Wire connection. Description of Connection Methods
How to connect the wires? This question at least once in a life each man was set, even without being the electrician. In everyday life, we often have to deal with similar issues. The plug of the electric cable fell off, the chandelier wire broke, the socket stopped working, the connection in the home phone was lost, there is no voltage in the vehicle’s on-board network, etc. It’s easy to solve all these problems if you have basic electrical engineering knowledge and repair work.
In this article, we will look at how to properly make the connection of wires when installing electrical wiring, breaking an electrical circuit, or simply for the purpose of repairing electrical engineering.
Why can not directly connect wires from different metals
To begin with, it is impossible to just take and connect the conductors, not taking into account the properties of the material from which they are made.Each of the metals used to transmit electricity, and this is most often aluminum, copper and steel, has a different density, resistance and conductivity. In addition, it is necessary to take into account such factors as the electrochemical potential arising from the effect of current on the metal.
Serious problems, for example, can cause incorrect connection of copper and aluminum wires. This issue is often faced by professionals involved in the repair of wiring in our homes. The fact is that in most of the old houses and apartments wiring from copper wire is laid. Indeed, about 30 years ago, copper was cheap, but by electrical indicators it is significantly superior to aluminum.
Today, copper wires are used quite rarely. Their place was taken by aluminum.
But what happens if you still connect copper with aluminum? The latter, being a metal with a high oxidation rate, forms on its surface a specific film with a sufficiently high electrical resistance. This is especially evident when exposed to moisture.
Copper also has a similar film, but its resistance is much less.Because of this difference, the direct connection of copper and aluminum wires causes obstructed conductivity, and reciprocal oxidation processes lead to the formation of shells on the conductors, heating, sparking, and even fire.
But what about when it is necessary to connect the wires from different metals? For this there are special devices. We will talk about them now in the context of a review of existing types of compounds.
- Twisting (twisting).
- Pressure testing.
- Terminal connection
- Connection with terminal strips and clamps.
- Threaded connection.
- Connection by puncturing the conductors.
- Cable squeeze.
- Connection with the "nut".
Twist - this is the easiest connection of wires. It is enough to strip them out of isolation, tightly twist together with the help of pliers - and you can experience. Yes, such installation has the right to exist, but not for a long time, especially if we are dealing with different materials of conductors. It can only be used as a temporary connection and should be replaced with a more reliable one at the slightest opportunity.By the way, this installation is not mentioned at all in the rules for electrical installation (PUE), as it is considered unreliable and rather dangerous.
Such a connection of wires is categorically not recommended for installation or repair of electrical networks, electrical wiring in the room and the car.
But there is a reliable twist, or rather, an improved one. VMS caps are on sale that are specifically designed to increase the reliability of twisting. They are made of fireproof plastic, and inside they have a tapered spring. Placing the usual twist inside such a cap, it must be turned to the stop. The coils of the spring under the influence of your strength will open, and then securely fix the ends of the conductors together. The cap at the same time will get the role of a kind of electrical insulator. This method is often used to ensure the connection of wires in the distribution box of a dwelling or industrial premises.
Banding is also one type of twist. It is not very reliable and cannot be recommended for installation or repair of electrical wiring.
The essence of the banding is that the bare ends of two, three or more conductors fold together and are wrapped with a softer wire with good conductivity, for example, copper with zinc coating, after which the place of contact is carefully insulated.
Next, we analyze the more reliable types of wire connections. One of these installations is the welding of electrical conductors. It can be called an improved and legalized twist, because the ends of the wires after twisting are subject to welding. This process can be carried out in two ways: by means of electric arc welding and thermite. In the first case, metal electrodes are used, and in the second - a special combustible mixture.If everything is clear with arc welding, then we will consider in more detail how the installation is carried out with the help of thermite powder.
There are special thermite cartridges of various diameters, inside of which there is a pressed combustible mixture. It consists of crushed aluminum, magnesium, calcium, silicon, titanium and other metals. This powder is burned with a huge amount of heat.Under its influence, the conductors, being placed in such a cartridge, are firmly welded to each other. To get a similar connection of wires, you just need to strip them out of isolation, twist, place the twist inside the cartridge and burn it with a special match that is included in the kit. After welding, it is necessary to remove slag deposits, which are formed as a result of burning.
Naturally, by welding it is possible to make the connection of wires and cables only of large diameter. For domestic needs, this method is not intended.
Another fairly common, but not very reliable way of installation is soldering. It is best suited for use in everyday life, unless we are talking about electrical wiring. According to GOST R 50571.5.52-2011 and PUE, this connection method is not recommended for high voltage electrical circuits, since the solder has a rather low melting point. But for the repair of household electrical appliances, it is quite suitable.
Immediately you need to indicate that this method can only make a connection of copper wires, since aluminum at home can hardly be soldered.
In order to qualitatively carry out the soldering, you will need:
- 60-100 W soldering iron;
- solder (tin-lead);
- flux (rosin);
- small brush (for applying flux);
We clean the wires by 3-4 cm, we process the sandpaper and twist them together. Now, using a brush, apply flux to the compound and solder the wires to each other, applying molten solder.
If our wires are stranded, pre-twist each of them and cover them with solder.
Sometimes it is necessary to connect not two, but three, four or more conductors. Of course, there is no need to do without special devices, however, for circuits using low voltage, you can apply the installation called “star”. This is a kind of solder twist of several conductors. The star connection of the wires consists in winding a spiral onto the main conductor of the taps, followed by covering the contact points with solder and insulating.
Crimping is one of the most reliable types of connection and meets all the requirements of electrical installation rules. Its essence lies in the fact that the wires are placed in a special metal sleeve and crimped with a special tool.
It’s enough to have:
- an appropriately sized sleeve of copper or aluminum (the material must match the material of the conductors);
- knife to remove insulation;
- special press tongs (pliers are not suitable);
- insulating tape.
We clean the wires to the length of the sleeve, twist it and place it in the sleeve. Then, using ticks, we press on our joint and isolate it for safety.
There are also special sleeves-tubes for longitudinal connection, i.e. extension of the conductor. In this case, the wires are inserted on both sides of the tube, after which each of them is crimped separately.
Such a connection of electrical wires is widely used in the installation of electrical wiring in residential and industrial premises.
This method can not boast of its popularity, but its reliability is beyond doubt. Here, as a connecting element, a special rivet is used, which, in fact, is needed in order to securely connect the conductors by riveting. The material of the rivet - copper or aluminum is chosen under the material of the wires.
This scheme of connecting wires is often used when installing and repairing consumer electrical networks 380/220 V.
To connect the conductors by riveting, you will need:
- rivet (copper or aluminum);
- two steel washers (flat and spring);
- special tool - riveter.
The rivet is first put on the end of one wire, which is stripped and twisted into a ring, then a spring washer, after it - a similarly processed and formed end of another wire and a flat washer.
Further, this assembly assembly is placed in the riveter. The master can only squeeze his handle until it clicks, notifying that the installation is ready, then make the insulation.
Terminal connection is most common in automotive electrical circuits, where it is often necessary not just to connect wires, but to connect them to some device, be it a relay, a sensor, a backlight, etc., having for this purpose special standardized contacts. Its essence lies in the fact that the desired size of the terminal is put on the end of the wire stripped of insulation, after which its lower part is pressed together with ordinary pliers. For more reliable contact, the junction can be soldered.
Terminal strips and clamps
Installation using “terminal blocks” is probably the most common way to connect household electrical wiring wires.There is no need for welding, soldering, or special tools. It is enough to have special “terminal blocks” for connecting the wires, sold in any hardware store for a penny, and an ordinary screwdriver. Such an installation is very reliable and durable.
"Terminal blocks" for connecting wires are of two types:
- with bolt clip;
- self-tightening with spring clip.
The first option involves the use of a plastic terminal strip with contacts clamped with bolts. To carry out such installation, you need to unscrew the screw with a screwdriver, insert the wire into the hole specially provided for it and clamp it in the same way.
Self-tightening terminal blocks are even easier to operate. Their design is equipped with a flat spring mechanism, actuated by special levers on the body. It is enough to cock this lever, insert the end of the stripped wire under it and release. The spring itself will clamp the wires and securely fix them.
These methods of connecting wires have virtually no flaws, except for one - the quality of the materials from which they are made. You probably remember the old Soviet terminal strips made of solid non-combustible black plastic.Today they are often found in old electrical wiring and are ready to serve for decades to come. Modern "terminal blocks" can not boast of this, so when buying, pay special attention to the material of the case and do not purchase cheap models.
Threaded connections of wires are most often used in various input and distribution devices of electrical installations. This installation is reliable enough and also does not require any special skills. As a connecting element, a conventional steel bolt is used here. The ends of the wires after stripping are formed into eyelets and are put on the bolt leg interspersed with steel washers so that between them, as well as on both sides of the conductors, is along the washer. After this, the construction is clamped with a nut.
This installation is advantageous in that it allows the connection of aluminum wires used in consumer power lines and copper, as well as their combinations.
There is another type of installation that is used exclusively for power lines, various electrical installations and their distribution devices. This is a piercing.It is carried out with the help of a special piercing clamp, which is put on the conductors and, compressing them, cuts off the insulation, forming contact between the conductors.
Its advantage over other methods is the possibility of installation without turning off the power line, because the master does not have direct contact with the conductor itself.
Cable clamp allows not only to connect two conductors of different metals, but also to create a side branch from them. It consists of two steel plates, flat or with special bulges to the cable diameter, connected with several bolts. After opening these bolts, bare wires of conductors are inserted between the plates in a certain order. Upon completion of installation, the bolts are clamped, holding the wires firmly. With the help of such plates it is possible to compress and conventional twisting, significantly increasing its reliability.
Nutlet is an enhanced version of cable squeeze. Its design also provides for the use of two figured plates pressed together by bolts. However, the "nutlet", among other things, has a collapsible body in the form of a plastic ball, which is put on the connection after the installation is completed.This feature allows you to use this connection in the open.
Some useful tips
- When connecting the wires intended for high voltage transmission independently, observe at least the first two of the three rules of the electrician: “Disconnect, check, ground”.
- Choosing the type of connection, stop at the most reliable and secure.
- Never use fittings such as twisting or banding to connect wires outside.
- Each connection must be reliably insulated.
- Having no idea about electrical engineering, do not try to repair the electrical grid or electrical appliance with your own hands, it’s better to rely on experts.