When a person assembles an electrical panel or wants to connect a new powerful household appliance, it is important to choose the right circuit breaker. They allow you to basically avoid the dangerous actions of power surges, a fire that can happen in the event of these surges. In more detail about the functions of electrical switches, how to choose a circuit breaker, in particular, to select automatic machines for an apartment according to the load - we will tell in the article.
Circuit breaker functions
Simply put, such a switch automatically works in two cases:
- current overload;
- short circuit (short circuit).
The first case occurs when the equipment that is powered is faulty, and produces current indicators above the norm - if not turned off, the equipment can catch fire and cause a fire. Also, overcurrent occurs when there are too many consumers in the apartment.
The second case is when the power of the electrical circuit is spent on heating the wires.
In addition to automatic protection, there is the possibility of manual shutdown. For example, a person needs to change a light bulb in a room. Then he turns off the machine in the shield, which supplies current to the room, and you can safely replace the lamp.
Number of circuit breaker poles
Circuit breakers according to the number of poles are:
- Unipolar. One wire is connected to such a device - a terminal on top and a terminal on the bottom. An automaton of this type is needed to protect one phase.
- Bipolar. They look like two machines combined into one. When the current in one phase exceeds the allowable value, two power lines are turned off at once.
- Tripolar. The same as bipolar, only three phases pass through one device at once.
- Four-pole. They are usually used as the main circuit breaker - at the input of the electrical panel.
On devices with several poles, the handle-switch is the same for all phases.
Rated current of circuit breaker
There are several types of automatic shutdown devices in terms of rated current - from 0 amperes to 5 amperes. Upon reaching the phase current above the specified rating, protection is triggered - the handle-switch goes down, the circuit is de-energized. However, the machine does not always work instantly. In its characteristics there is such a value as the time-current characteristic. Depending on the functions of the device, it works instantly or not:
- In the case of protection against current surges - it is also called thermal protection - the machine works a minute after the current exceeds the nominal value twice.
- On type B machines - to turn off the current rating must be 3-5 times higher, A - 2 times, in type C - 6-10 times. There is also type D, but such an automatic machine is not used in apartments.
Which circuit breakers to choose? For an apartment, type C machines are most often installed.
On the machine, the time-current characteristic is marked, for example, as follows: 6A, 10D, 32C, etc. The number indicates the rated current.
Now let's look at how to make a choice of a circuit breaker according to the load.
Choice of circuit breaker according to load power
The selection of automatic machines for an apartment according to the load consists of two stages:
- We find out the power and current of the equipment of the apartment - lighting, refrigerator, microwave, iron, kettle, etc. The current is calculated using the formula I=P/220. P - power, which can be found in the instructions for home equipment. It will only be necessary to add up all the powers. Then we find out the current by the formula. So, for a refrigerator of 75 watts, the current will be 0 amperes.
- We choose such an automaton so that it accurately protects the phases from overloads. If, for example, the amount came out 3 Amperes, then the machine should be exactly 3 Amperes.
For an apartment, we advise you to choose an automatic machine of type A - if the sum of currents is 10 Amperes, then the automatic machine should be selected for 10 Amperes.
Or you can make the choice of automatic machines for an apartment easier: to protect sockets, they usually choose automatic machines for 16 Amperes - 16A, for lighting - 10A.
The choice of the machine for the cable section
It's one thing when, for example, you need to replace an old Soviet machine gun with a new one. Another thing is if an electrician or the owner of the dwelling himself does the wiring and installs electric machines for the apartment. Then you need to count according to such a table, which indicates the cable cross-section and the desired machine:
Cable section, sq. mm
Rated current of the machine, A
Power of 1-phase load at 220V, kW
In any case, a practicing electrician knows better which electric machine or electric machines to choose. It's best to check with him before buying.