How many machines to put in the electrical panel: calculation rules
When designing the electrical wiring of a house, performing its replacement or repair, the main attention is paid to safety. The safety of property and the lives of people depend on correctly performed work. To ensure wiring protection, use a circuit breaker. In this article we will tell you how to calculate the number of machines in the shield for an apartment and a private house.
Circuit breaker has two types of protection:
- Provides wiring protection from short circuit. As a result, the currents in the line increase sharply, overheating of the conductors with reflow occurs, and if the currents act for a long time, then with ignition. This leads to a fire, loss of material assets and a life threat is created.
- Protects the line from prolonged exposure to currents higher than rated (protection against overload) As a result, the wires heat up above the permissible value, more than +65 0C. The insulation begins to melt, a short circuit occurs with the ensuing consequences.
The machine is able to provide reliable protection for electrical wiring, equipment, property, is able to preserve human health and life. But it cannot protect a person from electric shock. To do this, apply RCD.
However, in order for the circuit breaker to reliably protect the line, it is necessary to correctly calculate. The industry produces automatic machines of various designs, single-pole, double-pole, three-pole and four-pole.
The figure shows a single-pole, two-pole and three-pole AB.
Calculation of the rating of circuit breakers
When calculating, they are guided by the installed load. From these considerations, the selection of the wire section and the device that will protect the line is made.
For example, we perform line calculations for 3 outlets. It is planned to connect electrical appliances, a washing machine with a power of 2 kW, a microwave of 1.5 kW and an electric kettle of 0.8 kW. The total power is 4.3 kW (4300 watts).
According to the formula, we calculate the current:
I = P / U,
I = 4300/220 = 19.54A
(This formula is valid for active load and is used in the design of electricity in the apartment.)
From the reference tables, select the appropriate wire section. This takes into account the laying method and the material of the conductor. Choose wiring with copper wires.
From the table below, select the closest value. We take a larger section of a copper conductor 2.5 mm2. We will take the values for “laid in the pipe”, because hidden wiring is assumed.
The next step is to select an automatic machine that will be installed in the electrical panel. According to the reference table, we select the necessary circuit breaker.
In practice, outlets use a cable with a cross section of 2.5 mm². Although the table indicates that with an open gasket, 1.5 mm² is also suitable for us.This is more than what we calculated above, and is due to the fact that the cable is laid in the wall, and not in the open air, as well as the features of the operation of circuit breakers - they are ways to pass currents for 13% higher than the nominal. That is, AB on 16A will conduct current for a long time up to 18A, on 25A - up to 28A, etc.
The following is part of the table, with a number of ratings of machine guns manufactured by the industry:
Choose a 16A circuit breaker. According to calculations, the device should be set to 19.54 A. But the industry does not produce such devices, so we select a value lower than the calculated one. In addition, the sockets are designed for a current of 16A, therefore, machines of a higher nominal value cannot be installed regardless of their number.
It will reliably protect the wiring from overload and short circuit currents in an apartment or in a country house. Similarly, the calculation is made when replacing the old wiring in the house.
In other cases, when the connection is made not through an outlet, but directly, like an electric stove, for example, a circuit breaker is selected according to the power of the electric stove. In this case, the cable is chosen so that the rated current can flow through it for a long time, taking into account losses on the line. It is important to note that the permissible continuous current of the cable of the calculated cross-section must be higher by 13% (or more) than the rating of the circuit breaker on this line, for the reasons indicated above.
Calculation of the number of machines
How to calculate the machine on one line, was discussed above. We will calculate the circuit breakers for 1 bedroom apartment.
The figure below shows a typical wiring protection scheme for a one-room apartment:
It follows from it that the individual protection of the lines that feed the end consumers is used:
- Two AVs are installed that protect the lighting lines in the corridor and the room, and the second ensures that the lighting is turned off in the toilet, bathroom and kitchen in an emergency.
- Sockets are protected not only by AB, but also by additional protection on the RCD. It protects a person from accidental contact with live parts of electrical wiring.
- Similarly built protection sockets and washing machine.
- A separate circuit breaker for the electric stove is allocated.
All devices are mounted in an electrical panel. Often it is mounted in the hallway, and an electric meter and an introductory AV are installed on the site.
A 2 room apartment requires a larger number of machines. As can be seen from the diagram below.
Six circuit breakers are mounted in the switchboard, which ensure disconnection of lines in the event of a short circuit or overload:
- one AB protects the lighting line of the corridor and both rooms;
- the second is installed on the lighting of the kitchen, toilet and bathroom;
- Separately protected line that feeds the boiler;
- the next machine protects the outlets of the corridor, room 1, room 2, toilet and kitchen.
Thus, if a malfunction occurs on one of the lines, it can easily be localized and repaired.
In a similar way, the number of circuit breakers for a 3-room apartment or 4 rooms is calculated. At the same time, an electrical panel should be selected, taking into account the number of modules in the box.
The figure above shows the installation of circuit breakers in the electrical panel of a modern apartment.
In front of the circuit breakers, an input circuit breaker is mounted. It protects the wiring of the whole house. As a rule, the value of the input automatic machine is indicated in the power supply agreement and it is impossible to change it to a larger nominal value without appropriate permission (in any case, it is sealed). The input circuit breaker must be mounted upstream of the meter, i.e. protect not only the wiring of the entire house or apartment, but also the meter.
An example is shown in the figure below:
When designing the wiring for a two-story house, they suggest the installation of shields on each floor. Moreover, according to the PUE (chapter 1.2. paragraph 1.2.11) It is recommended to install backup protective AVs and to lay the possibility of developing energy systems.
However, the number of standby machines or machines in the electrical panel as a whole is not regulated by any document. But when designing, it is recommended to install additional machines in the amount of 10%.
Also, if less than 10 automatic machines are installed in the switchboard according to the norm, then an additional reserve one is mounted.
It is not difficult to calculate the number of machines for a house or apartment yourself. You should only adhere to certain rules:
- Knowing the load current, the wire cross section is selected in a larger direction, and the machines are selected at a lower current.
- Introductory AB is calculated limited by the power allocated to your facility.
- The number of machines is calculated by the number of wiring lines and consumers.
The calculation of the number of circuit breakers must be done carefully. Not only the preservation of material values, but also human life and health depends on this. Therefore, it is recommended to entrust the calculation to qualified specialists.