In this post we will analyze the different cases that occur in the low voltage installations, the main points that are established in the Low Voltage Electrotechnical Regulation, the interpretation of the single-line diagram of a house as well as the circuits basic that compose it. To design electrical installations, it is important for us not to do them manually or by hand. We should use a software designed specifically for it. Electronic CAD software is the most appropriate answer and we can rely on IGE-XAO for it. This software is designed specifically for use by any electrical engineer. For more details visit http://www.ige-xao.com/en/software-editor-electrical-plm-cad-and-simulation/electrical-cad-software is highly recommended.
Distribution of the current
According to the Low Voltage Electrotechnical Regulation, the nominal voltages that are generally used in the alternating current distributions are established.
It is established that the nominal voltages usually used in the alternating current distributions will be:
– 230 V between phases for 3-wire three-phase networks.
– 230 V between phase and neutral, and 400 V between phases, for three-phase networks of 4 conductors.
It also indicates that the frequency used in the network will be 50 Hz.
At this point, we would have to calculate the maximum current of our installation, according to the installed power in our installation.
P = V I (Complex power)
The complex power, which has two components, an active power (consumed in the resistances in its majority) and reactive (developed in inductive circuits).
Degree of electrification
In the first place, when an electrical installation is going to be designed, a study of the electric charges that are foreseen will be carried out. Thus, to know the electrical load of an installation, we will have to know the power of all the receivers that are going to be installed and connected at the same time (simultaneity).
The sum of these powers, will lead to the loading of the installation. However, this can not be known a priori on many occasions, which is why the regulation establishes the degree of housing, which depends on the degree of use desired. The following degrees of electrification are defined:
– Degree of basic electrification: it is the necessary one for the coverage of the possible needs of primary utilization without need of later works of adaptation. It must allow the use of electrical appliances commonly used in a home.
– Degree of high electrification: corresponds to homes with a forecast of use of electrical appliances greater than basic electrification or with provision for the use of electric heating or air conditioning systems or with useful living space of more than 160 m2, or with any combination of the above cases. Different room spaces may require different electrical schemes associated with energy supply systems.
The user will determine in agreement with the supplying company the power to be foreseen, which, for new constructions, will not be inferior to 5.750 W at 230 V, in each dwelling, independently of the power to be contracted by each user, which will depend on the use let him do the electrical installation.
In homes with a high degree of electrification, the power to be provided shall not be less than 9,200 W. In all cases, the power to be provided shall correspond to the maximum capacity of the installation, defined by the assigned intensity of the automatic main switch. In addition, the load corresponding to the housing unit must be taken into account, in order to calculate the supply of the entire building.
Single and multi-wire diagram
The electrical installations, for a quick and simple interpretation, are represented by schemes that incorporate the different elements found throughout the installation.
The single-line diagrams are used as the first contact plane with the installation, giving us a general idea of this as well as the situation of the elements and the degree of electrification therefore of the same. In this, basically the lines, breakers and water switchgear below the main power supply are shown.
The multifilar schemes are those that arrive at the detail of the installation, giving us a broad idea of the operation, execution of the wiring and therefore a quick and easy repair in your case.
According to the regulation, the following types of independent circuits are defined and each will be protected by an omnipolar automatic circuit breaker with manual operation and protection devices against overloads and short circuits with an intensity assigned according to its application and indicated in section 3. Depending on the degree of electrification we will have:
C1 internal distribution circuit, designed to power the lighting points.
C2 internal distribution circuit, intended for general and refrigeration power outlets.
C3 internal distribution circuit, intended to power the kitchen and oven.
C4 internal distribution circuit, designed to feed the washing machine, dishwasher and electric water heater.
C5 internal distribution circuit, intended to feed power outlets of the bathrooms, as well as the auxiliary bases of the kitchen room.
This is the case of homes with an important forecast of household electrical appliances that requires installing more than one circuit of any of the types described above, as well as with provision for electric heating systems, air conditioning, automation, technical management of energy and security or with useful surfaces of homes over 160 m2. In this case, in addition to those corresponding to basic electrification, the following circuits will be installed:
C6 Additional circuit of type C1, for every 30 points of light
C7 Additional circuit of type C2, for every 20 electrical outlets of general use or if the usable floor area of the house is greater than 160 m2.
C8 Internal distribution circuit, intended for the installation of electric heating, when there is a forecast of this.
C9 Internal distribution circuit, intended for the installation of air conditioning, when there is a forecast of this
C10 Internal distribution circuit, intended for the installation of an independent dryer
C11 Internal distribution circuit, intended for powering the automation system, technical management of energy and safety, when there is a forecast of this.
C12 Additional circuits of any of the types C3 or C4, when provided, or additional circuit of type C5, when their number of sockets exceeds 6. For both basic and elevated electrification, it shall be placed, as a minimum, a differential switch.
Distributing circuits is not a simple task and for such matters, using the best Electronic CAD software is highly recommended. For more information, visit http://www.ige-xao.com/en/software-editor-electrical-plm-cad-and-simulation/electrical-design-software.