Overvoltages in loops - Basic Documentation - RMK770-1

Communication via the KNX bus

Product Family
Product Group
Air conditioning controller
Content Language
Content Type
Basic Documentation
Document No
Download ID
Stock No.
Product No.

Loops are frequently the cause of electromagnetic interference (EMI) and surges resulting from lightning strikes. Loops occur when two independent networks (e.g. the KNX network and the AC 230 V mains network) are connected to one bus device.

Avoid loops

Lightning can generate powerful surge voltages in loops, which cause short circuits in devices and damage electronic components irreparably.

It is important at the outset of engineering to avoid loops where possible, or to keep the extent of any loops (the "loop area") as small as possible. The formation of loops must be considered in relation to the entire installation and all conductive components must be taken into account, because the significant aspect of a loop is its overall area.

Note also:

  • Bus and mains voltage conductors (power cables) must be routed as close together as possible. This also applies to earthed components, if they are in contact with the bus devices during normal operation.

  • The distance between conductor ends, earthed components and other conductor ends should be as great as possible.

  • Maintain an adequate distance from the lighting protection system (e.g. from arresters).