Any home electrical network must be protected - anyone who even at least casually touched on this topic knows about it. But not everyone knows what equipment is best purchased for these purposes. After all, each element of the system must be calculated according to certain parameters. In addition, many do not know how many poles are required for various protection. Today's article will tell you about how to choose an opening circuit breaker, separate the wiring into groups, which ABs need to be installed on a particular line and how these devices differ from each other.
General concepts of introductory automaton
Protection of any electrical network begins even before the meter. The opening circuit breaker, which is the main unit of the entire system , is the first to be installed on the line. Even if the remaining ABs fail in the switchboard, with a short circuit, this device will have time to react before the wiring insulation ignites. The speed of a correctly selected input automaton is enough even to protect the electricity meter standing in the circuit after it.
For conventional networks with a voltage of 220 V, two-pole input circuit breakers are used - circuit breakers with four contacts. According to the rules of the electrical installation (PUE), the input cable must be broken both in zero and in phase. That is why machines on the 1st pole are not applicable here.
The difference between the switch and the opening machine
The most frequently asked question by beginners in this area is: is it possible to install only an automatic machine on the input, without an additional knife switch or batch switch? At first glance, it seems that such actions do not contradict the PUE, but the problem here is not that such installation is prohibited. The point is the design features of the equipment.
The circuit breaker or batch switch does not have complex elements in its circuit, they are simple and therefore reliable. For such circuit breakers there is no certain number of cycles that they can withstand. Therefore, if you plan to frequently disconnect the network, then in front of the opening circuit breaker should put a bag or switch.
Why you should not often use AB
The problem with high-tech machines is that they have a certain resource in cycles. Usually it is equal to 8000-10 000 inclusions. This means that after that the device will either completely stop working, or simply will not remove the voltage from the network if an overload or short circuit occurs. But it is not a fact that the device will withstand the number of cycles promised by the manufacturer. From this it follows that it is not worth using an introductory circuit breaker often. It is better to install a knife switch or bag for these purposes.
The cost of machines is not too high, but no one wants to overpay too much, which means that the most correct will be the scheme in which the location of the elements will be as follows (from the feed):
- Circuit breaker or batch switch.
- Introductory machine.
- Electricity metering device.
- Wiring on UZO, AVDT, etc.
If necessary, the production of periodic audits (1-2 times a year), you can use the introductory circuit breaker. If breakdowns occur frequently, it is better to relieve tension from the switch or bag.
Protective automation for networks with a voltage of 380 V
Many people believe that three-phase systems are complex and inconvenient to install. However, such an opinion is erroneous. On the contrary, if you look, then such networks can be called the most simple to install and maintain. Here, a four- or three-pole input circuit breaker is installed in front of the metering device. And it is precisely about the number of contacts that disputes between experts constantly go on. Some argue that a zero break is necessary, just like with a two-wire system, while others, on the contrary, say that the fourth contact is an additional weak link in the circuit.
Logically, it is better to use a four-terminal device as an input automaton, however, practice shows that not everything is so simple. It is the zero contact of such a device that most often fails. What is the reason for this problem? Experienced electricians know that the main load falls on the zero terminal - with a weak contact the first one starts to burn. At the same time, there is no such problem in the 2-pole machine. It’s worth a try.
Why does the 380V input circuit breaker fail?
Most often, the main problem of burning off or sticking to the zero contact lies in the laziness or carelessness of the electrician who collects, and then maintains the circuit. With a two-wire system, the neutral load is not too high. That is why the machine will work much longer. But at 380 V, 3 phases immediately exert a load on the zero contact, which with poorly stretched terminals becomes fatal for protective equipment.
To "treat" a similar "sore", you should check all the zero contacts. The most convenient way to revise the distribution panel is to examine it with a thermal imager, on the screen of which problem areas where the temperature is higher are instantly visible. However, units have such expensive equipment, which means that you will have to go through all the connections and properly stretch them. Particular attention should be paid to the zero bus.
If the audit is done, and after a short time the cutter again fails, it remains to use the most rational option - to install a 3P (three-pole) automatic input switch. However, this is only allowed if there is a protective shutdown device in the circuit that can protect people living in the apartment or house from electric shock. Instead of an RCD, you can use a residual current circuit breaker (AEDT).
For those who want to learn more about installing an introductory machine, below is a video that will explain a lot.
Rated current load of circuit breakers
This parameter is selected based on the total power consumed by all household appliances. If we talk about an ordinary apartment, then rarely this figure exceeds 5.5 kW. With such a load, the best option would be to use an input 25A circuit breaker. However, this statement is true only for 220 V. networks. If the input is carried out through a four-wire system, then the maximum load indicator for such a machine will be 9.5 kW.
It is allowed to use devices with a rated current load of 25 A and for linear automatic machines for powering equipment up to 5.5 kW, however, the input cut-off must have higher values.
What to look for when buying protective equipment
When choosing an opening circuit breaker, it is important not only to correctly calculate its characteristics. It is necessary to be extremely careful when buying, so as not to purchase counterfeit products. The first step is a visual inspection. The case of the machine must have a uniform color, without extraneous inclusions. Irregularities of the casting should alert the buyer, as well as large gaps in the area of the “flag”. But the main secret is hidden on one of the side panels.
The main task of counterfeiters is to earn as much money as possible. Therefore, they do not bother to install real automation inside the cutter. And here's how to find out. This original device has a thick rubber stopper on the side panel. If you pull it out, a bimetallic plate is found under it, which is responsible for cutting off and releasing voltage from the circuit during overheating. So, on falsified products, the indicated cork will simply be drawn - it will not be possible to open it.
If you disassemble such a product (you cannot call it an automatic machine), only the contact group will be found inside without any additional elements like a solenoid, rod or plate. In fact, this is a normal switch, not able to protect anyone and anything.
Where is better to buy protective automation
Many users claim that purchases through the Internet are the most profitable, but this clearly does not apply to the equipment being disassembled today. Indeed, in this case it is impossible to see the product with your own eyes. It turns out that a person buys a cat in a poke. But after all, not only the health safety of those living in an apartment or a house, but sometimes people's lives also depends on the originality of the purchased machine. That is why experts advise buying such equipment only in specialized, trusted stores with a good reputation.
The prices of introductory circuit breakers are low (from 200 to 1000 rubles), so you should not try to find even cheaper goods through the Internet - it will most likely turn out to be a low-quality counterfeit.
Finally
The choice of an introductory automaton is not as complicated as it might seem at first glance. The main thing is to approach him carefully and carefully. It should be remembered that this is the last stage of protection. And if it happens that the rest of the automation fails, we will only have to hope for an introductory cut-out. So, the home master must be one hundred percent sure of it.