Terminal block: fixing wires in electrical circuits

Any electrician will call a short circuit the most common wiring fault. Broken contacts are found a little less often. However, this is a consequence, and the reason is hidden in the weakened interaction between the conductors. To avoid this, there are several ways to strengthen them, one of which is to install a connecting terminal block at the branch of the network.

Types of core switching and defects

Contact between live parts is one of the elements of the electrical circuit. In order to link the components together, there is Several variants:

• Ordinary twisting, not allowed by the Electrical Installation Rules, but in practice it is used quite often. In old houses, PPE caps are installed to bring it in line with the PUE standards, ensuring reliable soldering. True, they can only be mounted on products made of homogeneous metals, usually copper.
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• Soldering or welding requiring special equipment and skills. This technique is used when installing low-current systems with cables made of the same materials.
• The use of connector blocks for wires will be optimal in terms of ease of use and compliance with standards. With their help, it is possible to switch conductors made of any metals.

Despite the variety of ways to connect cables, they have requirements for reliability and safety. The main parameters are as follows:

• Maintainability.
• Availability for control.
• High strength.
• Guaranteed resistance not exceeding 1.2 times the entire core.
• Long service life and invariability of physical characteristics during this period.

However, during operation, when the conductors interact, an inevitable electrochemical reaction occurs. As a result such problems may occur:

• Loosening and oxidation of contact.
• Power outages.
• Heating at the point of interaction (often leads to a fire).

As a result, the most suitable for installation in any conditions, especially at home, are electrical connectors.

Basic requirements for the design of terminal blocks

Now in stores you can buy many varieties of similar products. Regardless of belonging to one type or another, any switching device must meet certain conditions:

• Non-flammable housing to prevent a fire hazard in the event of a rise in temperature as a result of poor contact.
• The protective covers are made of the same flame retardant material.
• The strength of the product must be sufficient to hold it in place when tightening the screws.
• Reliable fastening of cable ends without tinning, making rings or crimping terminals.
• Preventing the connected wires from touching each other to avoid oxidation (in the case of copper-aluminum).
• Clear, easy-to-read marking with data on conductor cross-section, maximum permissible current and voltage.

Pads classification

There are several types of such devices. All of them do their job well - to provide reliable contact in the cable connection. There are several categories into which they are subdivided.

Body material

This part is made from non-conductive raw materials. Another mandatory requirement is the selection of the minimum distance between the points of contact to exclude air breakdown. The shell of the connection terminal block can be:

• Ceramic, installed in places with high temperatures. These products include heating elements, power connections. Do not install such components under vibration and shock loads, they are too fragile.
• Polypropylene switches are durable and flexible, do not crack when deformed. However, due to their low temperature and dielectric characteristics, their installation in high-voltage installations with a phase or zero located close to each other is not allowed. The exception is lighting networks.
• Pads made from durable flame retardant polyamide are quite expensive. They are used where increased requirements are imposed on the equipment.
• The carbolite terminal blocks have the best strength and insulation characteristics. Their use is permissible everywhere, except for heating devices.
• Products made of polyvinyl chloride are widely used in low-current connections, household appliances and lighting. This is the cheapest option. However, due to the fact that PVC melts when heated, they must be used with caution. Another advantage of such terminal blocks is the convenient form of release in the form of blocks. Thus, any number of permanent connections can be selected.
• Textolite or ebonite parts are rare due to their high cost.

Wire fastening method

For screw terminal blocks, this can be a classic slip-on design or clamping. The first is the connection of the nut, the role of which is played by a threaded contact plate, and the screw. In this case, the end of the wire must be prepared: a ring is formed or a ferrule is installed. They are used for installation in junction boxes.

For pads of the second type, the device provides for fixing a simply stripped core. This is possible due to the special design of the nut. It forms a kind of clamp, tightened with a screw to the block. The disadvantage of such a product is that the core is under constant pressure, which destroys metal, especially aluminum.

A common negative side of such terminal blocks is the need for constant monitoring of the reliability of fastening and periodic tightening of contact groups.

The quick-clamping pads are devoid of this flaw. They are disposable or reusable. Vago products are a typical example of such products.

Despite the fact that the contact in them is less dense, the popularity of such structures is growing, especially with large volumes of installation work. The speed of laying networks using such clamps is much higher compared to screw clamps.

Switch mounting type

The simplest terminal block consists of a housing, a metal rail and a number of clamps. One block is designed to connect either phase or zero (ground). When choosing a retainer, it is necessary to take into account the method of its installation. There are many types of switching devices:

• The screws already described earlier.
• Detachable, one part of which is in contact with the conductor, and the other with the board. Installed on microcircuits.
• Push-on or spring-loaded.
• Barrier designed for power plants.
• Pass-throughs, allowing you to connect several wires of different metals to create branched electrical circuits.
• Stackable, mounted on DIN rails. Fixation takes place with the help of latches that prevent the pads from falling out of the block.

Installation features

The installation of the terminal blocks is simple and does not require special training. It is only necessary to select a product that corresponds to the diameter of the wire, and insert conductors stripped by 5-7 millimeters into it. It is not recommended to use aluminum cables for screw blocks due to the possibility of pinching the wire.

If absolutely necessary, tighten such contacts with the utmost care. Such a metal has increased fluidity, which implies a gradual weakening and complete loss of contact.

Therefore, it is recommended that such connections be revised annually to prevent heat build-up and fire.

Positive and negative sides

Electrical terminal blocks are widely used due to positive feedback on their use. Among the advantages are the following:

• Ease of connecting the maximum number of conductors of different cross-section and metal. Each of them is located in a separate slot and can be removed without disassembling the entire structure. If you use any other method, then the wires will have to be switched again.
• High-quality insulating materials provide the required level of safety, eliminating electric shock when touching the interface.
• No special tools are required to work. All you need is a screwdriver and a knife.
• Resistant to temperature fluctuations and mechanical stress (stretching or vibration).
• Aesthetic appearance.
• Compact dimensions.

Among the shortcomings, a rather high price stands out, which affects large volumes of installation. However, with the development of technology, this defect is gradually disappearing. The work of installing terminal blocks in hard-to-reach places will be quite time consuming. But this applies to any of the common ways of connecting cables. An inconvenience is the regular control over the quality of contact in the case of using screw shoes.

Manufacturers of electrical products

The choice of the model by the end customer very strongly depends on the manufacturer. The quality of the materials used plays an important role in the manufacture of terminal blocks. Therefore, it is best to make a choice in favor of well-known manufacturers.

Legrand Company

The pads of this company are made of brass with a nickel layer. This allows you to increase the reliability of the contact and increase the conductive properties of the product. The body is made of polypropylene with an operating temperature range of -25 to +100 degrees Celsius and resistance to open fire. Legrand's products owe their popularity to the following qualities:

• High strength of the pads.
• Wide range of sizes up to 25 sq. mm.
• Application both in power and low-current electrical circuits for industrial and household purposes.
• Multilevel quality control at every stage of production.
• A variety of colors allows you to distinguish between conductors of unequal denominations.

Reliability of switching can be ensured if a number of installation and operating conditions are observed. Among them are such requirements:

• Exclude the touch of conductors from different materials inside the device.
• Minimize mechanical and vibration loads during use of the pads.
• Regular broaching of connections.

Vago products

The popularity of terminal blocks from WAGO Kontakttechnik GmbH & Co. KG, founded in 1951. in Germany, growing every year. Its first developments were spring pads, in the production of which the Germans became the undisputed world leaders. In 1973 g. small-sized products for installation in junction boxes were patented and introduced to the market.

The main advantages of the switches of this company are:

• High vibration resistance.
• Minimal pressure on the wires, which reduces their deformation and destruction.
• International product certification.
• Tinned copper tires are corrosion protected.
• High resilience austenitic steel springs.
• For the manufacture of the shell, a modified polyamide is used, which is resistant to inflammation, corrosive liquids and has the ability to self-extinguish.

There are two types of Wago terminal blocks on sale. This is one-piece Puch Wire with a rigid spring. They can be used for solid conductors or stranded conductors with ferrules. There are also reusable Cage Clamps available.

In order to install the Vago terminal block, you need to follow simple steps:

• Strip the insulation of the wire by 10-13 mm.
• Insert it into the block. It is more convenient to do this with pliers.

The terminals of the German manufacturer can provide from 2 to 8 seats for cores with a diameter of 0.5-4 sq. mm. The voltage used is 220 volts, the maximum current is 32 amperes. This is sufficient for home electrical applications.

Other manufacturers

In addition to the most well-known companies among professionals, there are no less respected manufacturers of electrical commutation pads. Among them are:

• The German company Phoenix Contact, which produces goods of appropriate quality at an affordable price.
• Weidmüller specializes in automation blocks. Terminal blocks for DIN rails are on a special account.
• The Chinese Degson Electronic and Wanjie Electronic have a good reputation in the domestic market.
• Russian representatives of the industry also have good reviews, but the products have an unreasonably high price, and the quality of the materials used leaves much to be desired.

The reliability of connections in electrical engineering is ensured by products from advanced raw materials and a modern manufacturing process. Compliance with regulations and the use of the best components ensures safe and trouble-free operation of the entire electrical circuit for a long time.