.

• The basic KNX TP installation requires no more than a routed, two-wire installation bus that transfers signals between devices as digitised values and control commands in telegram style.

• The system thus reduces the amount of electrical cabling in the building, has a reduced fire load and needs less maintenance.
• An automated building management system can be very simple and involve only a few connected devices.
• KNX was developed to allow highly integrated systems with many thousands of connected devices to be implemented as simply as possible, e. g. in a building complex.

For a KNX system, special power supplies are needed to deliver power to the bus system, and these units are not interchangeable with standard power supplies.