Ways to securely connect wires

Recommendation points

• Connection of wires in junction boxes
• Crimping of wires
• Crimping conductors
• Soldering wires
• Welding
• Connecting wires to terminals of electrical equipment
• Practical advice for switching electrical wires

In the article, we will talk about ways to connect wires in junction boxes, talk about preparing conductors for connecting household appliances and installation products.

The electrical wiring of residential premises consists of many elements, these are various current-carrying conductors (cables), protective devices, wiring accessories, and individual current consumers. In order to assemble all the components of the system into a single circuit and at the same time make the power supply functional and safe, it is necessary to connect them to each other with high quality, or, as they say, to connect them (switching refers to the processes that occur when electrical circuits are closed or opened).

At first glance, it may seem to an untrained person that nothing complicated should be here. But, working with an electrician “on a whim”, it does not matter whether we transfer a single socket, connect a lamp or assemble a complex control system, we are at serious risk. Experienced electricians know that wiring is primarily a “fight for contact”, since it is an open circuit, and not a short circuit, that is the most common problem that one has to face. Obviously, the places of connections in the circuit (terminals, twists) are the most vulnerable, since at these points the mechanical contact density can weaken (the contact area decreases), an oxide film with a very high resistance forms on the conductors over time. Poor contact becomes the reason for the heating of current-carrying conductors, sparking at the points of commutation – these are the consequences of the appearance of a transient contact resistance. Complete burnout of the wire and de-energizing the site when household appliances do not work, or the light goes out, this is unpleasant, but the problem is solved. Worse, if the insulation of the wires heats up and collapses, which threatens a person with electric shock or fire.

Recently, the load on the wiring has seriously increased, therefore, even more stringent fire and electrical safety requirements are now imposed on switching. However, if earlier there were not many connection options, now there are reliable modern devices that facilitate wiring switching. In addition to welding and soldering with subsequent strip insulation of the twist, PPE caps, various terminal screw and spring blocks, all kinds of insulated and open lugs, branch clamps can be used in the household network. These products will help to qualitatively connect wires in junction boxes, assemble a switchboard, connect household appliances and lighting fixtures, sockets and switches.

There are several key objective factors that influence the choice of the switching method, or the use of specific devices. Let’s just list the main ones:

• power and number of consumers (read: total conductor cross-section);
• material of current-carrying conductors (copper or aluminum);
• type of cables (flat or round, rigid or soft stranded, single or double insulation);
• node designation (group or single branch, end connection);
• the presence of mobility of wires or vibrations near them;
• high temperature, humidity;
• indoor or outdoor use.

Connection of wires in junction boxes

According to the provisions of the PUE, the branching of the wires of the household network can only be made in the distribution (junction) box. Junction boxes allow, during the operation of the wiring, to quickly reach the ends of any individual branch, if necessary, to find out which of them is broken or has a short circuit. You can also always inspect the condition of the contacts inside the box, perform their maintenance. Modern PVC boxes are used for open and hidden wiring, they have sufficient reliability and extended functionality: they are easily installed on various surfaces, convenient for electrical manipulations.

In order to always have access to the connected wires, all junction boxes are located on free sections of the walls; it is most rational to install them from the side of the corridors, for example, above the door of a powered room. Naturally, the boxes cannot be plastered tightly, or sewn up inside building frames, the permissible decorative maximum is a thin-layer finish over the lid (paint, wallpaper, decorative plaster).

For arrangement of lighting and power circuits (outputs and sockets), it is recommended to use separate junction boxes for each room. Such a split power supply makes it possible to make the electrical wiring of the home more balanced and safe, since “light” and “sockets” differ in terms of workloads and operating conditions, they have different requirements. Moreover, it is much easier to upgrade or repair the wiring later, and not always all the wires of a room can be normally marked in one case..

The commutation of wires in any junction box can be carried out according to the same principle. In most cases, “twisting” is initially used, but simply wrapping conductors with electrical tape is not enough – it must be reinforced with additional operations that are designed to increase the contact area of ​​the connected current-carrying conductors and reduce the oxidation of materials. Clause 2.1.21 of the PUE offers the following options:

• soldering
• welding
• crimping
• crimping (bolts, screws, etc.)

Crimping of wires

The essence of this method lies in the fact that twisted wires are inserted into a special sleeve made of metal, which is compressed with hand pliers, a mechanical or hydraulic press. Pressing can be done either by local pressing or by solid pressing. This wire connection is considered one of the most reliable. Crimping allows the conductors to be compressed very tightly, increasing the contact area, the mechanical strength of such commutation is the highest. This method is applied to both copper wires and aluminum.

The crimping process consists of several operations, each of which has its own nuances:

1. The wires are freed from insulation by 20-40 mm from the edge, depending on the working length of the sleeve.
2. The veins are cleaned with a brush or emery to a shine.
3. Tight twisting is done with pliers.
4. According to the total cross-section of the twisting, a GAO sleeve with the required inner diameter is selected, as well as a suitable punch and matrix.
5. The liner is processed from the inside with quartz-vaseline paste (if it comes from the factory “dry”).
6. The twist is inserted into the sleeve.
7. The stranding is compressed with press tongs. It is necessary that the tooling of the tool is completely closed.
8. The quality of the connection is checked – the wires should not move in the tip.
9. The sleeve of the connected conductors is wrapped with electrical tape in three layers, with a tip thickness of up to 9 mm, a polyethylene insulating cap can be used.

Crimping conductors

Crimping conductors can be done using terminal blocks, PPE caps or WAGO clamps.

The terminal block housing is made of plastic, inside it there are sockets with threads and clamping screws. The wires can be wound under single terminal screws towards each other, or one conductor goes through the entire block and is fixed with two screws. Some junction boxes are assembled with standard strips.

A clear advantage of switching on the terminal block is the ability to connect copper and aluminum wires, which in this case do not have direct contact. The disadvantage is the need to tighten the bolt clamp if aluminum conductors are used.

The PPE caps (connecting insulating clamps) are also made of durable non-flammable polymer, which, being an insulator, provides mechanical and fire protection. They are wound with effort on the twisting of the conductors, then the conical metal spring inside the cap expands and compresses the current-carrying conductors. As a rule, the internal cavity of the PPE is treated with a paste that prevents oxidation.

WAGO clamps for junction boxes are screwless, here the compression is performed by a spring, you only need to insert the stripped wire into the terminal. These terminal blocks are designed to connect up to eight wires with a cross section of 1–2.5 mm² or for three conductors with a cross section from 2.5 to 6 mm², the spring acts on the conductor with a force suitable for each conductor. The clamps function normally at operating currents up to 41 A for 6 squares, 32 A for 4 squares and 25 A for 2.5 squares. Interestingly, WAGO universal clamps allow you to connect wires of different cross-sections (from 0.75 to 4 mm²).

These devices can be designed for a rigid conductor, or for a soft stranded conductor. Due to the fact that there is no direct contact of the wires to be connected, copper and aluminum wires can be switched, while there is no need to regularly revise the aluminum compression. Inside, WAGO terminal blocks also have a paste that destroys the oxide film and improves contact, however, the clamps for copper conductors are not filled with contact paste. It is very easy to work with such connecting products, they are quickly installed, without the use of additional tools, they are compact and reliable. It must be said that WAGO is not the only company that produces screwless spring-loaded terminal blocks..

Whichever type of crimping device is used, it is necessary to accurately select it according to the section of a separate conductor or twisted, since a terminal that is too large may not provide normal contact. In this case, you can not always trust the marking – it is better to check the conformity of the fasteners and conductors on site. We recommend having an assortment of crimp terminals by standard size during installation. Please note that contact gel must be used to work with aluminum; copper and aluminum conductors cannot be connected in one twist. After crimping, it is always necessary to check the tightness of fixing the cores in the terminal.

Soldering wires

Due to the technological complexity, this connection method is used quite rarely, mainly when, for some reason, it is impossible to use crimping, crimping or welding. You can solder aluminum and copper conductors, you just need to choose the right solder. For branching wires up to 6-10 mm² an ordinary soldering iron is suitable, but more massive wires will have to be heated with a portable gas torch (propane + oxygen). For soldering, it is necessary to use a flux in the form of rosin or its alcohol solution.

The advantages of soldering are considered to be the high reliability of the connection, compared with crimping (in particular, we have an increased contact area). Also, this method is quite inexpensive. The disadvantages of switching building wires by soldering include the duration of work, the technical complexity of the process.

The soldering of the conductors is as follows:

• wires are stripped of insulation;
• the veins are sanded with emery to a metallic sheen;
• twisting is made 50–70 mm long;
• the core heats up with a burner flame or a soldering iron;
• the metal is covered with flux;
• solder is introduced into the working area or a hot twist is immersed in a bath with molten solder for 1–2 seconds;
• after cooling, the brazed twist is insulated with electrical tape or polymer caps-tips.

Welding

Most often, electricians use contact heating to reliably switch wires in a junction box. You can weld twisting with a total cross-section of up to 25 mm². Under the action of an electric arc at the end of the twist, the metal of several strands is fused into a single drop, and then the current during the operation of the electric circuit flows not even through the body of the twist, but through the formed monolith. If everything is done correctly, then the connection turns out to be no less reliable than a solid wire. This method has no technological and operational drawbacks, the only thing is that you need to purchase a suitable welding machine.

Welding of copper conductors is carried out with direct or alternating current with a voltage of 12 to 36 V. If we talk about factory welding units, it is better to use inverter devices with sensitive adjustment of the welding current, which are light and lightweight (during operation, they are sometimes worn on the shoulder) , can be powered from a household network. In addition, inverters provide good arc stability at low welding currents. Due to the high cost of inverters, electricians very often use home-made welding machines made from a transformer with a power of more than 500 W, with a secondary voltage of 12–36 volts. The earth and the electrode holder are connected to the secondary winding. The electrode itself for welding copper conductors must be infusible – carbon, this is a factory copper-plated “pencil” or a homemade element made of a similar material.

If a factory inverter is used for welding wires, then it is recommended to set the following operating current indicators for conductors of different cross-sections: 70-90 amperes is suitable for connecting two or three wires with a cross section of 1.5 squares, wires with a cross section of 2.5 mm² welded at 80-120 amperes. These indicators are indicative, since the exact composition of the core may vary from manufacturer to manufacturer – it is recommended to test the device and a certain current strength on wire cuttings. Correctly selected indicators are when the arc is stable, and the electrode on the twist does not stick.

The wire welding process includes the following operations:

• the conductors are stripped of insulation (about 40–50 mm);
• a tight twist is made with pliers, its end is cut so that the ends of the wires have the same length;
• a mass clamp is connected to the twist;
• the carbon electrode is brought to the end of the twist for 1-2 seconds (so that the insulation does not melt, but a solid copper ball forms;
• after cooling, the welded twist is insulated with electrical tape, heat shrink tubing or a plastic tip.

When connecting wires, you should observe safety precautions and take fire-fighting measures, as for any welding work. It is recommended to use a welding mask or special glasses with a light filter, welding leggings or gloves will not be superfluous.

Connecting wires to terminals of electrical equipment

Connecting household appliances and various wiring products is also an important step in wiring. The performance of consumers, as well as the protection of users and fire safety, depends on the reliability of electrical connections in these nodes..

The technology for connecting current-carrying conductors to equipment is regulated by the PUE, current SNiPs, as well as “Instructions for the termination, connection and branching of aluminum and copper conductors of insulated wires and cables and their connection to the contact terminals of electrical devices.” Just like the branching of conductors in junction boxes, soldering, welding, crimping, screw or spring crimping are used for termination and connection. One way or another is chosen primarily depending on the design of the equipment, as well as on the properties of the current-carrying conductor.

Screw crimping is used in most types of modern equipment. There are screw terminals in sockets and switches, chandeliers and lamps, in various household appliances (built-in fan, air conditioner, hob). Crimp sockets are supplied to the elements of the switchboard: circuit breakers, RCDs, electric meters; here, switching buses with screw terminals are used.

It should be noted that the convenient spring-loaded terminal blocks can also be used to connect equipment. For example, very often switches are equipped with screwless terminals, WAGO produces a special series of clamps for connecting chandeliers and lamps, as well as for switching in ASU (terminals installed on a DIN rail).

Please note that soft stranded conductors must be terminated with insulated ferrules (connectors) for crimp connections. Connectors are not required for rigid monolithic conductors. If you do not use ferrules, then the soft core should be twisted tightly and coated with solder before connecting. The size of the tip is selected depending on the cross-section of the conductor, and the geometry of the contact part – depending on the type of terminal on the connected device and the features of operation. For example, for a clamping tunnel socket, a connector in the form of a pin is used, for fixing with a nut on a bolt – a ring or fork. In turn, the forked tip is not recommended for use if the device is movable or vibration is possible in the switching zone.

If it is necessary to clamp a rigid single-wire conductor (copper or aluminum) with a cross section of up to 10 mm under the bolt², it can be bent into a ring of a suitable radius using round-nose pliers. The ring is cleaned from the oxide film with glass cloth or emery paper, lubricated with quartz-vaseline gel and put on the bolt (the ring should wrap the bolt clockwise), after which it is covered with an asterisk washer (prevents the conductor from being squeezed out), a grover (springs the connection, does not allow to unwind when vibrations) and the assembly clamp is tightened tightly with a nut. If a large cross-section core (from 10 mm²), then by pressing a metal sleeve with a ring.

Practical advice for switching electrical wires

Switching wires is a very responsible job, while the process of assembling a circuit has a lot of nuances, which for convenience should be combined into one list:

1. Strip the wires with special pliers, since when removing the insulation with a knife, the cross-section of the core often decreases.
2. Always remove the oxide film from the conductor. Use glass skin or emery, use special fluids and contact paste.
3. Twist a couple of centimeters longer, and then cut off the excess.
4. Select the diameter of the sleeve or tip as accurately as possible.
5. Run the conductor under the terminal or sleeve / lug up to the insulation.
6. Make sure that the wire insulation does not get under the clamp.
7. If possible, wind and clamp not a single soft core into the tunnel screw terminal, but a twisted one.
8. Using electrical tape, wind it with an overlap of turns in three layers, be sure to go to the insulating sheath of the conductor. Electrical tape can be replaced with heat shrink or plastic caps.
9. Be sure to wrap the screw terminal blocks with electrical tape.
10. Always check the tightness of the connection mechanically – pull on the conductors.
11. Never connect copper and aluminum directly.
12. Firmly fasten the cable near the patching area so that the wire does not pull downwards and the connection is not subjected to any mechanical stress.
13. Use the color-coded conductors, for example, in the entire intra-house network, the brown conductor will be the phase, blue will be zero, yellow will be the ground.
14. Accept a single connection diagram for the installation of all devices (for example, the phase on the sockets is clamped on the right terminal, and the neutral – not on the left).
15. Mark both ends of all wires yourself – with a ballpoint pen on the outer sheath, at a distance of 100–150 mm from the edge of the conductor, write its purpose (for example, “pink kitchen desktop” or “light bedroom”). You can also use tags or pieces of masking tape.
16. Leave a supply of wires convenient for installation. For junction boxes, sockets and switches, the normal end length will be 100-200 mm. To switch the board, you may need wires up to one meter long, so that you can wind some of them from the bottom of the box, and some from the top.
17. Bring the external cable ducts to the junction boxes close, it is better to lead a round corrugation or pipes into the housing a few millimeters.
18. We connect the sockets in parallel, and the switches in series. The switch must break the phase, not zero.
19. Squeeze all wires of one switched twist into a bundle and fix it with electrical tape. Inside the box, separate the insulated connections as far apart as possible..
20. Use only certified materials and specialized tools.

In conclusion, I would like to reiterate the importance of high-quality switching work. In fact, the technologies used are quite simple, you just need to make them a habit, and then the “installation culture” will appear by itself, and the wiring will be reliable and durable.