Terminal blocks
(3 026)Terminal blocks, due to their simplicity and convenience of use, are commonly used by electricians in almost every electrical installation. Mostly located in junction boxes, control cabinets and switchgears, they are used for the safe connection of electrical wires. A very convenient solution is to use the so-called connection terminal when mounting lighting elements. The use of a terminal block will enable quick disassembly when a lamp needs to be replaced or during renovation. The principle of operation, construction, and purpose of terminal blocks will be discussed below.
The simple design of terminal blocks
A terminal block, also called as connection terminal or terminal connector, is made of a properly selected material, ensuring safety and isolation of live conductors from the elements of the junction box. It also separates the individual electrical wires from each other, ensuring that there is no short circuit in the system. It allows you to achieve any pole count that is needed and easily connect multiple wires. Depending on the needs of the installer, the terminal block has an appropriate number of poles (the only limitation is the amount of space available at the installation site) intended for connecting wires with different cross-sections. Terminal blocks come in single housings with greater mechanical strength or can be constructed in pieces that are interlocked with one another to form more complex connection systems. The modular solution has a very significant advantage. The use of different colors in a system can be used as a visual guide for wiring.
These elements, thanks to their small size and ease of assembly and disassembly, provide convenient access to connections and enable effective modifications to electrical installations.
The simplest terminal block type has one input and one output contact where wires are fed and the signal is transmitted inside the housing. PCB terminal block has a distinctive design. It connects electronic components using conductive paths printed on a board by means of appropriate contacts. Such products are widely used in all kinds of electronic systems. The wire is secured by a clamping screw and the signal is transmitted using a crimp pin connector. The principle of operation is the same in both cases. The only difference is that with the PCB connector the signal is transferred to the board, not to the other wire.
Terminal block mounting
Depending on the available space and mounting options, the terminal blocks are mounted as follows:
- Fitted with mounting holes;
- DIN-rail mounting;
- PCB snap-on mounting;
- Cable or panel mounting.
How to choose the right terminal block
The most important parameters to pay attention to when selecting a terminal block are:
- Rated current and voltage - The temperature of the wire insulation increases as the current intensity increases. It is important that, in the case of a terminal strip, an increase in this temperature does not result in overheating and consequent melting of the housing material. Such a situation could lead to damage to the connecting element and/or the installation. The temperature resistance , rated voltage, and current efficiency, which should be 1.5 times the maximum current supplied to the load, is specified by the manufacturer for each terminal block. In particular, the following are responsible for meeting these requirements: body material and contact material;
- Wire gauge;
- Number of connection ways - depending on the needs, terminal blocks with the required number of ways are used. Due to the modular design and the possibility of snapping multiple pieces together, it is not necessary to install excessively long terminal blocks "just in case".
- Contact pitch - The distance between adjacent contacts that constitutes the safe insulation distance. They prevent the individual current circuits from directly influencing each other.
Due to the standardized diameters of conductors in electrical cables, the most commonly used areterminal blocks with the following spacings: 2.5 mm, 4 mm, 6.3 mm, 10 mm, and 16 mm, but non-standard sizes are also available. Therefore, in a properly stocked store, you can obtain the type of terminal block you are interested in.
The connection terminals available in the catalogue are suitable for installations with parameters within the following ranges:
- Cable cross-sections - 0.5 ÷ 95 mm2;
- Rated current - 6.3 ÷ 232 A;
- Number of ways - 1 ÷ 12.
A very important parameter characterizingterminal blocks is the method of fastening and securing the wire in the housing. The following design solutions are distinguished:
- Screw terminal - the electric wire located in the housing is tightened with a screw that fixes its position and prevents it from sliding out;
- Spring clamp - automatically allows the wire to be pressed directly into the housing;
- Push Button - pressing the button opens the spring clamp and allows you to insert the wire into the terminal insertion hole or remove it. Releasing the button, on the other hand, clamps the wire and prevents unwanted release.
Standards for terminal blocks
In accordance with the legislation in force, auxiliary equipment in the electrical engineering sector, including terminal blocks, shall be subject to applicable national and European standards (PN-EN) and comply with IEC (International Electrotechnical Commission) standards. Compliance with the standards confirms the high quality of products and compliance with the required safety standards. An example of such a standard is PN-EN 60947-7-1:2012, which specifies the requirements for terminal blocks intended for industrial or similar use and to be fixed to a support.
The most important advantages of using terminal blocks
- The use of terminal blocks enables connecting shorter wire lengths, which reduces costs and replacement time in the event of failure (e.g. mechanical);
- Easy mounting;
- If it is necessary to disconnect the circuit again, the wires are not damaged;
- Safe to use;
- They guarantee a tight connection and no transmission interference.
Terminal blocks for professionals and amateurs
After reviewing the guidelines for the selection of the appropriate terminal block, even an inexperienced DIY enthusiast should have no problems with using it in a distribution board or a junction box and connecting electrical systems with the so-called connection terminal. Any modifications to electrical installations will also not result in the loss of a damaged cable or a hole punched in the wall. The wide range of products available is good enough for the most demanding industrial and domestic electrical installations. Therefore, when preparing to modify or create a new electrical installation, it is worth allocating relatively small funds for the purchase of terminal blocks and arming yourself with high-quality connecting elements.
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