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What is the danger of old wiring
When we hear the phrase “old wiring”, a very specific image pops up in our memory: two thin aluminum wires in common single-layer insulation with a wide and flat separation gap. Since the insulation is common, the phase and zero conductors, of course, do not differ in color in any way. What brand did that ever-memorable cable have? And it’s hard to remember, although it is still on sale to this day. Of course, we do not recommend using it.
Today, it can rightfully be said that aluminum in household wiring has already outlived its own. This is confirmed by the rules of the PUE, prohibiting the installation of aluminum conductors with a cross section of less than 16 square meters. mm But even without these norms, it has long been known that aluminum wires always form a film of non-conductive oxide on their surface, which often becomes cause overheating of contacts. In addition, the mechanical properties of aluminum, being not up to par and without it, from overheating become even worse: the conductor becomes brittle, can break off at any time.
In order to somehow minimize the disadvantages of aluminum wiring, quartz-petrolatum grease is used at the junction points of the conductors, and it is recommended that the connections themselves be inspected and revised periodically during operation. But who does all this in an ordinary apartment, the owners of which are not particularly knowledgeable in electrical engineering?
This question can be considered rhetorical. So it turns out that many apartment owners in old houses are forced to put up with sparking from outlets, switches, junction boxes, until change the wiring to copper.
By the way, a few words can be said separately about the junction boxes. In homes with old wiring, these boxes often become a source of trouble. Partly - for the reasons mentioned above, and partly - simply because any special clamps for connecting wires in the old days were not used.
Often the wires were simply twisted with pliers and wrapped with electrical tape. After decades, in the absence of the ability to replace the wiring, it is necessary to at least systematically inspect the twists in the boxes for signs of overheating. But after several “waves” of cosmetic and major repairs, after a repeated change of owners and, possibly, even a change in layout, who can tell where these boxes are? Where can we find them under a thick layer of plaster? And are there such tricky places where the twists are located outside of any boxes, for example, in the grooves between the floors?
But poor twisting can lead not only to a short circuit and wiring failure, but also elementary may cause fire.
A similar pattern is observed in old switchboards. Bad contacts, arcing, burned-out aluminum conductors with blackened insulation ... Let us add to this “company” old-style circuit breakers with broken-off handles, the operation threshold of which is already unknown to anyone (if they can work at all, since their contacts could have been attached to each other for a long time) )
Do not forget to mention the “elegant” introductory bag, for turning the handle which may not be enough effort with one hand. The most interesting thing is that the contacts of this bag over the years could have lost their elasticity, and this often leads to internal overheating. All of the above is a direct possibility of a fire.
Another danger associated with the operation of any old, and not just aluminum wiring is the risk of leakage currents. Their appearance is associated with aging of the insulation of conductors, that is, with the fact that it loses its insulating properties.In general, the wear of any conductors is determined, first of all, by the wear of the insulation.
So, insulation wear leads to leakage currents, and protection from the latter is simply not provided for in the old wiring systems. As a result, the electric potential of the network can be on any conductive surface in the house: on pipes of water supply and sewage, on the surface of the sink and ventilation duct, and the like.
Of course, it will not always be full-fledged 220 volts, but an electric shock will be quite noticeable. And you should not hope that third-party conductive parts in your house are grounded, because the state of this grounding is not controlled by anyone, even after the replacement and repair of utilities.
It turns out that in fact potential equalization systems in old houses, they are missing or not working, and thanks to the worn-out insulation of the wires, you can get an electric shock at almost any time. And large leakage currents can even cause heating in the place of poor contact and, as a result, a fire. It is for this reason that installation is recommended at the entrance to the living room by current regulations differential protection apparatus with a nominal value of 100 or more milliamps.
Finally, we note that the dangers arising from the old wiring - the danger of fire and electric shock - are compounded by the fact that the third, protective neutral conductor PE in TN-C system not installed. "Add" it is simply impossible now, sometimes even with a complete replacement of the wiring.
This means that owners of apartments with old wiring made with a two-wire aluminum cable, with some exaggeration, “walk along the edge of a knife”, balancing between the prospect of fire and electric shock. Indeed, most likely, the lack of protective grounding will detect the problem when the trouble already happens.
Read also on this topic: Diagnostics of the electrical wiring of the apartment before buying
See also at bgv.electricianexp.com
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