The connection of current-carrying cores is a responsible event. Indeed, with careless or incorrect operation, the contact will be unreliable, and the wiring in this place will begin to warm up. During heating, the metal is deformed, which can break the contact. Such a situation, at best, will lead to the failure of electrical wiring and equipment. At worst, a fire is possible.
Photo: joserpizarro/Fotolia.com. When choosing one or another connection method, it should be remembered that repairs may have to be carried out in adverse conditions (lack of space, inconvenient location of the connection area, etc.). In this situation, modern means of switching (terminals, caps), as a rule, are much more convenient than soldering, and even more so welding.
How should an electrician act? The «Electrical Installation Rules» state: «… Connection, branching and termination of wire and cable cores must be carried out by crimping, welding, soldering or clamping in accordance with the current instructions approved in the prescribed manner.» This list does not include “twisting”, the most popular connection method in everyday life. It is believed that this method is not reliable enough. Today, it is not recommended to use “clean twist” — it must be reinforced by soldering, welding, crimping sleeve or PPE connecting cap. Each method has certain merits.
Photo: Boris Bezel/Burda Media. Devices for switching wires: blocks with screw terminals
Perhaps the most reliable options. But only a specialist using the appropriate equipment can perform high-quality soldering, and even more so welding. Therefore, it is best to leave these methods to professional installers.
Photo: Boris Bezel/Burda Media. PPE connection caps screwed onto twisted conductors
Crimping with a sleeve
In this case, you will also need a special tool — press tongs. Inexpensive models will cost 1-2 thousand rubles. Learning how to properly handle them is much easier than, say, with a welding machine. At the same time, crimping ensures a high-quality connection. It is only important to carefully twist the cores and select a sleeve of a suitable diameter so that it fits snugly against the wires and does not hang on them. Crimping is optimal for connecting multicore cables.
Connecting caps PPE
They are put on twisted cores and screwed onto them with little effort (there is a thread inside the products). PPE caps are widely used, since no additional tools are needed to install them. They differ in the diameter of the bundle of cores for which they are designed. The PPE cap should be chosen very carefully, otherwise it will not hold well.
When using them, each core is inserted into a separate groove. This option, in particular, allows you to switch aluminum and copper conductors, which should not be in direct contact with each other. There are many types of pads, the simplest are screw ones, where the core is held by a tightened screw. The disadvantage of screw connections is that they need to be tightened regularly (say, once a year) to compensate for the fluidity of the conductor metal. Therefore, spring terminals are considered more advanced, in which the spring connection technology does not allow the contact to weaken. Spring terminals are designed and manufactured by WAGO. Connections of this type do not require maintenance, since the materials and design of the terminal provide high-quality contact between the latter and the conductors for many years.
Comparative characteristics of aluminum and copper wires
- Aluminum wire allows a lower current load with the same wire cross section.
- Aluminum wire is less ductile and breaks more easily.
- Aluminum oxidizes in air, and over time, the oxide film worsens the contact of the wires. To prevent oxidation, air access to the metal should be excluded. For this purpose, special heat-shrinkable tubes are used that are put on the connected wires, or a special electrically conductive paste is applied to the connection.
- Metals have the ability to gradually deform under load (yield), so screw connections weaken over time. In aluminum, this unpleasant property is much more pronounced.
Source: Ideas for Your Home Magazine#201