Switching automation of the home power network has been and remains the most important stage of electrical work. However, before proceeding with it, it is necessary to select the equipment in such a way that it can protect the wiring from overloads and short circuits. If all calculations are performed correctly, then the shutdown will occur when necessary, and not spontaneously. Although even worse, if there is no cut-off at all, this is fraught with huge problems. In today's article, we will talk about how to choose a circuit breaker in terms of power, current strength and other parameters of the electrical network.
Why protection is needed and how it is carried out
If many consumers are connected to one outlet and the load on the wire exceeds the permissible limit, the cable starts to heat up. This may cause ignition of the insulation and fire. The same happens during a short circuit, but the heating process in this case proceeds rapidly, almost instantly. To prevent such emergencies, circuit breakers are installed, the features of the selection of power of which will be considered today.
Their work is as follows. A static solenoid is located inside the AB, through which current flows. A moving rod is located in the center of the coil. When an overcurrent occurs in the solenoid, a strong electromagnetic field arises. It is it that pushes the rod, which presses on the foot, resulting in a cut-off. A bimetallic plate is responsible for turning off the voltage during overheating in the machine, which changes shape with increasing temperature.
The consequences of improper selection of the machine
Some home masters who do not have electrical installation experience believe that it is better to purchase an AV of a higher nominal value than to make the necessary calculations. This is a rather dangerous misconception that can lead to loss of property or even life. The fact is that if you purchase a large-value AB, without observing the rules for calculating circuit breakers, the following may happen. Overload on the line leads to heating of the wire, while the solenoid does not respond to it. Further, the wire in the region of the outlet heats up to a critical temperature, the insulation ignites. Wallpaper and furniture light up from it. Burnt insulation, of course, leads to a short circuit and voltage cutoff, but this action is already meaningless - the fire has already begun.
Now another, less terrible, but rather unpleasant mistake - the rating of the machine is lower than required. When working on the line of one consumer, everything is in order, but it is worthwhile to include in addition, for example, a mixer or a food processor, a cut-off occurs, the voltage disappears. It is worth considering whether it will be comfortable to live in such conditions? Or is it easier to calculate everything correctly once?
How to make calculations correctly: first steps
Any electrical equipment consumes a certain power. These data are contained on the nameplate of the household appliance and in its technical documentation. Before you calculate and choose a circuit breaker, you need to write out the power consumption of each of them on a sheet and add. It is on the basis of these data that calculations are made.
We will make a similar calculation of the kitchen outlet group. For example, it is planned to connect a microwave oven (800 W), an electric kettle (1000 W), a dishwasher (2000 W) and a refrigerator (600 W). It turns out that the total consumption of the outlet group (P) will be equal to 4400 watts. But you need to choose a current circuit breaker. What to do if only the power consumption is known? It's not a problem. It is necessary to calculate the current load according to the formula I = P / U, where U is the voltage in the network. We get: 440 ÷ 220 = 20 A. In the line of manufactured machines there is just such a value, which means that an AB with a rated current of 20 A is perfect.
But these are not the only calculations that need to be done for AB to work correctly. Choosing a circuit breaker in terms of power and current, you need to determine the cross-section of the wire, which is necessary for the normal power supply of household appliances connected through this outlet group.
What could be wrong with wires
Quite a common situation: the new owner of the apartment makes repairs. Sockets are changing, protective automation is ideally selected for installed household electrical appliances. However, subsequently, the smell of burning insulation appears, while AB does not react to heating (and, therefore, overload). Why it happens? The problem is that the old wiring does not withstand the load that the machine is designed for. A small digression should be made here.
The home master should understand that the circuit breaker is not intended to protect household appliances. Its task is to ensure stable operation of the wiring. Therefore, when choosing a machine for power, you should decide on a cable that is suitable for the cross section. Only with the full interaction of all nodes the circuit will function normally.
Section selection and how to produce it
For the correct selection of wires for this parameter, you should again refer to the total power consumption. In the example of a kitchen outlet group, this figure was 4400 watts. Now you need to turn to the section table - it can easily be found on the Internet. The closest value available in it is 4600 watts. To power devices of such power, a copper wire with a cross section of 2.5 mm 2 or aluminum - 4 mm 2 is required. Only in this case, we can hope that the machine will shut off during overloads that are dangerous to the wire.
And from the video below you can learn a little more about the selection of AB.
What if there is no way to replace the wires?
Often the question arises, how to calculate and choose a circuit breaker, leaving the old cables in place. In this case, the only right decision would be the selection of AB based on the cross section of the wire. This is the only way to be sure of safety. Then, when more consumers are connected to the sockets than the cable can withstand, protection will work.
In general, judging by user reviews, such problems are quite common. That is why people have to use the devices separately, of course, until the complete replacement of the wiring.
Some tips on choosing the right circuit breaker
Taking into account the fact that the number of household appliances is constantly growing, it is better to install the machine immediately a little more power, but only on condition that the cables will be with an increased cross-section. On the Internet there are many "craftsmen" advisers who say that if the machine does not withstand the increased load, you just need to put the device more powerful. In no case. After all, then the wiring for which it is intended can not withstand.
How to choose a circuit breaker for home, apartment? In the store, the device you like should be carefully inspected. Now on the shelves there are quite a lot of counterfeit products, the bulk of which can be easily determined visually.
How to recognize a fake
The first thing you should pay attention to the side wall of the machine. It has a rubber stopper that can be pulled out. A bimetallic plate will be visible below it. Those who produce fakes try not to invest in production, and therefore instead of a rubber stopper on the case there will be a painted one that cannot be opened. Naturally, there is no question of any bimetallic plate inside. There is nothing at all except a disconnect switch. In fact, this is a normal switch, not capable of any protection.
Also, before choosing a circuit breaker in terms of power, current or cable cross-section, it is worth paying attention to its appearance. Should alert:
- foreign inclusions in the plastic of the body;
- color unevenness, stains;
- uneven seams;
- fuzzy printed information on the front side;
- large gaps between the lever and the body.
If such defects are found, it is better to refrain from acquiring.
A little more about automation: some recommendations
Protecting your home electrical network is not limited to installing one AB. It should be understood that the load of the entire apartment should not go through one circuit breaker. Of course, sometimes it seems that there is no other way out, especially for old-built houses. However, this is completely wrong. Entering the apartment and realizing that the protection system is no good, it is better to take care of this in the first place and replace the wiring. Do not save on your safety. The action algorithm should be as follows.
To begin with, the wires going to the apartment are completely disconnected from the introductory machine, and an extension cord is connected instead. Now you can not be afraid that when the walls are gated, a short circuit will occur. After that, you can safely prepare the channels for laying cables. To do this, you can use a conventional hammer drill or a special tool - an electric chipper.
After making the calculations, the necessary material is purchased - wires, AB (now it is known how to choose a circuit breaker by power). Power supply to cables is made only after full installation. Live wires are not allowed. For wiring, it is better to use copper cables. Despite the higher cost, they allow the use of a smaller section (which means they are easier to install). In addition, copper is much more durable than aluminum. There are cases when cheap wires scattered after 10 years of operation.
If you plan to install household appliances with high power (electric stove, water boiler), it is better for them to draw a separate line from the input machine.
Why the machine shuts down for no reason
Similar, if emergency situations such as overload and short circuit are excluded, it can only happen due to the fact that the AB has fulfilled the prescribed operation cycles. In this case, you have to go to the store for a new one. Some argue that if you carefully open the failed AB, it can be completely restored, but this should not be done. Today it was talked about how to choose a circuit breaker in terms of power. So, in the case of an attempt to repair the old AB, even if it was successful, you can forget about it. Such a “switch” (you can’t even call it an automaton) can fail at the most crucial moment.
Finally
Choosing a circuit breaker is a responsible matter. And the work of all the protective automation of the home electrical network, and, therefore, the safety of property, and possibly life, will depend on how much the home master takes it seriously.