When repairing (even cosmetic), we often encounter the need to tidy up the wiring. In old houses it happens that the wires are almost the same age as the owners of the apartment, and therefore it is simply necessary to replace entire sections of the wiring.
But this is the main problem: very often the old wires are made of aluminum, and for replacement you only have a piece of copper wire. Immediately make a reservation that by all rules it is strictly forbidden to dock them, but there are all kinds of situations.
So in this article we will discuss aluminum and copper wires. How to connect them, so as not to become the culprit of a short circuit and fire?
Why can't you do this?
So that you fully understand the danger of such actions, you should talk about why copper and aluminum wires should not be twisted. It is necessary to recall physics and chemistry.
Do you remember what a galvanic cell is? Roughly speaking, this can be called a battery, the current in which arises as a result of the interaction between two metals in an electrolyte. Accordingly, the twist between aluminum and copper is such a battery.
Of course, in dry air the formation of galvanic currents, which quickly destroy the material, is practically excluded. Yes, even a twist to the outlet, which is constantly used to connect a kettle or other powerful device, will not fall apart after a couple of hours, but troubles are waiting for you for sure.
Judge for yourself: over time, the materials of the wires are gradually destroyed, the resistance is constantly increasing. Accordingly, the place of twisting begins to heat up very much when a powerful current consumer is connected to the outlet. If this happens regularly, then the likelihood of a fire becomes extremely high.
That is why it is not recommended for a long time to connect aluminum and copper wires. How to connect them if there is an urgent need? Agree, in the country it is not always possible to visit the electric goods store!
Recommended Way
We repeat once again that it is far from always possible to do everything “according to science,” but we still strongly recommend using terminal blocks to connect the wires. This is the easiest, fastest and safest way by which even the most inexperienced electrician can connect the wires. Consider the most common constructive types.
"Nuts"
The oldest and most proven way are terminal blocks for connecting wires, called nuts. As you can understand, they got the nickname because of their specific form. Structurally, they consist of three plates, between which the wires are fixed.
A particular advantage of this method is the fact that it is not necessary to cut the central line to insert the second wire. To do this, you just need to peel off the insulation in the right place, and then clamp this section between the two “walnut” plates. An outlet wire is inserted between them, after which the plates are reliably twisted together.
Wago
No less common are the methods of connecting wires, which are combined under the same acronym WAGO. These are very simple and reliable devices with which you can dock everything in a couple of seconds. This is done as simple as possible: the ends of the wires are stripped of insulation, after which they are inserted into the connectors.
The trick here is that the inner space of this compound is filled with a special lubricant, which prevents oxidation and galvanic reaction between different types of metals. But! We could recommend the use of such devices only in those networks to which powerful devices will not connect.
The fact is that under heavy load, connections of this type will become very hot, as a result of which the terminal materials will begin to break down. Not surprisingly, WAGO is most often used when working with lighting fixtures.
Terminal blocks
They are also quite common and popular. It looks most like a small bar with terminals. As in the case described above, for their use it is necessary to strip one end of the wire, then insert it into the adapter hole and tighten the bolts. On the other hand, everything is done exactly the same.
Here again, there is a snag. How will aluminum and copper wires behave in this case? How to connect them if you need to connect really powerful devices to the network?
Fortunately, pads are quite suitable for this purpose. If the thickness of the insulating plate is normal, then it can withstand even very high loads without problems. But remember that terminal blocks are not recommended for installation in a room with high humidity. There is no insulating lubricant in them, so the formation of a galvanic pair is not excluded.
What other methods of connecting wires exist? Let's figure it out.
Bolt fasteners
This installation method is also great when you need to join copper and aluminum. The wires are clamped with a bolt, and between the two metals it is necessary to put a washer made of high-quality anodized steel. Remember that this type of joint must be tested for strength at least twice a year. If such a joint is used in a network with high loads, then this should be done more often!
Soldering iron
Is it possible to solder wires that are made of different metals? Yes, it is quite possible, but some important conditions will need to be observed.
We will not talk about copper for a long time, since there should not be any difficulties in this matter. But with aluminum there will be problems. Their cause is amalgam, which instantly forms on the surface of this metal when it enters the oxygen medium. It is surprisingly resistant in chemical terms, and therefore the solder does not stick to it in principle. This is constantly faced by those novice electricians for whom any soldering of aluminum wires is a curiosity.
How to remove this annoying film? First you will have to prepare a saturated solution of copper sulfate, a Krona battery and a piece of normal copper wire (not Chinese). On an aluminum wire, it is necessary to carefully clean the place of future soldering, and then drop a couple of drops of copper sulfate solution on it.
Attach aluminum to the negative side of the battery, and a piece of copper wire to the positive side. Dip its end in copper sulfate. After a while, a fairly decent layer of copper will settle on the aluminum onto which you can easily solder the wire you need.
As you can see, the soldering of wires even in this case is able to provide a reliable and high-quality connection.
Important!
In almost all cases that we examined above, rigid fixation of wires stripped from insulation is used. Somewhere, terminals are used for this, somewhere bolts ... But few people take into account one important moment, twisting aluminum and copper wires. We already know how to connect them, but it is also worth talking about the safety precautions of this process.
The fact is that aluminum under load becomes quite plastic, it starts to “leak”. All (!) Connections of this kind need to be regularly checked and bolts tightened. Otherwise, the day will come when an honestly held terminal will simply flare up, unable to withstand strong heating.
Other tips
- Stranded copper wires must never be clamped. The fact is that when clamping, a whole range of conditions is formed that this wire does not like very much. So, part of the veins may well come out of the connection. The remaining part of the wire will have a very high load, which may result in a fire.
- It is very important to select the terminal exactly for the cross section of the wire you are using. A wire will simply drop out of a too narrow or wide channel, and this is fraught with unpleasant consequences.
- Do not pinch! In most cases, brass is used in the terminals and sleeves, and this material is characterized by increased fragility.
- Look carefully at the markings, which indicate the maximum permissible amperage. As a rule, it is exaggerated: it is better to divide the indicated value into two.
We do not recommend buying the so-called NoName from China. You will not go broke spending a couple more rubles, but buy a really high-quality terminal from a normal manufacturer! Manufacturers Tridonik, ABB, Believe have proven themselves excellently.
And what about the multi-core option?
If you carefully read the article, then you already know perfectly well that stranded wires should not be clamped. But what about when you need to connect them to a thick aluminum outlet, and you don’t have a soldering iron, copper sulfate and battery, and you don’t want to mess with them?
It is time to tell you that there are special types of wire connections that are designed specifically to solve these kinds of problems.
Sleeve connections
In specialized stores for electricians, you will most likely find sleeves specially designed for normal connection without too much difficulty. In appearance they look like miniature tournament spears of knights: a hollow metal tip follows a protective plastic cap.
How to work with them? Everything is simple: carefully remove the insulation from the end of the wire, twist the veins into one “pigtail”, and then insert it into the hollow tip. After that, the sleeve is crimped (you can use the most ordinary pliers). The resulting tip is pushed into the terminal.
So you can easily connect the wires without soldering. Of course, under the condition of the presence of a soldering iron, the aforementioned “pigtail” does not forbid anyone to irradiate solder and weld with aluminum in the way that we described above.
Twisting
Of course, twisting in the midst of professional electricians is considered a bad manners and almost a violation of professional ethics, but everything happens in life, and therefore no one is immune from the need to make such a connection.
What advice can be given in this case? To begin with, twisting of aluminum and copper wires is allowed only after a thorough stripping of the aluminum section. If the copper wire is presented in a multicore version, it must be sure to not only be twisted into one “pigtail”, but also covered with solder for better contact.
Twisting should be done as carefully as possible, avoiding breaking wires. It is recommended to close its ends with a special insulating cap, which can be bought in almost every hardware store.
Finally, we have repeatedly written that twisting should in no case be in a room with high humidity. Under such conditions, the compound is destroyed almost instantly.
In a word, it is not recommended that professional electricians make the connection of copper and aluminum wires, but using the simplest means, you can quite perform it without exposing your house to fire.