Any home electrical network must be protected - everyone who even casually touched on this topic knows this. But not everyone knows what equipment is better to buy 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 how to choose an introductory circuit breaker, divide the wiring into groups, which ABs need to be installed on a particular line, and how such devices differ from one another.
General concepts of the introductory machine
Protection of any electrical network begins even before the meter. The very first on the line is an introductory circuit breaker, which ismain node of the whole system. Even if the other ABs in the switchboard fail, in the event of a short circuit, this device will have time to react before the wiring insulation ignites. The speed of a properly selected introductory machine is enough even to protect the electricity metering device standing after it in the circuit.
For conventional networks with a voltage of 220 V, two-pole input automata are used - automatic switches with four contacts. According to the rules for the installation of electrical installations (PUE), the input cable must be broken both in zero and in phase. That is why 1-pole automata are not applicable here.
The difference between a knife switch and an introductory machine
The most frequently asked question by beginners in this field: 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.
A knife switch or a batch switch does not have complex elements in its circuit, they are simple and therefore reliable. For such breakers, there is no set number of cycles that they can withstand. Therefore, if you plan to often turn off the network, then you should put a bag or a knife switch in front of the introductory circuit breaker.
Why you shouldn't use AB often
The problem with high-tech machines is that they have a certain resource in cycles. Usuallyit is equal to 8000-10,000 inclusions. This means that after that the device either completely stops working, or simply does not remove voltage from the network in the event of an overload or short circuit. But it is not yet a fact that the device will withstand the number of cycles promised by the manufacturer. It follows from this that it is often not worth using the introductory circuit breaker. It is better to install a switch or a bag for these purposes.
The cost of the machines is not too high, but no one wants to overpay, which means that the most correct scheme will be in which the arrangement of the elements will be as follows (from the feed):
- Knife switch or package switch.
- Introductory machine.
- Electricity meter.
- Wiring for RCDs, RCBOs, etc.
If it is necessary to produce periodic revisions (1-2 times a year), you can use the introductory circuit breaker. If breakdowns occur frequently, then it is better to remove the voltage from the switch or bag.
Protective automation for 380 V networks
Many believe that three-phase systems are difficult and inconvenient to install. However, such an opinion is erroneous. On the contrary, if you look, then such networks can be called the easiest to install and maintain. Here, a four- or three-pole introductory circuit breaker is installed in front of the electricity meter. And it is precisely about the number of contacts that there are constant disputes between specialists. Some argue that a zero break is necessary, just aswith a two-wire system, while others, on the contrary, say that the fourth contact is an additional weak link in the chain.
If you think logically, it is better to use a four-terminal circuit as an introductory automaton, but practice shows that not everything is so simple. It is the zero contact of such a device that fails most often. What is the reason for such a problem? Experienced electricians know that the main load falls on the zero terminal - with a weak contact, it is she who starts to burn first. At the same time, there is no such problem in the machine for 2 poles. Worth trying to figure it out.
Why does the input circuit breaker 380V fail
Most often, the main problem of burning out or sticking of the zero contact lies in the laziness or inattention of the electrician who assembles and then maintains the circuit. With a two-wire system, the load on the neutral is not too great. That is why the machine will work much longer. But at 380 V, 3 phases immediately load the neutral contact, which, with poorly stretched terminals, becomes fatal for protective equipment.
To "treat" such a "sore" you should check all zero contacts. The most convenient way to revise the switchboard is to examine it with a thermal imager, on the screen of which problem areas, the temperature of which is higher, instantly become visible. However, units have such expensive equipment, which means that you will have to go throughon all connections and stretch them qualitatively. Particular attention should be paid to the zero bus.
If the revision is made, and after a short time the cut-off device is out of order again, it remains to use the most rational option - to install an automatic input switch 3P (three-pole). However, this is allowed only if there are residual current devices in the circuit that can protect those living in an apartment or house from electric shock. Instead of an RCD, you can use a residual current circuit breaker (RCB).
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 consumption of all household appliances. If we talk about an ordinary apartment, then this figure rarely exceeds 5.5 kW. With such a load, the best option would be to use an introductory circuit breaker 25A. However, this statement is true only for 220 V networks. If the input is carried out via 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 circuit breakers to power equipment up to 5.5 kW, however, the input cut-off must have higher performance.
What to look for when buying a protectiveequipment
When choosing an introductory 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 body of the machine must have a uniform color, without foreign inclusions. Irregularities in the casting should alert the buyer, as well as large gaps in the "flag" area. But the main secret is hidden in one of the sidebars.
The main task of counterfeit manufacturers is to earn as much money as possible. Therefore, they do not bother to install real automation inside the cutter. And here's how you can find out. A real original device has a thick rubber stopper on the side panel. If you pull it out, a bimetallic plate will be found under it, which is responsible for cutting off and relieving voltage from the circuit in case of overheating. So, on counterfeit products, the indicated cork will simply be drawn - it will not be possible to open it.
If you disassemble such a product (it cannot be called an automatic machine), only a contact group will be found inside without any additional elements such as a solenoid, rod or plate. In fact, this is an ordinary switch that is not capable of protecting anyone or anything.
Where is the best place to buy protective automation
Many users claim that online purchases are the most profitable, but this clearly does not apply to the equipment being dismantled today. Indeed, in this caseit is impossible to see the product with your own eyes. It turns out that a person buys a pig in a poke. But not only the safety of the he alth of those living in an apartment or house, but sometimes the lives of people depend 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 an even cheaper product via the Internet - it will most likely turn out to be a low-quality counterfeit.
In conclusion
Choosing an introductory machine is not as difficult 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 line of defense. And if it happens that the rest of the automation fails, you will only have to rely on the introductory cutoff. This means that the home master must be one hundred percent sure of it.
