Secure construction site operations

Merz GmbH, Gaildorf


Quality and practicality of a construction power distributor can directly decide the success of a construction project. Merz GmbH, located in the Swabian town of Gaildorf, is specialized in distribution boards for construction sites. The company covers four competence areas: mobile distributors, testing equipment, switching devices and sheet metal technology. From the plugs, right down to the enclosure manufacturing, Merz can rely on in-house components and services. Merz only sources special devices from selected suppliers. For residual current protective devices, Merz has been relying exclusively on Siemens since 2008. Today's challenge: More and more cranes, cement mixers and other heavy machinery at construction sites use frequency converters. They control the motor speed electronically and thus play an essential role in saving energy and reducing material wear. However, converters require special protective devices. Many older or also less high quality distribution boards for construction sites are not designed for this.


Totally unlike the systems from Merz: The traditional Swabian company guarantees the highest safety standards in the operation of frequency converters. Specifically with the SIQUENCE 5SM3 RCCBs of type B/B+ from Siemens – for protection in the event of smooth or virtually smooth DC residual currents, which can be caused by frequency converters used in a construction site environment. These electronic speed controls are used, for example, in crane drives, but also in pumps, ventilators or modern cement mixers. The DC residual currents block the switch by pre-magnetizing the converter. In the event of a fault, this creates the risk of a life-threatening electrical shock. Siemens was the first manufacturer already back in 1994 to introduce the SIQUENCE residual current operated circuit breaker (RCCB) type B/B+, especially for smooth DC residual currents. Residual current protective devices are required for the operation of frequency converters, also in the definitive standards and directives: for instance, in EN 61439-4 (low-voltage switchgear and controlgear assembly Part 4: Special requirements of distribution boards for construction sites).

Customer benefits

Frequency converters are also increasingly becoming standard in construction machinery. This creates new requirements of distribution boards for construction sites. With RCCBs oft type B/B+ from the SENTRON portfolio, the Merz company's distribution boards for construction sites provide maximum safety: Production downtimes are prevented, and all personnel on the construction site are reliably protected from dangerous accidents caused by electricity.