Collecting electrical panels or connecting new large household appliances, the home master will necessarily encounter such a problem as the need to select circuit breakers. They provide electro and fire safety, because the right choice of the machine is the security deposit of you, family and property.
What is the machine
In the power supply circuit, the machine is set to prevent wiring overheating. Any wiring is designed to pass any specific current. If the current current exceeds this value, the conductor begins to warm too much. If such a situation persists a sufficient period of time, the wiring starts to melt, which leads to a short circuit. The protection machine is put to prevent this situation.
Package or automatic protection need to prevent overheating of conductors and shutdowns in the case of KZ
The second task of the protection automaton - when the short circuit current occurs (KZ), turn off the power. When closure, currents in the chain increase repeatedly and can reach thousands of amps. So that they do not destroy the wiring and did not damage the equipment included in the line, the protection machine must turn off the power as quickly as possible - as soon as the current exceeds a certain limit.
For a protective circuit breaker to fulfill its functions, it is necessary to properly make a choice of automaton in all parameters. They are not so much - only three, but every one should understand.
What are the protection machines
To protect the conductors of a single-phase network of 220V, there are disconnecting devices of single-pole and bipolar. Only one conductor is connected to one-pole, phase, to a two-pole and phase and zero. Single-pole machines put on the circuit 220 in the internal lighting, on the sockets in rooms with normal operating conditions. They are also put on some types of load in three-phase networks, connecting one of the phases.
For three-phase networks (380 V) there are three and four poles. These are these protection machines (the correct name of the circuit breaker) put on a three-phase load (oven, cooking panels and other equipment that runs from the network 380 V).
In rooms with high humidity (bathroom, sauna, swimming pool, etc.) put two-pole circuit breakers. They are also recommended to install on powerful techniques - on washing and dishwashers, boilers, brass cabinets, etc.
Simply in emergency situations - with a short closure or test of insulation - a phase voltage can get to the zero wire. If a single-pole machine is installed on the power line, it will turn off the phase wire, and the zero with a hazardous voltage remains connected. So, there remains the likelihood of damage to the current when touched. That is, the choice of the machine is simple - single-pole switches are put on some of the lines, the part is two-pole. A specific amount depends on the state of the network.
Machines for single-phase network
For a three-phase network, three-pole circuit breakers exist. Such an automatic is placed at the entrance and on consumers, to which all three phases are mounted - electric stove, three-phase cooking panel, oven, etc. For other consumers, two-pole protection machines are put. They must necessarily turn off the phase and neutral.
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Example of a two-phase network layout - Types of protection machines
The choice of the nominal protection automaton from the number of wires connected to it does not depend.
We are determined with the par
Actually, from the functions of a protective machine and follows the rule of determining the nominal protection machine: it should be triggered until the current exceeds the possibility of wiring. And this means that the current rating of the machine must be less than the maximum current that stands the wiring.
Each line requires the correctly choose the protection machine
Based on this, the algorithm for choosing a protective protection machine is simple:
- Calculate the wiring section for a particular area.
- See which maximum current withstands this cable (is in the table).
- Next, from all the ratings of protective automata, choose the nearest smaller. Automatom Nominations are tied to permissible long-term load currents for a particular cable - they have a little smaller nominal value (there is in the table). It looks like a list of denominations as follows: 16 A, 25 A, 32 A, 40 A, 63 A. Here is from this list and choose the appropriate. There are denominations and less, but they are already practically not used - we have too many electrical appliances and they have considerable power.
Example
The algorithm is very simple, but it works unmistakably. To be clearer, let's look at the example. Below is a table in which the maximum allowable current for the conductors, which are used when laying wiring in the house and apartment. There are also recommendations regarding the use of automata. They are given in the "Nominal Current Nomotor" column. It is there we are looking for a nominal - it is a little less than the maximum permissible that the wiring worked in normal mode.| Copper wire section | Permissible long load current | Maximum load power for single-phase network 220 V | Nominal Protective Current | Protective Machine Current | Approximate load for single-phase chain |
|---|---|---|---|---|---|
| 1.5 square meters. MM. | 19 A. | 4.1 kW | 10 A. | 16 A. | Lighting and alarm |
| 2.5 square meters. MM. | 27 A. | 5.9 kW | 16 A. | 25 A. | Outlet groups and electric warm floor |
| 4 sq.mm. | 38 A. | 8.3 kW | 25 A. | 32 A. | Air conditioners and water heaters |
| 6 sq.m. | 46 A. | 10.1 kW | 32 A. | 40 A. | Electric stoves and brass cabinets |
| 10 square meters MM. | 70 A. | 15.4 kW | 50 A. | 63 A. | Introductory lines |
In the table we find the selected cross section of the wire for this line. Let us be necessary to pave a cable with a cross section of 2.5 mm2 (the most common when laying to the instruments of the average power). The conductor with such a cross section can withstand the current at 27 A, and the recommended nominal model - 16 A.
How will the chain then work then? As long as the current does not exceed 25 and the machine does not turn off, everything works in normal mode - the conductor is heated, but not to critical quantities. When the load current begins to increase and exceeds 25 A, the automatic is not turned off for some time - it is possible that starting currents and they are short-lived. It turns off if a sufficiently long time the current exceeds 25 A by 13%. In this case, if it reaches 28.25 A. Then the electropacate will work, de-energized the branch, as this current is already a threat to the conductor and its isolation.
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Calculation of power
Can I choose a load capacity machine? If only one device is connected to the power line (usually large household appliances with high power consumed), then it is permissible to make the capacity of this equipment. Also, in terms of power, you can choose an introductory machine that is installed at the entrance to the house or apartment.
If we are looking for a nominal nominal machine, it is necessary to fold the power of all the devices that will be connected to the house network. The following total power is substituted into the formula, is a working current for this load.
Formula for calculating current by total power
After found a current, select the nominal. It can be either a little more or a little less than the value found. The main thing is that its shutdown current does not exceed the maximum allowable current for this wiring.
When can this method be used? If the wiring is laid with a large stock (it is not bad, by the way). Then, in order to save it, you can install the automatically switches corresponding to the load, and not the cross section of the conductors. But once again we draw attention to that a long-permissible current for the load should be larger than the limiting current of the protective automaton. Only then the choice of the automatic protection will be correct.
Select the disconnecting ability
The above describes the selection of the packet on the maximum permissible current current. But the network protection machine must also turn off when the short circuit occurs from the short circuit). This characteristic is called a disconnecting ability. It is displayed in thousands of amps - registered such order can reach currents with a short circuit. The selection of the disabled ability is not very complicated.
This characteristic shows how the maximum value of the current CW automatically saves its performance, that is, it can not only turn off, but will also work after re-inclusion. This characteristic depends on many factors and for accurate selection it is necessary to determine the currents of the KZ. But for wiring in a house or apartment, such calculations are made very rarely, but are guided by remoteness from the transformer substation.
Disconnectivity of automatic protective switches
If the substation is located close to entering your home / apartment, take an automatic with a disconnecting ability of 10,000 A, for all other urban apartments 6,000 A. If the house is located in the countryside, you choose the power supply automatic for giving, may well be enough And the disconnecting ability of 4,500 A. networks here is usually old and currents of the KZ are not large. And since with an increase in the disconnecting ability, the price increases significantly, you can apply the principle of reasonable savings.
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Is it possible to put bags with a lower disabling ability in urban apartments. In principle, it is possible, but no one guarantees that after the first KZ you do not have to change it. He may have time to disable the network, but it turns out to be inoperable. In the worst version, the contacts are melted and the machine will not have time to disconnect. Then the wiring melts and may arise.
Type of electromagnetic release
The machine must trigger when the current is raised above a certain mark. But the network periodically arises short-term overload. Usually they are associated with starting currents. For example, such overloads can be observed when the refrigerator compressor is turned on, the washing machine motor, etc. The circuit breaker at such temporary and short-term overloads does not have to disconnect, because they have a specific trigger delay.
But if the current has increased not due to overload and because of the CW, then in the time that the automatic switch is "waiting", the contacts are melted. Here for this and there is an electromagnetic automatic release. It is triggered at a certain amount of current, which can no longer be overload. This indicator is also called the cut-off current, since in this case the circuit breaker cuts off the power line. The value of the trigger current can be different and displayed by letters that stand in front of the numbers indicating the nominal machine.
There are three most running type:
- B - triggers when the rated current is exceeded 3-5 times;
- C - if it is exceeded 5-10 times;
- D - if more than 10-20 times.
Machine class or current cut-off
What is the characteristic to choose a packet? In this case, the choice of the automaton of protection is also based on the remoteness of your home ownership from the substation and the state of the power grid. The choice of a protection machine is carried out creeping up simple rules:
- With the letter "B" on the housing are suitable for cottages, villages of villages and villages that are used through the air. You can also put them in the apartments of old houses, in which the reconstruction of the domestic power grid was not produced. These protective machines are far from always available, it is a bit more expensive category C, but can be delivered under the order.
- Paktniki with "C" on the housing is the most widespread option. They are put in networks with a normal state, suitable for apartments in new buildings or after overhaul, in private homes near the substation.
- Class D put in enterprises, in workshops with equipment having high starting currents.
That is, in fact, the choice of a protection machine in this case is simple - for most cases the type C is suitable. It is in stores in a large assortment.
What manufacturers should trust
And finally, we will pay attention to manufacturers. The choice of the machine cannot be considered completed if you did not think about what kind of firm circuit breakers you will buy. It is not necessary to take unknown firms - the electrician is not the area where it is possible to put experiments. Details about choosing a manufacturer in video.