Problem of connection of copper and aluminum wires
Often "house electricians", repairing the power supply network, dotachivat the aluminum wires which became useless and demanding partial replacement, copper. Similar actions are inadmissible. Why do not recommend to connect copper and aluminum wires directly?
Generally it is connected with high oxidability of aluminum. Over time on the surface of aluminum there is the oxide film which has very high resistance, and it strongly reduces the tokoprovodimost of such connection. And here copper wires are less subject to oxidation, and the oxide film on them has small resistance , therefore, it affects the tokoprovodimost very slightly.
After compound of copper and aluminum electric current passes through oxide films of these metals that can significantly complicate the tokoprovodimost in this junction as these conductors have different electrochemical properties.
The matter is that electric current acts as the catalyst of this reaction, and the more value of current, the quicker oxidation happens. As a result the bulb/socket can suddenly spontaneously cease to work or the place of contact will strongly heat up. The electrical link is broken at the expense of thermal expansion, and when cooling the problem place the contact appears again.
Professional electricians if necessary "to combine" aluminum with copper in the power supply network use "intermediary" - the steel anodized bolt, the nut and washers that between the copper and aluminum wire there was the steel washer, and the "clashing" metals did not contact at all. It is also possible to use the washer from galvanized iron.
It is necessary to remember that the wire which is broken off in the middle of the wall cannot be twisted and "immured" in plaster for several reasons:
- isolation of the wire is broken that can lead to "punching" of the phase on the wall;
- the integrity of the wire is broken - the probability of heating of the place of contact and insulation failure at the heavy load is high;
- at the "wrong" twist there is no opportunity to correct the error.
At detection of the rupture of the wire in the middle of the wall it is necessary to replace completely the wire, from the contact box to the socket/bulb/switch. It is admissible in the place of the gap to place the terminal box, it is desirable having deepened it under the plaster coat. It is "not as esthetic" as full replacement of the wire, but often is the simplest decision. There is one more method. We take also obluzhivay the copper wire tin by means of the soldering iron, and then we do ordinary twist. It is also possible to use modern clips or transitional blocks.
In conclusion it is possible to sum up the result: to protect itself from future problems, to twist copper wires with aluminum is not necessary better.Top