Connecting electrical wires: not just twisting 

Tell me, what is the first thing that comes to mind when hearing these words? For many, it’s a banal twist, electrical tape, and off you go. And then they wonder why the object is heating up, sparking, or worse. In fact,connection of electrical wires- this is a whole layer of standards, technologies and, more importantly, practical experience, which often contradicts the “old-fashioned” ones. methods. I myself saw how at a construction site they were trying to use aluminum and copper in a “cunning” way. connect with a sleeve without proper crimping - after six months the section of the route will be replaced under warranty, and it’s good if there are no consequences.

Basic principles that are often ignored

Let's start with something simple: any connection must be electrically and mechanically reliable. These are not empty words. Electrical contact is the contact area, compression force, and the absence of oxides. The twist, even tight, weakens over time due to temperature deformations. Especially in power circuits. Hence the requirements of the PUE, which directly indicate welding, soldering, crimping or the use of certified clamps.

One of the key points that beginners miss is the preparation of the guide. Stripping the insulation. If you damage the core with a knife, a point of increased resistance and local overheating will appear in this place. For multi-wire conductors, it’s a completely different story. They must be twisted correctly before being inserted into a sleeve or terminal, otherwise individual wires will be knocked out and contact will deteriorate. There was a case where at one of the facilities, due to the fault of a subcontractor, the ventilation control cabinet burned out because of this. The reason is incomplete contact in the screw terminal on the starter due to “fluffy” stranded wire.

And more about materials. Copper and aluminum. It would seem that everyone already knows about galvanic couple and oxides. But there are still “craftsmen” who use ordinary terminal blocks, not bimetallic ones, to connect them. Or, worse, they lubricate the twist with Vaseline, thinking that this will protect it. Vaseline is a dielectric, it worsens contact! We need special inhibitor pastes, for example, “Kontaktol?” or analogs that displace oxygen and prevent oxidation. But it’s better to avoid such connections altogether and use transitional bimetallic sleeves or tires.

Connection methods: from welding to modern clamps

If we talk about massive, reliable connections in junction boxes, welding is still considered one of the best methods for copper. Not soldering, but welding. Soldering has a right to life, but with vibrations or high currents, the solder can “float”. Welding creates a monolith. But here you need the right equipment, a carbon electrode, skill - it’s also easy to burn out the core. I saw how the guys fromShijiazhuang Hist Electric Co.,LtdAt one of the complex facilities, we were welding twists in a floor panel - the work was clean, neat, all connections were after heat shrinking. Their profile states that they work in difficult conditions, and these are not just words - they need exactly this kind of precision.

Sleeve crimping is my personal favorite for power lines. GML sleeve, HEXAGONAL press (hexagonal), not round! Round crimp is for low current only. The hexagon compresses evenly over the entire area, with minimal contact resistance. It is important to choose the correct sleeve size - not only by cross-section, but also by the total cross-section of all cores, if there are several of them. And be sure to check the completeness of the compression - cut off one control sample, cut the sleeve lengthwise and see if there are any voids. I did this myself when I was training a brigade.

Screw and spring terminals (Wago, IEK, ABB). There's a lot of controversy here. Modern spring terminal blocks with paste are an excellent solution for lighting and low-current circuits, for mounting lighting devices. But for power circuits with currents above 16A and, most importantly, with starting currents (motors), I would be careful. Screw ones are more reliable, but require regular tightening, especially on aluminum. And you cannot clamp two dissimilar metals into one terminal without an adapter plate. On their websitehiste-ru.comin the technical support section there are recommendations for selecting accessories for different types of cable, which indirectly confirms the importance of making the right choice specifically for specific installation conditions.

Problems in practice: moisture, vibration, temperature changes

Everything works perfectly in a dry, warm junction box. Now imagine a basement, garage, street, or workshop with vibration. This is where theory meets reality. Tightness becomes critical. Heat shrink with an adhesive layer is a must have. But it also needs to be heated correctly, evenly, so that the glue spreads over the entire surface. Passages through walls must be in a sleeve, with an omental seal.

Vibration is the killer of screw joints. Even with Grover's washers they can come off. There is either a double nut with a lock nut, or a spring washer plus proper preparation of the end of the wire (a ring or fork to match the size of the terminal). Or better yet, pressed tips NSHVI, which will no longer fluff up? under the screw. At one of the production facilities, it was necessary to redo all the connections to the machines precisely because of vibration - they replaced the bare wires with crimped tips, the problem went away.

Temperature changes. Aluminum especially “walks”. A connection made in the summer may weaken by winter. That’s why regular revision and stretching is so important. For critical connections, sometimes they even install special indicator washers that show the degree of clamping weakening. This is already a high level, but for important objects that he writes about in his companyShijiazhuang Hist Electric Co.,Ltd, providing comprehensive solutions, such subtleties are precisely what distinguishes high-quality installation.

Monitoring and diagnostics: nothing without it

Made a connection - check it. The easiest way is not only to “pull” per wire, but also measure the contact resistance with a microohmmeter. Yes, not everyone has it. But on large objects this is mandatory. The spread in resistance of similar connections should not exceed 20-30%. You can also use a thermal imager after applying the load - the most obvious method. The heating connection is immediately visible. After the commissioning of the facility, we always had thermographic photography of the boards under load.

Another point is labeling. It would seem nonsense. But when there are 20 wires in a box, and all are black, and after a year you need to find the phase from a specific switch... Spend five minutes marking with sleeves or at least tags - you will save a day later. This is a discipline that comes with experience, after several rush jobs with troubleshooting.

And of course, an act for hidden work. If the connection is sewn into a wall, into a screed, photographic fixation is required before closing. This is not bureaucracy, it is insurance against claims and a guarantee that everything is done wisely. After all, opening it later is a huge expense. An integrated approach, including documentation, is what distinguishes just installers from the engineering and technical support that serious contractors declare.

Instead of a conclusion: thinking out loud

So, back to the beginning.Connecting electrical wires- this is not a stage that can be done anyhow. This is the foundation of the entire system. If you save time here, you will spend ten times more on finding and eliminating consequences. Technologies and materials do not stand still, new solutions are emerging, the same self-clamping terminals for large cross-sections. You need to monitor, try in uncritical areas, but also not abandon proven methods where they are critical.

It is the ability to choose the right method based on the conditions, and not just do it “according to a template?” - this is the sign of a competent specialist. As, in fact, the ability to admit that here, at this node, I once made a mistake, because I wasted time on a full-fledged crimping. Experience, after all, consists of such practical lessons, and not just from read instructions.