Nov 1, 2014 - Building
Safety First – Electrical Installation In The University Hospital
Safety is an essential consideration during electrical wiring. And this is critical to buildings that house scores of tenants overnight. To ensure safety in common scenarios likes this, the VDE 0100 safety standard contains mandates, such as requiring that the neutral conductor may not be disconnected while undergoing insulation resistance testing. These measurements can be optimally performed using multilevel installation terminal blocks with internal N-disconnect from WAGO's TOPJOB®S portfolio.
The University Hospital was founded exactly 100 years ago as part of the Goethe-Universität in Frankfurt am Main, Germany. Today, more than 4,000 employees work in 32 specialized clinics and institutes. And the facility houses nearly 1,200 beds for the more than 50,000 who receive in-patient care annually.
The University Hospital, which spans 50 buildings over 433,000 m2, 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 for the surgical departments and renovations for the existing buildings. Work on the basement level that will house outpatients from internal medicine, is currently entering its final phase. The dedication is planned for the end of 2014. For the in-patient areas, the two-bed standard rooms are being systematically renovated. Patients can expect modern spaces and bathrooms in the near future.
Electrical Power Supplies
Imtech GmbH & Co. KG received the contract to work on the electrical installations in the central area of Building 23. The power and building automation specialists employ more than 5,000 associates and construct their own control cabinets at their facility in Illingen, Germany. The Imtech facilities in Frankfurt and Illingen collaborated closely on the University Hospital project. In all, 200 wiring distribution boards had to be built, installed on site in the hospital, and connected to the building systems. Design and construction of the wiring distribution boards was performed at Imtech's Illingen manufacturing facility. The connection-ready wiring distribution boards were delivered, installed and connected by the workers from Imtech's Frankfurt office. In addition to the wiring 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 offices, doctors' and nurses' quarters, these also include patient rooms, as well as operating theaters and treatment rooms. The latter areas include, X-ray machines, lasers and other devices that require electrical power. The ceiling-mounted distribution boards are equipped WAGO’s 2002- 3217 TOPJOB®S Through Terminal Blocks, which enable a change in conductor size from 4 mm2 to 2.5 mm2. With a wire size of 2.5 mm2, the maximum conductor length is only 25 m. Since the distances between the wiring distribution boards and the consumers are often longer, the conductor size must be adjusted in the ceiling-mounted distribution boards. This brings to light an important WAGO benefit: ease of wiring. Since the electricians have to perform overhead cabling work while standing on scaffolding, these terminal blocks with direct push-in technology are extremely advantageous.
Fuse Protection is Vital
Imtech also relied on this connection technology, found in WAGO’s TOPJOB®S Multilevel Installation Terminal Blocks, for the distribution boards. “The spring clamping technology in the installation terminal blocks saved a lot of time during assembly and guaranteed a durable, maintenance-free connection,” shares Sebastian Löw on the terminal blocks’ advantages. The project manager was responsible for distribution board construction. All of the distribution boards' outlets are equipped with residual-current circuit breakers. And these are separated into two types. On the one hand, there are conventional electric circuits that supply normal lighting and sockets. “In this case, there were an increasing number of outgoing circuits that were protected with residual-current circuit breakers,” explains Matthias Renzig, the electrical site engineer who is managing the on-site wiring of the distribution boards. The outgoing circuits are realized using 2003-7641 Multilevel Installation Terminal Blocks. An N-busbar links the N-disconnect slide links, which are protected using a common residual-current circuit breaker.
On the other hand, there are outgoing circuits to sensitive areas that had to be individually protected with a residual-current circuit breaker for each circuit. A typical example of this would be the “bed head” wall power supply strips in the patient rooms. These head wall units supply the hospital beds with electricity, oxygen and compressed air. The call system and the data connections are also integrated into the head wall units. Patients' medical devices can also be plugged into sockets that are integrated into the head walls. The individual breakers on these circuits are intended to prevent medical equipment failure if a defective device is connected to a neighboring socket. Under certain circumstances, triggering the residual-current circuit breaker could have severe consequences for the patient. Therefore, Imtech chose WAGO's 2003-6641 Multilevel Installation Terminal Blocks with 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 limit their electromagnetic fields.
Testing According to VDE 0100 – Fast and Safe
Measuring insulation resistance within the outgoing circuits, both after installation and for regular retesting, is prescribed in order to guarantee the safety of the hospital's electrical wiring. VDE 0100-600 and VDE 0100-718 determine how these measurements are made. As such, the neutral conductor may not be disconnected during the measurement. The conductors for the N and L phases may be connected to each other during testing, which expedites 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 internal N-disconnect carry a pivoting disconnect knife that can be easily opened using an activation tool. After the phase of the corresponding circuit has been switched off by the line circuit breaker, the neutral conductor is disconnected by the disconnect knife. At this point, a specialized test adapter that links the N and L conductors can be inserted into the shaft that is now free. This permits insulation resistance testing for both using just one measurement.
Sixty Imtech employees were involved in the installation of the 200 wiring distribution boards and 80 ceiling distribution boards in the University Hospital. “Our work during the wiring was tremendously simplified because the connections to the various terminal blocks from WAGO were implemented using spring clamping technology.” Löw continues, “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 clamping technology. Imtech has also been very satisfied with both the comprehensive product portfolio and a great partnership with WAGO Support. Renzig is convinced, “Just using the multilevel installation terminal blocks with internal N-disconnect bought 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.
- Through and multilevel installation terminal blocks ensure the safety and reliability of the electrical wiring.
- Spring clamping technology saves time and ensures reliable, maintenance-free connections.
- Multilevel installation terminal blocks with internal N-disconnect save time during the commissioning test.
Text: Torsten Weichel and Erich Höfler, WAGO
Photo: Klaus Ohlenschläger/vor-ort-foto.de