Customer application September 18, 2020

Uncompromising Safety – Electrical Installation at the University Hospital

In the central area of Building 23, WAGO’s TOPJOB® S Through and Multilevel Installation Terminal Blocks ensure that electrical wiring is safe and reliable.

Safety is paramount during electrical wiring. And this is critical to buildings that house scores of patients and staff. To ensure safety in common scenarios like this, the VDE 0100 safety standard contains requirements, such as that the neutral conductor must not be disconnected during testing of insulation resistance. These measurements can be easily performed using multilevel installation terminal blocks with an internal N-disconnect from WAGO’s TOPJOB® S portfolio.

The University Hospital was founded 100 years ago as part of Goethe University in Frankfurt am Main, Germany. Today, more than 4,000 employees work in 32 specialized clinics and institutes. The facility houses nearly 1,200 beds for the more than 50,000 patients who receive in-patient care annually. The University Hospital, which spans 50 buildings in a 433,000 m2 area, is large enough to almost be its own Frankfurt neighborhood. Thus, renovations and new construction are the rule rather than the exception for the bustling facility. Within the last four years, construction projects have snowballed, including extensions to the surgical departments and renovations of existing buildings. Work on the basement, which will house outpatients from internal medicine, is currently entering its final phase. The dedication is planned for the end of 2014. In the in-patient areas, two-bed room standard continues to be implemented consistently. Patients can expect modern spaces and bathrooms in the near future.

Frankfurt University Hospital

  • Electrical Power Supply
  • Fuse Protection is Critical
  • Testing per VDE 0100 – Fast and Safe

Electrical Power Supply

Imtech GmbH & Co. KG was awarded the contract to work on the electrical installations in the central area of Building 23. This power and building technology company has more than 5,000 employees and constructs its own control cabinets at its facility in Illingen, Germany. The Imtech facilities in Frankfurt and Illingen collaborated closely on the University Hospital project. In all, 200 distribution boards were built, installed on site and connected to the hospital’s systems. Design and construction of the distribution boards occurred at Imtech’s Illingen manufacturing facility. The connection-ready distribution boards were delivered, installed and connected by the workers from Imtech’s Frankfurt office. In addition to the distribution boards that were installed in specialized utility rooms, nearly 80 ceiling-mounted distribution boxes were required for integration into the building’s suspended ceilings. These were also manufactured in Illingen, then installed and cabled on site.

Every device in the building is supplied with electrical power from these wiring distribution boards. In addition to general facilities, like administrative offices and doctors’ and nurses’ offices, these also include patient rooms, as well as operating rooms and treatment rooms. The latter areas include X-ray machines, lasers and other medical devices that need electricity. The ceiling-mounted distribution boards are equipped with WAGO’s 2002-3217 TOPJOB® S Through Terminal Blocks, which enable a change in conductor size from 4 mm2 (12 AWG) to 2.5 mm2 (14 AWG). With a conductor size of 2.5 mm2 (14 AWG), the maximum permissible conductor length is only 25 m. Since the distances between the distribution boards and loads are often longer, the conductor size must be adjusted in the ceiling-mounted distribution boards. This highlights an important benefit: ease of wiring. Since the electricians must perform overhead cabling work while standing on scaffolding, rail-mount terminal blocks equipped with push-in connection technology are extremely advantageous.

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Fuse Protection is Critical

Imtech also relies on this connection technology, found in WAGO’s TOPJOB® S Multilevel Installation Terminal Blocks, for the distribution boards. “The spring pressure connection technology in the installation terminal blocks saves a lot of time during assembly and guarantees durable, maintenance-free connections,” says Sebastian Löw, identifying the key advantage of the terminal blocks. As the project manager for switchgear construction in the Illingen branch, he was responsible for the project. All of the distribution boards’ outlets are equipped with RCD circuit breakers. And these are divided into two types. First there are conventional circuits that supply normal lighting or sockets. “In this case, there were an increasing number of outgoing circuits that were protected with RCD circuit breakers,” explains Matthias Renzig, the electrical site engineer who is managing the on-site wiring of the distribution boards. The outgoing circuits were created using WAGO’s 2003-7641 Multilevel Installation Terminal Blocks. An N-busbar links the N-disconnect slide links, which are protected using a common RCD circuit breaker.

Secondly, there are outgoing circuits to sensitive areas that had to be individually protected with an RCD circuit breaker for each circuit. A typical example of this would be the “bed head” wall power supply strips in the patient rooms. These bed strips supply the hospital beds with electricity, oxygen and compressed air. The call system and the data connections are also integrated into the bed strips. Patients’ medical devices can also be plugged into sockets that are integrated into the bed strips. The individual breakers on these circuits are intended to prevent a medical equipment failure if a defective device is connected to a neighboring socket. Under certain circumstances, triggering the RCD circuit breaker could have life-threatening consequences for the patient. Therefore, Imtech chose WAGO’s 2003-6641 Multilevel Installation Terminal Blocks with an internal N-disconnect to wire the distribution boards for these outgoing circuits. Even the conductors for these circuits have to satisfy specific requirements: They must be (N)YM-(St)J sheathed cables that can effectively shield their electromagnetic interference fields.

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Testing per VDE 0100 – Fast and Safe

Measuring insulation resistance within the outgoing circuits, both after installation and for regular retesting, is recommended in order to guarantee the safety of the hospital’s electrical wiring. VDE 0100-600 and VDE 0100-718 specify how these measurements are made. For example, the neutral conductor must not be disconnected during the measurement. The conductors for the N and L phases may be connected to each other during testing, expediting the process. And this is where the inherent advantages of WAGO’s multilevel installation terminal blocks are the most apparent. The terminal block variants with an internal N-disconnect carry a pivoting disconnect knife that can be easily opened using an operating tool. After the phase of the corresponding circuit has been switched off with the line circuit breaker, the neutral conductor is disconnected with the disconnect knife. At this point, a specialized test plug adapter that links the N and L conductors can be inserted into the shaft, which is now free. This permits insulation resistance testing for both using just one measurement.

60 Imtech electricians were involved in the installation of the 200 distribution boards and 80 ceiling distribution boards in the University Hospital. “Our wiring work was much easier because the connections to the various terminal blocks from WAGO were implemented using spring pressure connection technology.” says Löw, convinced to the benefits: “This was one of the essential reasons why we decided several years ago to select WAGO as our leading supplier.” The maintenance-free connections were deemed another significant advantage of the spring pressure connection technology. Imtech has also been very satisfied with both the comprehensive product portfolio and its great partnership with WAGO Support. Renzig is convinced: “Just using the multilevel installation terminal blocks with an internal N-disconnect saved us a great deal of time during the commissioning tests according to VDE 0100.” And this advantage will continue to pay dividends for the operators during the regularly scheduled repeat testing.

Summary:

  • Through and multilevel installation terminal blocks ensure the safety and reliability of the electrical wiring.
  • Spring pressure connection technology saves time and ensures reliable, maintenance-free connections.
  • Multilevel installation terminal blocks with internal N-disconnect save time during the commissioning test.

By Torsten Weichel and Erich Höfler | 2014-11-01

Photo: Klaus Ohlenschläger/vor-ort-foto.de

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