Electricity is so familiar in modern life that it is almost impossible to imagine how to manage without it. If you can wash or grind the meat by hand, then television, the computer, the mobile phone on coals, as the iron, will not earn. Electricity in every home is a necessity, and it is supplied there by wires from external networks. At the entrance to each apartment or individual house there is a junction box, from which the wires of the internal electrical wiring run.
- 1 Junction box need
2 Wire Connection Methods
- 2.1 Twist
- 2.2 Solder or weld joint
- 2.3 Pressure testing
- 2.4 Connecting Isolation Clamps (PPE)
- 2.5 Bolted connections
- 2.6 Screw clamps
- 2.7 Nut clamp
- 2.8 Terminal blocks
- 2.9 WAGO terminals
- 3 Wire connection in junction box
Junction box need
First of all, junction boxes provide fire safety. The greatest danger in terms of the occurrence of fire are the junction of wires. Due to the large resistance in places of insufficient tight contact, heating of the wiring in this place occurs, which can cause a fire when in contact with combustible materials of the wall.
The junction box eliminates the risk of fire by isolating the junction of the wires.
In addition, the junction box plays a functional role. Access to the wire connections hidden in it is much easier and more convenient than if the connection of each the wires were hidden in the wall in the deep grooves that needed to be opened, breaking the wall decoration, during repair wiring.
And even outdoor junction box looks aesthetic compared to a bundle of cables sticking out of the wall.
Wire Connection Methods
Special Rules for the Installation of Electrical Installations (PES) regulate the proper connection of electrical conductors by welding, soldering, crimping or using screw and bolt clamps.
Rules do not specify the most common method of connection - twisting. Although the correct twist is more reliable than a bad solder joint. Choosing a connection method depends on several factors:
- connecting materials. This may be aluminum, copper, or a combination thereof;
- the number of wires in the connection. It is possible to connect not only two, but also three, four and more wires;
- load on the circuit;
- section and number of veins.
To make such a connection, you need clean the ends of the lived, carefully twist them with pliers and insulate the place of twisting. Very simple and without material costs. But such a compound weakens with time due to the residual elastic deformation of the material, a, This means that resistance in the joint increases and the contact begins to warm up to destruction and fire Therefore, in no case should you lay the wiring with a twist on the combustible base, for example, in a wooden house. And another prohibition - weak protection against moisture does not allow such a connection to perform in rooms with high humidity.
In this way it is strictly forbidden to connect dissimilar materials, stranded cables with single core and with a current greater than 3 A.
To twist was high quality, with wires you need remove insulation up to 80 mm length wires, fold them perpendicular to each other, if there are two, and in parallel, if there are three or more, and twist tightly. The remaining ends of the wires need to be removed with a screw motion with a nipper, as if joining the material of the wires into one another. The total length of the finished twist must be at least ten, and preferably fifteen diameters of the wires.
If special caps or heat shrink tubing (cambric) are used for insulation, they are put on the wire before twisting. It is recommended to wear the shrink tube twice, and to put the insulating tape in at least three layers. Whichever insulation material is chosen, it must also seize its own insulation of the wires to protect it from moisture and creep.
Solder or weld joint
This method is best for a combination of manufacturability and reliability, but requires some skill to perform a quality connection.
Before soldering, the wires must be thoroughly cleaned of insulation and oxides, tinned if necessary and not twisted as tightly as with a simple twist, covered with flux and soldered. Soldering can be used to connect copper and aluminum wires with suitable flux and solder. You cannot use the active acid flux, as it breaks the connection, remaining on the bare wires. Isolates the junction in the usual way.
With undeniable merits, this method has quite significant drawbacks:
- the need for skills in the work, the complexity of the process;
- use of special tools;
- permanent connection, that is, for repair it must be completely removed;
- increase with time of resistance in the connection, which impairs the electrical conductivity and increases the voltage loss in the network.
Welding - even more reliable connection methodthan soldering, but you need a welding machine with individual protective equipment and welding skills, which is much less common in everyday life. Unless you need to independently perform electrical work in a country house, then the acquisition of an inverter-type welding machine will be economically justified. Welding inverters are compact, have a wide range of welding current control, and with low power consumption they provide stable arc burning. For welding copper wires, carbon-copper electrodes or carbon rods from conventional finger batteries are used.
Preparation for welding differs only in the density of twist and the fact that the free ends of two veins, even if more in the joint, straightened and pressed parallel to each other to facilitate the formation of a ball melt. Then the twist is placed in a welding clamp (ordinary old pliers) and the ends of the wire are welded with a carbon electrode to the main twist for two to three seconds so that the insulation does not melt. After cooling, the place of welding isolate in the usual way.
Often there is a temptation not to wait for natural cooling, but to use cold water to speed up the wiring process. But cold water causes microcracks in the material, which naturally affects the quality of the connection.
With this method of connecting electrical wires, special tubular sleeves or tips are used. The industry produces sleeves for wires with a cross section of 2.5 to 240 mm², and it is very important to choose the right connector for a particular connection. To perform the work required special tool. It can be a pressing press or pincers, mechanical, electrical or hydraulic.
Having chosen a suitable sleeve and adjusting the tool, remove the insulation from the wires, trim the ends and apply quartz-petroleum jelly paste on them, put on the connector and press out. If the tool is simple, then you need to perform several reductions at some distance from each other. Using a good tool, you can compress the sleeve at one time. At the end, the usual joint isolation is performed.
The connected wires can be inserted into the connector from opposite sides so that their joint is approximately in the middle of the sleeve. It may be convenient to insert both wires on one side, and the total cross-sectional area of all wires must be less than the cross section of the sleeve. High-quality installation and reliable insulation - these are the positive aspects of using crimping. But There are negative points:
- the sleeve is deformed during pressure testing and its repeated use is impossible;
- the need for a special tool for crimping the liner, adjusting its length and removing the insulation from the wire;
- for crimping the connection of copper and aluminum wires need a rather rare special sleeve;
- quite a lot of time for the installation of electrical wiring.
Connecting Isolation Clamps (PPE)
The clamp represents square steel wire caprolled into a spiral cone. For aluminum wires, the cone is filled with a special paste that prevents the oxidation of bare ends. Correctly choose the size of PPE in accordance with the cross-sectional area and the number of connected conductors will allow the information on the package with clips.
To connect the wires, their ends are trimmed at a distance of a little less than the depth of the cap, put together, slightly twisted and the top is wrapped around the cap. It is not necessary to strip bare wires from oxides, since this work is performed by the edges of the spring, and its turns tightly press the wires to each other.
The use of such connectors is technologically advanced; they not only connect the wires, but also insulate the junction, however, they do not provide that contact area, as when twisting with soldering. The bright colors of the caps help to mark the installation with zero, phase and grounding if the wires are not color-coded. The disadvantages include:
- gradual weakening of the spring with time, and, consequently, an increase in contact resistance and voltage losses in the network;
- restrictions on the number of connected wires, you can connect two with a cross section of 4 mm² or four with a cross-sectional area of 1.5 mm²;
- the impossibility of mixed compounds.
Bolt connection is a simple, reliable and efficient way. You just need to have a short bolt of a small section, three washers and a nut. True, the tape on such a connection takes a lot, and in the junction box is not used because of the bulkiness. They put a washer on the bolt, then twist the stripped wire, another washer (if copper and aluminum are connected), the second wire, the washer and tightly tighten the nut.
Screw clamps allow you to perform quick and neat installation. They are widely distributed when connected to the wires of lamps, switches, sockets. They can be used to connect copper and aluminum, without the need to isolate the connections.
The disadvantages of screw clamps include:
- the need to crimp or propayki stranded cable before installation;
- the need for periodic maintenance of connections, as the screws need to be tightened, that is, they need access.
This connector was named for the form. It is a cable clamp with special plates, in which grooves for wires are made, and four screws at the corners. Wires are stripped, inserted under the plate and fixed with screws. Then the carbolic shell is put on. With this clamp you can combine copper and aluminumThe insulation is reliable enough, the installation process is simple and easy. Basically, such a side connection is used to divert to apartments from a common aluminum riser. But in addition to tightening the threaded connections, there is another drawback - dimensions, because of which the "nut" does not fit in the junction box.
Connection using terminal blocks is used in junction boxes, when installing fixtures, sockets and switches. Terminal blocks are small in size, fit easily in a box. A brass bushing is inserted into a small plastic case into which screws are screwed in from both sides. From the ends of the pads, stripped veins are inserted and tightened with screws. For wires of different sections are designed pads with a different inlet. The quality of such a connection is high, the installation is easy, dissimilar materials can be joined, but there are also significant disadvantages of terminal blocks:
- connecting only two wires;
- poor quality of the pads themselves, which can cause network disturbances;
- Care must be taken when installing aluminum and stranded wires so as not to damage the contact due to the brittleness of the metal.
This relatively new type of connection using spring insulated clamps is by far the most reliable and secure. Disputes over the reliability of connections using WAGO terminals can be associated either with counterfeit on the market or with the wrong choice of terminal for a particular load. International certificates and approvals protect the reputation of these products. Their only drawback is high price.
A special screwless spring mechanism makes the installation of connections simple and quick. The terminals can be reusable with a special lever, which clamps the wire and releases it if necessary. One-time terminals fix the core with some effort, but, according to the manufacturers, it is impossible to release it.
For installation, you only need to strip the ends of the wires and insert them into the clip.
Advantages of WAGO terminals:
- possibility of mounting dissimilar metals;
- the possibility of fixing at the same time more than two wires;
- accurate fixing of thin wires;
- good connection quality;
- compact size.
Wire connection in junction box
Of all the above methods of connecting wires in the junction box, the “nut” and the bolted connection are not used for one reason - large dimensions. All other methods have the right to life.
It remains to clarify two points, what method should be used to connect a large (three, four, five) number of wires and what to do if you need to connect wires of different cross sections.
WAGO terminals or a cheaper option are well suited for connecting wires of different cross sections. ordinary terminal blocks. But for a large number of conductors in the junction box, you can use several options depending on the conditions and cost of installation:
- WAGO terminals;
- pressure testing;
Naturally, it is preferable to use WAGO terminals, and at the very least - twisting.
When choosing a solution, it is necessary first of all to ensure the safety and reliability of operation of electrical networks, and then durability and cost follow. And it is very important that the wiring connections, no matter how they are made, are available for inspection and maintenance.