Wire connection methods: soldering, welding, terminals, clamps

When wiring or repairing electrical wiring, when connecting household appliances and a lot of other work, it is required to connect conductors. In order for the connection of wires to be reliable and safe, it is necessary to know the features of each of them, where and when, under what conditions they can be used. 

Existing methods of connecting conductors

To connect the wires can be done in several ways:

• welding is the most reliable method, providing high reliability of the connection, but requiring skills and the presence of a welding machine;
• terminal blocks – a simple and fairly reliable connection;
• soldering – works well if the currents do not exceed the normative ones and the connection does not heat up to temperatures above the norm (65 ° C);
• crimping with sleeves – requires knowledge of technology, special pliers, but the connection is reliable;
• the use of spring clips – wago, PPE – quickly installed, subject to operating conditions provide good contact;
• bolted connection – easy to perform, usually used in difficult cases – if it is necessary to switch from aluminum to copper and vice versa.

The specific type of connection is selected based on many factors. It is necessary to take into account the material of the conductor, its cross section, the number of cores, the type of insulation, the number of conductors to be connected, as well as the operating conditions. Based on these factors, we will consider each of the types of connections.

Welding – high reliability in all conditions

When connecting wires by welding, the conductors are twisted, and their end is welded. As a result, a ball of metal is formed, which provides a stable and very reliable connection under any conditions. Moreover, it is reliable not only in terms of electrical characteristics, but also mechanically too – the metal of the connected wires after melting forms a monolith and it is impossible to isolate a separate conductor.

The disadvantage of this type of wire connection is that the connection is 100% one-piece. If you need to change something, you need to cut off the fused piece and redo it all over again. Therefore, for such connections, a certain margin of wires is left – in case of a possible alteration.

Other disadvantages include a welding machine, appropriate electrodes, flux and work skills. In addition, welding takes a lot of time, it is necessary to protect surrounding objects, and it is also inconvenient to work with a welder at a height. Therefore, electricians practice this type of connection in exceptional cases. If you are doing “for yourself” and know how to handle a welding machine well, you can practice on scraps. The trick is not to melt the insulation, but to weld the metal.

After cooling, the welding site is isolated. You can use electrical tape, you can use heat shrink tubing.

Crimping connection of wires

For crimping wires, a special aluminum or copper sleeve is required – it is selected based on the size of the twist (bundle diameter), and the material is taken the same as that of the conductors. The wires that are bare and cleaned to a shine are twisted, a tube-sleeve is put on them, which is clamped with special tongs.

Both sleeves and pliers are different, there are several types. Each of them has its own rules of use (the number of wires that can be packed into a sleeve), in which you need to be well versed. It is necessary to pack the wires according to certain rules, measure the size of the resulting bundle, and adjust it to the requirements. All in all, a pretty tedious job. Therefore, this type of wire connection is mainly used by professional electricians, and even more often they switch to spring clips.

Terminal blocks

One of the simplest and most reliable wire connections is through terminal blocks. There are several types, but almost everywhere a screw connection is used. There are sockets of different sizes – for different sizes of conductors, with a different number of pairs – from 2 to 20 or more.

The terminal block itself is a plastic case in which a metal socket or plate is soldered. A bare conductor is inserted into this socket or between the plates, clamped with a screw. After the screw is tightened, it is necessary to pull the conductor well – make sure that it is well clamped. Due to the fact that the connection points remain uninsulated, the scope of the terminal blocks is rooms with normal humidity.

The disadvantage of this connection is that due to the plasticity of metals – especially aluminum – the contact weakens over time, which can lead to an increase in the degree of heating and accelerated oxidation, and this again leads to a decrease in contact. In general, the connection of wires in screw terminal boxes must be tightened periodically.

Advantages – speed, simplicity, low cost, does not require any skills, except perhaps the ability to use a screwdriver. Another important advantage is that you can easily connect wires of different diameters, single-core and stranded, copper and aluminum. There is no direct contact, therefore there are no risks.

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First, about soldering technology. The connected conductors are cleaned of insulation, cleaned of oxide film to bare metal, twisted, then tinned. To do this, the conductors are heated with a soldering iron, applied to rosin. It should cover the junction completely. Tinned wires are twisted first with fingers, then squeezed using pliers. Soldering flux can be used instead of tinning. They wet the wires well, but after twisting.

Then, in fact, the soldering process begins: the junction is heated with a soldering iron or a narrow-torch burner. When the rosin or flux begins to boil, take some of the solder on the soldering iron tip, bring it into the soldering area, pressing the tip against the conductors. The solder spreads out, filling the gaps between the wires, making a good connection. When using a torch, the solder is simply added little by little to the torch.

Further, after the soldering place has cooled down, according to the technology, it is necessary to wash off the flux residues (they accelerate oxidation), dry the joint, cover it with a special protective varnish, and then insulate it with electrical tape and / or heat shrink tubing.

Now about the advantages and disadvantages of this method of connecting wires. In low-current systems, soldering is one of the most reliable ways to connect wires. But, when wiring electrical wiring in a house or apartment, it is criticized mercilessly. The fact is that the solder has a melting point of 195-210 degrees. With the passage of high currents, the connection heats up, (if circuit breakers are incorrectly selected or faulty), the solder melts and solidifies. After repeated repetitions, the solder runs off or becomes porous, impairing contact. Time after time, the contact gets worse, the connection heats up more and more. If this process is not detected, it may well end in a fire.

The second negative point is the low mechanical strength of soldering. The point is again in tin – it is soft. If there are a lot of wires in a soldered joint, and if they are still rigid, when trying to pack them, the conductors often fall out of the solder – the elastic force that pulls them out is too great. Therefore, the connection of conductors by soldering when distributing electricity is not recommended for use: it is inconvenient, long and risky.

Spring terminals for connecting wires

One of the most controversial ways to connect wires is with spring clamps. There are several types, but the most common two are wago terminal blocks and PPE caps. Externally and by the method of installation, they are very different, but both designs are based on a spring that creates a strong contact with the wire.

There is controversy about this spring. Opponents of using wago say that the spring will weaken over time, the contact will become worse, the connection will start to heat up more and more, which, again, leads to an even faster decrease in the degree of elasticity of the spring. After some time, the temperature may rise so much that the case (plastic) will melt, but what can happen next is known.

In defense of the use of spring clamps for connecting wires, if they are used in accordance with the manufacturer’s recommendations, problems are very, very rare. Although there are many fakes of both wago and PPE, as well as an abundance of pictures of them in a melted form. But, at the same time, many use them, and, under normal operating conditions, they work for years without any complaints.

Clips for wires wago

They appeared on our market a few years ago and made a lot of noise: with their help, the connection is very fast and easy, while it has high reliability. The manufacturer has specific recommendations for the use of this product:

• wago can only be used for solid or stranded conductors with a cross section of 0,5 mm or more² up to 4 mm²;
• for fixing and connecting stranded and small-diameter wires, use the CAGE CLAMP clamp – from 0,08 mm² up to 35 mm²;
  

Inside these devices there is a metal plate, which provides the proper degree of contact. The shape and its parameters of the plates were developed and tested specifically. The tests were carried out on a vibration stand for many hours, then heated-cooled. After that, the electrical parameters of the connection were checked. All tests were passed as “excellent” and branded products always show themselves as “five”.

In general, the Wago product range is very wide, but for wiring or connecting household appliances, lighting fixtures, two types of wire clamps are used: the 222 series (detachable) with the ability to remake or change the connection and the 773 and 273 series – which are called one-piece.

Detachable

Spring clamps for electrical wiring Wago 222 series has a certain number of contact pads – from two to five – and the same number of flags-clamps. Before starting the connection, the flags are raised up, the conductors stripped of insulation are inserted into them (up to the stop), after which the flag is lowered. At this point, the connection is considered complete.

If necessary, you can remake the connection – raise the locking flag and remove the conductor. Convenient, fast and reliable.

The 222 vago series can be used to connect two or three, even five conductors made of copper or aluminum (you can connect different metals in one terminal). Wires can be solid or stranded, but with rigid wires. Maximum section – 2,5 mm² . Soft stranded wires can be connected with a cross section from 0,08 mm² up to 4 mm².

One-piece

There is another type of clamps that does not provide for the possibility of redoing the connection of wires – the 773 and 273 series. When using these terminals, the work is generally seconds: the stripped wire is inserted into the appropriate socket. The spring present there clamps it, providing contact with the plate. All.

These spring-loaded wire clamps can be used to connect solid aluminum or copper wires with a cross-sectional area from 0,75 mm² up to 2,5 mm², stranded with rigid wires – from 1,5 mm² up to 2,5 mm². Soft stranded conductors cannot be connected using such connectors.

To improve contact, before connecting the wires, it is necessary to clean the oxide film. To prevent further oxidation, wago manufacturers also produce contact paste. It fills the inside of the clamp and it itself corrodes the oxide film, and then protects the wires from further oxidation. In this case, only highly oxidized, dark conductors need to be pre-stripped, and the clamp body is filled with paste.

By the way, manufacturers say that, if desired, the wire can be pulled out of the clamp. To do this, they take the wire with one hand, hold the terminal box with the other and rotate them back and forth with a small range, in opposite directions, stretching in different directions.

Clips for lamps (construction and installation terminals for lamps)

For quick and convenient connection of lamps or sconces, wago has special terminals of the 224 series. With their help, you can connect aluminum or copper wires of different sections and types (solid or stranded with rigid wires). Rated voltage of this connection is 400 V, rated current:

• for copper conductors – 24 A
• 16 A for aluminum.

Cross-section of connected conductors on the mounting side:

• copper 1,0 ÷ 2,5 mm2 – single-core;
• aluminum 2,5 mm2 – single-core.

Cross-section of connected conductors from the chandelier/sconce side: copper 0,5 ÷ 2,5 mm2 – single-core, stranded, tin-plated, crimped.

When connecting aluminum wires, the use of contact paste is mandatory, and copper wires must be manually stripped to bare metal.

This product has two drawbacks. First, the price of original terminals is high. The second – there are a lot of fakes at a lower price, but their quality is much lower and it is they who burn and melt. Therefore, despite the high cost, it is better to buy original products.

PPE caps

PPE caps (stands for “connecting insulating clips”) are very easy to use devices. This is a plastic case, inside of which there is a spring that has a conical shape. Conductors stripped of insulation are inserted into the cap, the cap is scrolled clockwise several times. You will feel that it has stopped scrolling, which means the connection is ready.

These conductor connectors are produced by many manufacturers, there are different sizes, for different diameters and the number of connected conductors. In order for the wire connection to be reliable, the size must be selected correctly, and for this it is necessary to understand the markings.

After the letters of the PPE comes a few numbers. Depending on the manufacturer, the number of digits varies, but they mean the same thing. For example, there is this type of marking: PPE-1 1,5-3,5 or PPE-2 4,5-12. In this case, the number immediately following the letters indicates the case type. “1” is set if the body is an ordinary cone, on the surface of which grooves can be applied – for a better grip. If there is a PPE-2, then there are small protrusions on the case, which are convenient to take with your fingers and twist.

All other figures reflect the total cross section of all conductors that can be connected using this particular PPE cap.

For example, PPE-1 2,0-4,0. This means that the body of the connecting cap is ordinary, cone-shaped. With it, you can connect two conductors with a cross section of at least 0,5 mm² (in total, they give 1 mm, which corresponds to the minimum requirements – see table). Maximum conductors included in this cap, the total cross section of which should not exceed 4 mm².

In the second marking option, after the PPE abbreviation, there is only a number from 1 to 5. In this case, you just need to remember which one is useful for which wire section. The data is in another table.

By the way, only copper wires can be connected with PPE caps – aluminum conductors, as a rule, are thicker than the maximum allowable for these connectors.

Bolted connection

This connection is assembled from a bolt of any diameter, a suitable nut and one, or better three, washers. It assembles quickly and easily, serves quite a long time and is reliable.

First, the conductors are stripped of insulation, if necessary, the upper oxidized layer is removed. Further, a loop is formed from the cleaned part, the inner diameter of which is equal to the diameter of the bolt. To make it easier, you can wrap the wire around the bolt and twist it (the middle option in the right picture). After all this is assembled in this order:

• A washer is put on the bolt.
• One of the conductors.
• Second puck.
• Another conductor.
• Third puck.
• Nut.

The connection is tightened first by hand, then with the help of keys (you can take pliers). That’s all, the connection is ready. It is used mainly if it is necessary to make a connection of wires from copper and aluminum, it can also be used when connecting conductors of different diameters.

How to connect aluminum and copper conductors

By the way, let us recall why it is impossible to directly connect copper and aluminum wires. There are two reasons:

• Such a connection is very hot, which in itself is very bad.
• Over time, contact weakens. This is because aluminum has a lower electrical conductivity than copper, and as a result, when the same currents are passed, it heats up more. When heated, it expands more, squeezing out the copper conductor – the connection gets worse, it heats up more and more.

To avoid such troubles, copper and aluminum conductors are connected using:

• terminal blocks;
• wago;
• bolted connection;
• branch clamps (make wire connections on the street).

Other types of connectors cannot be used.

How to connect wires of different diameters

If it is necessary to connect conductors having different diameters, twisting must not be present to obtain good contact. So you can use the following types:

• terminal blocks;
• wago;
• bolted connection.