Practical tips 23 February 2021
Practical Tips for Our Rail-Mount Terminal Block Systems

We’ve compiled helpful information for the correct handling of WAGO rail-mount terminal blocks. Here you’ll find answers to frequently asked questions on topics such as connecting/wiring terminals blocks, marking, commoning and official requirements.

Practical Tips for TOPJOB®S Multilevel Installation Terminal Blocks

How does wiring with multilevel installation terminal blocks work in control cabinets? What needs to be taken into account for installation and commissioning?

More Room in Control Cabinets with Multilevel Installation Terminal Blocks

Modern building installations are becoming more and more complex, and to save time and costs, distribution cabinets are being more and more densely packed with installation devices and terminal blocks. To keep things organized, WAGO’s practical marking strips are recommended when TOPJOB® S Multilevel Installation Terminal Blocks are used.
The CAGE CLAMP® connection with WAGO’s push-in connection technology makes wiring easy:
  • Solid and fine-stranded conductors with ferrules can be connected by simply pushing them in – quickly and without tools.
  • All other conductor types can be connected easily and safely by first opening the clamp.
  • After insertion, the operating tool keeps the conductor entry open and marks the clamping point, leaving both hands-free for wiring.

Tip: Save Time during Mounting and Operation

Building installation places high demands on rail-mount terminal block systems. In addition to installation and commissioning, it must also be possible to perform regular testing quickly, safely and easily. When WAGO’s multilevel installation terminal blocks are used, insulation resistance can be measured without disconnecting the conductors, as required by standards.

Fast, Safe Installation Thanks to TOPJOB® S Multilevel Installation Terminal Blocks

WAGO’s TOPJOB® S Multilevel Installation Terminal Blocks guarantee fast, safe building installation because they are designed for space-saving wiring applications in standard distribution cabinets. Extremely compact dimensions, like the short installation length, provide maximum space for conductor termination. Featuring a large cross-section range from 0.25 to 6 mm2 (22–4 AWG), these terminal blocks cover all application areas of modern building installations.

In combination with 1 mm (0.039 inch) thick end and intermediate plates, carrier terminal blocks can also be used with fuse plugs.

Thanks to spring pressure connection technology, these terminal blocks facilitate push-in termination of solid conductors and fine-stranded conductors with ferrules. Because only solid conductors are permitted to be used for wiring electrical circuits in building installations, the multilevel installation terminal blocks offer enormous time benefits for connection. The easily accessible, perfectly angled conductor entry ensures that conductors can be securely inserted at a convenient angle. Retightening screws during system operation is a thing of the past. Potential errors such as over-tightening screws are also eliminated. The TOPJOB® S Rail-Mount Terminal Block System also provides clear organization of the electrical circuit wiring in the distribution cabinet, thanks to the clear association of conductors to each clamping unit, as well as the easily visible terminal block marking for all levels. Marking strips affixed on the upper terminal block level allow marking with up to three lines and are not concealed by the connected conductors – even when wired. With the comprehensive, practical TOPJOB® S Jumper System, you can handle every conceivable commoning task. For example, the adjacent jumper for continuous commoning provides unlimited potential multiplication in a single jumper slot.

Correct, Fast, Standards-Compliant Insulation Resistance Measurement

After installation, the regular tests are performed. Standards DIN VDE 0100-718 and DIN VDE 0100-482 specify that it must be possible to measure the insulation resistance to ground for each outgoing circuit for conductors smaller than 10 mm2 (8 AWG) without disconnecting the neutral conductor. Measurements can only be taken correctly in accordance with the standards when one wire per clamping unit is connected. Because this is exactly what the product standards for rail-mount terminal blocks with spring clamp technology provide, you are always on the safe side with WAGO’s TOPJOB® S Multilevel Installation Terminal Blocks. As soon as two conductors are connected in just one clamping unit, which is permitted for use with screw-clamp terminal blocks and other cases, no standards-compliant insulation resistance measurements can be taken. This is because one wire must be disconnected, which is not permitted.

Multilevel Installation Terminal Blocks Become Fuse Terminal Blocks

Multilevel installation terminal blocks with internal disconnection complete the TOPJOB® S program for building installation and allow economical wiring of smaller circuit groups. The carrier terminal blocks of these new variants can also be used as fuse disconnect terminal blocks. The TOPJOB® S Fuse Plug for microfuses (5 x 20 mm) can be used in the carrier terminal block slot. The new 1 mm (0.039 in) thick end and intermediate plate adapts the terminal block width to the fuse plug width. The DIN-rail-centered slot is ideal for applications in small distribution cabinets. Fuses can be easily checked and replaced via the standard cover cut-out.

Multilevel Installation Terminal Blocks – the Economical, Future-Proof Choice

Multilevel installation terminal blocks guarantee that insulation resistance measurement complies with standards, which will grow in importance for the future, for example due to E-CHECK. Terminal blocks with push-in connection technology guarantee economical, permanently reliable installation. The clearly visible structure and legible marking provide explicit identification of the electrical circuits. This provides the best foundation for permanently reliable operation of electrical equipment.

Tip: Multilevel Installation Terminal Blocks with N-Disconnect – Sure, But Which Ones?

From a technological standpoint, buildings must be completely safe. In addition to thorough structure analysis and proper implementation, the electrical installation plays a particularly critical role. One safety measure is the insulation resistance measurement performed at commissioning and during regularly repeated tests.
This test is mandatory in fire-prone locations according to building code DIN VDE 0100-482 and for public buildings according to DIN VDE 0100-718. This standard specifies that it must be possible to measure the insulation resistance of all conductors to ground for each outgoing circuit for conductor cross-sections less than 10 mm2 (8 AWG) without disconnecting the neutral conductor. The N-disconnect is required.
Installation terminal blocks with N-disconnect are a recognized solution for meeting these demands.

Alternative 1:
Multilevel installation terminal blocks with N-disconnect slide links for mounting with N-busbar

Alternative 2:
Multilevel installation terminal blocks with internal N-disconnection for mounting without N-busbar

The state-of-the-art TOPJOB® S Rail-Mount Terminal Block System from WAGO offers two alternatives for building installation:

  • With N-disconnect slide link: 2003-76xx for cross-sections from 0.25 mm2 to 4 mm2 (24–12 AWG), 32 A

  • With N-disconnect slide link: 2005-76xx for cross-sections from 0.5 mm2 to 6 mm2 (20–10 AWG), 32 A

  • With internal disconnect: 2003-66xx for cross-sections from 0.25 mm2 to 4 mm2 (24–12 AWG), 25 or 28 A

Which connector should be used, and when?

The number of individual electrical circuits that can be protected by one RCD switch must be established separately for each installation. Likewise, the installer can select from the two possible installation setups. Which of these terminal blocks should be used for installation is determined by this number.
The multilevel installation terminal blocks with N-disconnect slide link are ideal for the electrical installation of larger electrical circuit groups with only a few RCD potentials. The N-busbar can be automatically and permanently connected by simply pushing on the screwless N-disconnect slide link. This approach cuts down on wiring; the N-conductor is only supplied once per RCD potential and distributed via the N-busbar.
The multilevel installation terminal blocks with internal disconnect, in contrast, are suitable for smaller circuit groups with multiple RCD potentials.
The advantage of this alternative is that it saves space on the DIN-rail by omitting busbars. Since no short N-busbar sections for numerous different ground fault potentials are needed, installation effort is also reduced.

Practical Tips for TOPJOB®S Rail-Mount Terminal Blocks

How does PV system connection work? How do rail-mount terminal blocks work in distribution boxes? How do distribution cabinets work with TOPJOB®S Rail-Mount Terminal Blocks?

Applications in PV Systems

WAGO’s TOPJOB® S Rail-Mount Terminal Blocks connect PV lines reliably and permanently. Disconnect and fuse terminal blocks with high voltage resistance securely isolate PV generators from inverters. Custom-engineered solutions, such as diode boxes up to 1000 VDC, complete the system.

For example, 6 mm2 (10 AWG) and 16 mm2 (6 AWG) terminal blocks can be easily commoned using a step-down jumper.

WAGO’s range of TOPJOB® S Classic 780 to 784 Series Rail-Mount Terminal Blocks directly connect voltages up to 1000 VDC and VAC. With an intelligent jumper program, the TOPJOB® S Rail-Mount Terminal Block System also permits PV lines to be easily bundled and routed to the inverter with a larger conductor cross-section.

TOPJOB® S Rail-Mount Terminal Blocks (2006, 2010 and 2016 Series) are rated at 800 V, permitting operation in pollution degree 3 environments. However, a common potential can be achieved by commoning individual terminal blocks. The remaining clearance and creepage distances from potential to DIN-rail are sufficient for 1000 V applications. Separating the common potential blocks, e.g., by an end stop, is all that is required. At higher voltages, a partial discharge test is recommended as a further test in addition to simply taking the clearances and creepage distances into account.
This is why at WAGO, the product series for use in photovoltaic systems undergo partial discharge tests to verify the long-term stability of the insulation material on the individual components and terminal blocks.

Practical Tips for the Multifunctional Jumper Range

What’s the best way to use jumpers?

The TOPJOB® S Rail-Mount Terminal Blocks include a comprehensive multifunctional range of jumpers for all conceivable commoning tasks. The following two examples illustrate the flexibility of adjacent jumpers and push-in type jumper bars in realistic practical situations.

Adjacent jumpers for continuous commoning provide flexibility for changes.

Example 1: Unlimited Commoning

WAGO’s 2002 Series Continuous Jumpers readily connect an unlimited number of terminal blocks to each other. The jumpers are designed so that a contact for two jumpers can be placed in one jumper slot, providing a common contact. This means that only one jumper slot of the TOPJOB® S Rail-Mount Terminal Blocks is required for continuous commoning. The second jumper slot can be used for additional commoning, accommodating TOPJOB® S Connectors for additional connections or for testing. For any additional function, or commoning a greater number of terminal blocks during commissioning, simply add another continuous jumper. Removing individual jumpers from the assembly is just as easy. This way, you can common any number of terminal blocks with a single product.

Yet another advantage is that continuous jumpers can be used to common any number of terminal block function groups. Only one jumper is needed to connect 2, 3, 4 or n terminal blocks. Here too, changes can be made flexibly.

Example 2: Commoning via Step-Down Jumpers and Push-in Type Jumper Bars

One WAGO Pro Power Supply with 24 V powers several loads, in this case eight, through a single electronic fuse. The loads’ neutral conductors are connected to the blue TOPJOB® S Neutral Conductor Terminal Blocks. In this example, two four-conductor Series 2001 Terminal Blocks are used. A two-conductor TOPJOB® S 2004 Series Rail-Mount Terminal Block is used to link the loads’ negative poles to a power supply.

The 2001 Series (nominal cross-section: 1.5 mm2/16 AWG) and the 2004 Series (nominal cross-section: 4 mm2/12 AWG), which is two cross-sections larger, can be commoned with a standard 2001 Series 3-Way Push-in Type Jumper Bar (Item No. 2001-403). The last jumper contact can be inserted into the jumper slot of the 2004 Series. Commoning over the end plate is also possible.

Therefore, the TOPJOB® S Rail-Mount Terminal Block system allows terminal blocks differing by up to two nominal cross-sectional sizes to be commoned using a simple push-in jumper bar from the smaller series. Nonetheless, it is important that the total current of the outgoing circuits not exceed the nominal current of the push-in type jumper bar.

WAGO’s TOPJOB® S jumper line also offers the right solution for all other commoning tasks. Star and delta jumpers are available for star or delta motor connections. Pluggable vertical jumpers can easily connect all the levels within multilevel terminal blocks. Staggered jumpers allow you to accommodate four potentials alongside each other. Potentials with different spacing and heights can also be easily commoned using push-in type wire jumpers.

Expert Interview on Rail-Mount Terminal Blocks in Building Distribution Cabinets

Safe and economical conductor connection is what electrical interconnection technology is all about. Although it sounds incredibly simple, it actually places extremely high demands on the components used. In this interview, WAGO Product Manager Andreas Brettschneider explains what really matters when it comes to engineering rail-mount terminal blocks for use in building distribution cabinets.

Mr. Brettschneider, what are the main demands placed on interconnection technology for switchgear in today’s buildings?

Well, the biggest demands are cost-efficiency and safety. The first requirement is met by fast installation. This is why push-in termination is preferred for connecting the solid conductors that are primarily used in buildings. We provide that with our Push-in CAGE CLAMP® Connection Technology within the TOPJOB® S Rail-Mount Terminal Block family.

And what about safety?

WAGO’s rail-mount terminal blocks feature high safety reserves. For example, this means that our rail-mount terminal blocks can be wired one size over their rated cross-section. They can also be loaded with the rated current of the next largest cross-section. Some concrete numbers: A 2.5 mm2 (14 AWG) conductor can be accommodated in a terminal block with a nominal cross-section of 1.5 mm2 (16 AWG). This results in additional cabinet space savings.

But what about problems related to heating effects?

These effects pose no problem at all. In fact, heating effects must be accounted for when planning and designing switchgear and control cabinets. And this has been required by the IEC 61439 standard for low-voltage switchgear and control gear assemblies since late 2014. Therefore, the relevant question is actually what the electrical reserves of components are. Due to their large electrical reserves, our TOPJOB® S Rail-Mount Terminal Blocks have a minimal impact on heating effects for switchgear and control cabinets.

Does this mean that the TOPJOB® S Rail-Mount Terminal Blocks range offers different advantages for cabinet design and installation?

Exactly. Both cabinet planners and manufacturers benefit from large electrical reserves and a compact terminal block design. This allows a higher number of terminal blocks to be accommodated in distribution cabinets, while satisfying demands for more building wiring. Furthermore, on-site electricians also benefit from our Push-in CAGE CLAMP® technology that allows quick, reliable termination of solid conductors in building circuits during distribution cabinet wiring.

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