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Terminal Blocks: Over the last several years, manufacturers of terminal blocks have noted the following trends: increased usage of screwless connection systems; increasingly compact, multi-functional terminals; and integrated accessories. How is Siemens responding to those trends?

Over the last several years manufacturers of terminal blocks have noted the following trends:

• Increased usage of screwless connection systems, i.e. Spring Loaded, Push-in and Insulation Displacement, leading to installed time savings. 

• Toward increasingly compact, multi-functional terminals.

• Integrated accessories (leading to less inventory and shorter parts lists)

In response to these trends Siemens has expanded existing and added new terminal block lines.  Siemens product offering now includes five connection types. They are:     

• 8WA1 Terminals with Screw Connection

• 8WA2 & 8WH2 Terminals with Spring Loaded Connection

• 8WH3 Terminals with Insulation Displacement Connection

• 8WH4 Terminals with Plug-in Connection

• 8WH5 Terminals with Combination Plug-in Connection

8WA1 Terminals with Screw Connection

The terminal body is designed in such a manner that the tensile stresses that occur when tightening the conductor clamping screws causes the terminal block body to deform elastically.  This compensates for any creeping of the clamped conductor.  The deformation of the screwed part prevents the clamping screw from loosening, even under heavy mechanical and thermal stresses.  Solid, stranded and finely stranded conductors can be safely and permanently clamped.

Siemens line of globally accepted screw-type terminal blocks also have the following advantages:

• Are insulated on both sides and closed at both ends removing the need for end plates and eliminates the costs and inventorying of additional parts.

• Have a symmetrical design making alignment of the terminals unnecessary before mounting on standard 35 mm mounting rails.

• Allows usage of conductor sizes in the range of 22 AWG (0.2 mm²) through 500 kcmil (240 mm²) depending on the terminal block selected.

• Are available in 16 versions.

8WA2 and 8WH2 Terminals with Spring Loaded Connection

The spring loaded clamp is opened by inserting a screw driver or other similar operating tool.  The conductor is then inserted as far as possible into the spring clamp and held in place after pulling out the screwdriver.  Solid, stranded or finely stranded conductors can be safely and permanently clamped. 

The trend towards spring loaded terminal blocks is on the rise, especially in the construction of electrical panels, systems, controls and transport systems.  The main advantage of the spring loaded connection is that the spring always exerts constant pressure on the conductor, independent of the operator’s influence.  There is no need to check the connection.

Siemens line of spring loaded terminal blocks are primarily intended for vibration sensitive applications and:

• Have extremely compact designs which ensure very user-friendly wiring, even where space is at a premium.

• Have convenient connections which are made from the top of the terminal block ensuring that the conductors are securely connected to the power bus.

• Allow usage of conductor sizes in the range of 28 AWG (1.5 mm²) through 2 AWG (35 mm²) depending on the terminal block selected.

• Are available in standard or compact designs in 19 versions.

8WH3 Terminals with Insulation Displacement Connection (IDC)

The IDC clamp cuts into the conductor insulation on two sides making contact with the wire. By inserting a screw driver or other similar operating tool, and the conductor, into their respective guides and pushing or pulling the operating tool forward or backward the wire insulation is penetrated by the IDC clamp establishing a secure contact with the wire.

Siemens line of insulation displacement terminal blocks is intended for use in applications where time savings is of most importance; allowing up to 60% time savings because it is not necessary to strip the conductor.  Other product features include:

• Protection against corrosion.

• Mounting without special tools

• Usage of conductor sizes in the range of 22 AWG (0.25 mm²) through 14 AWG (2.5 mm²) depending on the terminal block selected.

• Availability in 5 versions.

8WH4 Terminals with Plug-in Connection

Solid conductors or conductors with end sleeves are simply pushed into the wire guide of the terminal block.  This is the main feature of “plug-in” connections.  A screwdriver is only used to remove the conductor from the terminal block.  This is the same wiring technology that was used to wire the wall switches and plug-in receptacles in your home or apartment.  The plug-in connection is particularly advantageous in very narrow and tight wiring applications.

Siemens line of plug-in terminal blocks include:

• Ddirect connection of rigid conductors.

• Connection of stranded conductors with wiring sleeves.

• Loosening by screw driver (no other tool actions are required).

• Usage of conductor sizes in the range of 24 AWG (1.5 mm²) through 8 AWG (6 mm²) depending on the terminal block selected.

• Availability in 3 versions.

8WH5 Terminals with Combination Plug-in Connection

This contact system consists of two parts; terminal block and plug.  The plug is wired separately from the terminal block and at final assembly the plug is “plugged into” the terminal block.  Both the plug and terminal block use familiar screw or spring loaded connections and can withstand the most extreme vibration demands.

Combi plug-in terminals are used anywhere where pre-assembled modules are used or a high degree of modularity is needed.  They also include:

• High contact stability during vibrations.

• Finger safe design to prevent human contact with live electrical parts

• Usage of conductor sizes in the range of 22 AWG (0.25 mm²) through 10 AWG (12 mm²) depending on the terminal block selected.

• Availability in 5 versions.