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Electricity is an area in which everything must be done correctly and thoroughly. In this regard, many prefer to figure it out on their own, rather than trust strangers. One of the key points is the connection of wires in the junction box. Firstly, the correct operation of the system depends on the quality of work, and secondly, safety – electrical and fire.
What is a junction box
From the electrical panel, the wires diverge through the premises in the house or apartment. In each room, as a rule, there is more than one connection point: there are several sockets and a switch for sure. To standardize the methods of connecting wires and assemble them in one place, junction boxes are used (they are also sometimes called branching or junction boxes). Cables from all connected devices are brought into them, the connection of which takes place inside the hollow body.
In order not to look for wiring during the next repair, it is laid according to certain rules that are prescribed in the PUE – Rules for the Installation of Electrical Installations.
One of the recommendations is to conduct all connections and branches of wires in the junction box. Therefore, the wires are allowed along the top of the wall, at a distance of 15 cm from the ceiling level. Having reached the branch point, the cable is lowered vertically down. A junction box is installed at the branch point. In it, all the wires are connected according to the required scheme.
According to the type of installation, junction boxes are internal (for flush mounting) and external. A hole is made under the internal ones in the wall, into which the box is built. With this installation, the cover is flush with the finishing material. Sometimes during the repair process it is covered with finishing materials. However, such installation is not always possible: the thickness of the walls or finishes does not allow. Then a box for outdoor mounting is used, which is attached directly to the wall surface.
The shape of the junction box can be round or rectangular. There are usually four conclusions, but there may be more. Conclusions have a thread or fitting, to which it is convenient to attach a corrugated hose. After all, it is more convenient to lay wires in a corrugated hose or a plastic pipe. In this case, it will be very easy to replace the damaged cable. First, disconnect it in the junction box, then from the consumer (socket or switch), pull and pull it out. Tighten a new one in its place. If you lay it the old fashioned way – in a strobe, which you then cover with plaster – you will have to hollow out the wall to replace the cable. So this is the recommendation of the PUE, which is definitely worth listening to.
What do junction boxes generally give:
- Increased maintainability of the power supply system. Since all connections are accessible, it is easy to identify the area of damage. If the conductors are laid in cable channels (corrugated hoses or pipes), it will also be easy to replace the damaged section.
- Most electrical problems occur in the connections, and in this installation option, they can be inspected periodically.
- Installing junction boxes increases the level of fire safety: all potentially dangerous places are in certain places.
- Requires less money and labor than laying a cable to each of the outlets.
Wire connection methods
In the box, the conductors can be connected in different ways. Some of them are more difficult, they are implemented, others are easier, but if executed correctly, they all provide the required reliability.
Scrolling
The most popular method among craftsmen, but the most unreliable. It is not recommended by the PUE for use, as it does not provide proper contact, which can lead to overheating and a fire. This method can be used as a temporary one, for example, to check the operability of the assembled circuit, with a mandatory subsequent replacement with a more reliable one.
Even if the connection is temporary, everything must be done according to the rules. The methods of twisting stranded and solid conductors are similar, but have some differences.
When twisting stranded wires, the procedure is as follows:
- the insulation is stripped 4 cm;
- conductors unwind by 2 cm (pos. 1 in the photo);
- are connected to the junction of non-untwisted conductors (pos. 2);
- the veins are twisted with fingers (pos 3);
- the twist is tightened with pliers or pliers (pos. 4 in the photo);
- insulated (duct tape or heat shrink tubing put on before the connection).
Connecting wires in a junction box with one core using twisting is easier. The conductors, cleared of insulation, are crossed and twisted with fingers along the entire length. Then they take a tool (pliers and pliers, for example). In one, the conductors are clamped near the insulation, the second is strenuously twisted the conductors, increasing the number of turns. The junction is isolated.
Twisting with mounting caps
Twisting is even easier using special caps. With their use, the connection is more reliably insulated, the contact is better. The outer part of such a cap is molded from flame retardant plastic, a metal conical part with a thread is inserted inside. This insert provides a large contact surface, improving the electrical performance of the connection. This is a great way to connect two (or more) wires without soldering.
Twisting wires with the help of caps is even easier: the insulation is removed by 2 cm, the wires are slightly twisted. A cap is put on them, it is turned with effort several times until the metal is inside the cap. Everything, the connection is ready.
Caps are selected depending on the cross section and the number of conductors to be connected. This method is more convenient: it takes up less space than conventional twisting, everything fits more compactly.
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If there is a soldering iron in the house, and you know how to handle it at least a little, it is better to use soldering. Before twisting, the wires are tinned: a layer of rosin or soldering flux is applied. A heated soldering iron is dipped in rosin, and carried out several times over the part stripped of insulation. A characteristic reddish coating appears on it.
After that, the wires are twisted as described above (twisting), then the tin is taken to the soldering iron, the twist is heated until the molten tin begins to flow between the turns, enveloping the connection and ensuring good contact.
Installers do not like this method: it takes a lot of time, but if you do the connection of the wires in the junction box for yourself, take the time and effort, but you will sleep peacefully.
wire welding
If there is an inverter welding machine, you can use the welding connection. This is done on top of the twist. Set the welding current on the machine:
- for section 1,5 mm2 about 30 A,
- for section 2,5 mm2 – 50 A.
The electrode is used graphite (this is for welding copper). With grounding pliers, we carefully cling to the upper part of the twist, we bring the electrode to it from below, briefly touch it, achieving the ignition of the arc, and remove it. Welding takes place in a fraction of a second. After cooling, the junction is isolated. The process of welding wires in the junction box, see the video.
Terminal blocks
Another connection of wires in the junction box is using terminal blocks – terminal blocks, as they are also called. There are different types of pads: with clamps and screw, but, in general, the principle of their device is the same. There is a copper sleeve / plate and a wire attachment system. They are designed so that by inserting two / three / four conductors into the right place, you connect them securely. In installation, everything is very simple.
Screw terminal blocks have a plastic housing in which the contact plate is fixed. They are of two types: with hidden contacts (new) and with open ones – the old model. In any of them, a conductor stripped of insulation (length up to 1 cm) is inserted into the socket and clamped with a screw and a screwdriver.
Their disadvantage is that it is not very convenient to connect a large number of wires in them. The contacts are arranged in pairs, and if you need to connect three or more wires, you have to squeeze two wires into one socket, which is difficult. But they can be used in branches with significant current consumption.
Another type of blocks is Vago terminal blocks. These are fast mounting pads. Two types are mainly used:
- With flat spring mechanism. They are also called disposable, since their reuse, if possible, is with a significant deterioration in the quality of contact. The point is in the internal structure: in the case there is a plate with spring petals. Inserting the conductor (only single-core), the tab is bent, clamping the wire. Providing contact, it cuts into the metal. If the conductor, with due effort, can be pulled out, then the petal will not take its former shape. Therefore, this type is considered disposable. Despite this, the connection is reliable, and you can use them. There are also special terminal blocks of the same shape, but in a black case. They contain electrical paste inside. These connectors are necessary if you have to connect copper and aluminum, which simply do not fit together due to the active electrochemical processes that occur between them. The paste prevents oxidation, allowing the two metals to fuse easily.
Terminal blocks Vago - Universal with lever mechanism. This is perhaps the most convenient connector. Insert the bare conductor (the length is written on the reverse side), press the small lever. The connection is ready. If necessary, remake the contact, lift the lever, remove the wire. Comfortable.
The peculiarity of these terminal blocks is that they can only be operated at low currents: up to 24 A with a copper wire cross section of 1,5 mm, and up to 32 A with a cross section of 2,5 mm. When connecting loads with high current consumption, the wiring in the junction box must be connected in a different way.
Crimping
This method is possible with special pliers and a metal sleeve. A sleeve is put on the twist, it is inserted into the pliers and clamped – it is pressed. This method is just right for lines with a large ampere load (like welding or soldering). See the video for details. It even has a junction box model assembled so it will be useful.
Basic wiring diagrams
Knowing how to connect the wires in the junction box is not all. It is necessary to figure out which conductors to connect.
How to connect sockets
As a rule, the socket group is a separate line. In this case, everything is clear: you have three cables with three (or two) conductors in your box. Coloring can be the same as in the photo. In this case, usually brown is the phase wire, blue is zero (neutral), and yellow-green is ground.
In another standard, the colors may be red, black and blue. In this case, the phase is red, blue is neutral, green is ground. In any case, the wires are assembled by color: all of the same color in one group.
Then they are folded, stretched, cut to be the same length. Do not cut short, leave a margin of at least 10 cm so that you can remake the connection if necessary. Then the conductors are connected by the chosen method.
If only two wires are used (there is no grounding in the houses of the old building), everything is exactly the same, only there are two connections: phase and neutral. By the way, if the wires are of the same color, first find the phase (with a probe or multimeter) and mark it, at least by winding a piece of electrical tape on the insulation.
With a switch, the matter is more complicated. There are also three groups, but their connection is different. Eat
- input – from another junction box or from the shield;
- from a chandelier;
- from the switch.
How should the circuit work? Power – “phase” – goes to the switch key. From its exit is fed to the chandelier. In this case, the chandelier will only light when the switch contacts are closed (position “on”). This type of connection is shown in the photo below.
If you look carefully, this is how it turns out: the phase with a light wire enters the switch. It leaves from another contact, but already blue (do not mix it up) and connects to the phase wire that goes to the chandelier. Neutral (blue) and ground (if mains) are twisted directly.
Connecting a two-gang switch
Connecting the wires in the junction box with a two-gang switch is a little more complicated. The peculiarity of this circuit is that a three-core cable must be laid to the switch for two groups of lamps (in the circuit without grounding). One wire is connected to the common contact of the switch, the other two are connected to the key outputs. In this case, it is necessary to remember what color the conductor is connected to the common contact.
In this case, the phase that has arrived is connected to the common contact of the switch. The blue wires (Neutral) from the input and the two bulbs are simply twisted all three together. There are wires left – phase from the lamps and two wires from the switch. So we connect them in pairs: one wire from the switch to the phase of one lamp, the second output to another lamp.
Once again about connecting wires in a junction box with a two-gang switch in video format.