Correct connection of electrical wires: crimping or soldering

Recommendation points

• Soldering wires: where appropriate
• Links and sleeves
• Cable line connections
• Spring and screw terminals
• Connection isolation methods

The question of the best type of household electrical connections has always been ambiguous. Perhaps, in addition to the usual terminal blocks and soldering, something new has been invented? Let’s figure it out, and at the same time find out how a set of specific object conditions affects the choice of the connection method.

Soldering wires: where appropriate

Lead-tin solder joints provide sufficient electromechanical strength, but have a number of very significant drawbacks. Even with stand soldering in a well-equipped place, a defect is possible, and in cramped conditions of desoldering boxes under the ceiling, it is almost guaranteed. The situation is aggravated by the inability to completely remove the residual flux, which over time causes the gradual destruction of the adhesion site.

Poor soldering of wires will certainly result in a problem in the future.

It makes no sense to solder stranded conductors at all: it is almost impossible to pre-twist tightly, which is why tin does not displace all the air. The porous compound gets very hot, corrosion intensifies over time, and the contact disappears due to the oxide layer. Similar phenomena are observed in spikes walled up without localization by boxes, which, strictly speaking, is in principle unacceptable in modern installation, regardless of the connection method.

Departure from this rule causes an avalanche formation of oxides in conditions of high humidity. They underestimate the conductivity between copper conductors, but at the same time make the wall partially conductive due to salts dissolved in water – hence electric shocks and short circuits.

Here’s what happens if you do not follow the rules for soldering the power cable

Nevertheless, soldering is a fairly fast and least expensive method of connection with a fairly long service life. It is recommended to solder connections in serviced cabinets and boxes, to tin stranded conductors for screw terminals, to connect cables by soldering while protecting them with waterproofing sleeves. Soldering also serves as a good protection against oxidation in dry air, therefore other types of connections are strengthened with it: sleeve-crimp and screw.

An example of correct soldering of a power cable

Remember, however, that the main disadvantage of soldering in such cases is the inseparability of the connection, so it is not suitable for potentially temporary contacts. It would also be a mistake to solder by weight without providing preliminary mechanical fastening of the conductors to be connected by twisting or otherwise. The slightest movement in the cooling solder layer causes its overall porosity, which leads to the consequences described above..

Links and sleeves

In electrical installations of any kind, a bare “twist” serves as a temporary connection of conductors during testing and debugging. Such a connection cannot work in a constant mode due to the mechanical action of the current and the elastic properties of the copper alloy. There is another reason: to maintain the nominal conductivity at the junction, the twisting must be very long, because the contact area of ​​two round wires is minimal.

Options for twisting or joining wires. Mechanical connection of wires – temporary solution

All these disadvantages are eliminated by crimping the twists or individual cores using sleeves. At the same time, the conductors are deformed and adjoin each other with a significant contact area, and the density of their pressing is provided by an external belt that is not subject to the action of current.

In practice, it makes sense to connect by crimping conductors with a cross section of 10 mm² and more, with less thick wires, it is more difficult to control the crimp quality. As a tool for working with cables up to 35 mm² it is better to choose manual lever crimpers, arranged in the manner of bolt cutters: they are mobile, moreover, on small sections, one muscle strength is enough.

Sleeve crimping improves wire contact and mechanical strength of the connection

Large live lines (from 50 mm²), in addition to their massiveness, complicate the work with a high degree of responsibility. High-quality crimping is possible only with a hydraulic tool, of which there are two types. Lever jacks combined with a matrix in one body are perfect for working on cable lines. It is especially convenient to work with such a tool at a height..

When assembling panels and in cramped conditions, it is better to prefer separate pressure operators, in which the oil pump is made with a pedal drive and is connected to the working part with a high pressure hose.

It is extremely important to remember that reliable compression is only possible with static force. Therefore, pressing the tips and sleeves with a hammer (chisel) is strictly prohibited..

Cable line connections

The standard for the quality and reliability of cable connections is the majority of cable couplings used for joining sections of trunk power lines. We mentioned above that you cannot brick connections into a wall, but in some situations this cannot be avoided. For example, with a long line length or using an expensive thick cable.

The clutch design demonstrates how the connection should be made under such conditions. The veins in them are crimped with sleeve lugs with a controlled tightening torque. It can be both sleeve-screw and crimped connections, but they are invariably protected by a layer of solder.

The link (twisting of two stranded wires with alternating overlap of the cores) of each core is insulated separately by two layers of insulation: thermal and waterproof, and the bundle itself is divided by a rigid liner and surrounded by external waterproofing, the edges of which are tightly adhered (glued) to the outer sheath of the cable. All these principles should be implemented in every maintenance-free connection, when operating in conditions of high humidity, aggressive environments and on flammable substrates..

Spring and screw terminals

The above is easy enough to practice in everyday work with household networks. Since the rejection of stranded conductors has become almost commonplace, you can connect either monolithic conductors or strands processed by soldering or sleeve lugs. One of the oldest and most reliable methods is with screw blocks, which cut deeply into the core and provide good contact at the expense of the dynamic strength of the core. For permanent connections, it is also recommended to fill with hot melt glue the open parts of the pads and “necks” of screws.

Alternative to such connections are WAGO spring clamps and the like. The vein in such a clamp can be bent several dozen times, and it will not break off in a weak spot. For use in humid environments, it is recommended to purchase spring pads filled with petroleum jelly. Such devices, despite a slight increase in the total cost of the project, remain detachable to quickly change the network configuration when an error is detected, at the same time, their service life is comparable to the cable – from 50 years.

Wago quick coupler

Connection isolation methods

The principles of absolute localization of the cable joint are embodied in household power grids by junction boxes. A wide range of degrees of dust and moisture protection (IP) allows you to choose a product that is justified in cost and suitable for specific conditions. Absolutely all connections, except for cable sleeves, should be equipped only in such boxes, which, by the way, may not be serviceable.

Wire insulation is not required when connecting with screw and spring terminals. Sleeves and end pieces are insulated with 1-2 layers of heat-shrinkable tubing. To prevent the material from vomiting during heating, the crimping irregularities must be removed with a file, or wrapped with 2-3 layers of Mylar tape. Similar pipes should be used to repair damage to the core insulation and protect the edges of the cores, stripped with unnecessarily long.

The wires inside the box and their connections should not, if possible, block access to each other

When mounted inside the box, the cores must also be split. Usually, phase conductors are first separated at the bottom of the box, separated by distance clips, or fixed to the body. A plastic gasket cut from a regular PET bottle is laid on top of the wiring, then zero and protective conductors are laid on top.