Electrical projects are undoubtedly one of the biggest challenges for many electricians, thinking about it we decided to leave some tips on reading and interpreting electrical diagrams, but before that, it is necessary to have some knowledge about the types of diagrams. We will approach a little about each of the types of diagrams, as their characteristics, symbols, and care that must be taken. Come on, guys!
It is important to highlight that we have them as main objective to clarify the main doubts about electrical projects for low voltage installations, due to a large amount of information and details that would be necessary to address the other areas.
Many electricians, when they hear about an electrical plant, electrical diagram, electrical schematic or electrical project, are very insecure, as they may not have a certain command over this subject.
What is electrical design:
The electrical project is the combination of all information regarding the electrical part of an electrical installation, machine or equipment, these data can be contained in the form of electrical data tables, electrical diagrams, component distribution schemes, electrical plants, layout and etc.
It is very common when we hear about electrical design that we immediately think of a residential electrical project, or residential electrical plant, which is usually a diagram with the distribution of cables, placement of sockets and lamps, which are drawn on the floor plan of a house, building or shed for example.
Any electrician can not only know how to read and interpret an electrical diagram, even perform calculations of electrical projects, make drawings, layouts and create the tables of an electrical project, but only the technician or engineer who is registered with the Regional Engineering Council and Agronomy (CREA) can be technically responsible for an electrical project.
The electrical diagram is a set of graphic symbols, these symbols are capable of representing an electrical installation or part of one of the installation, since the electrical diagram guarantees a common language for any electrician, as the drawing is a visual representation capable of being understood in any place in the world.
There are four types of diagrams, which are: single-line diagram, multi-line diagram, three-line diagram and functional diagram. The diagram most used for residential electrical projects is the single-line diagram.
The single-line diagram, which is also known as the electrical plan, is drawn on the floor plan (architectural plan) of installation and it presents the devices and the path of the conductors in their physical positions in a precise way, despite being a two-dimensional representation.
The single-line diagram is especially useful for checking, quickly, how many conductors will pass through certain conduits and their paths.
A difference from the single-line diagram to the multi-line and functional diagrams is that all conductors on the same path are represented by a single dash, which contains some symbols that serve to identify all conductors
In the single-line diagram, the operation of the installation is not clearly represented. According to the practice acquired by the electrician over time, he starts to easily interpret an electrical installation and without the aid of other diagrams.
Understanding the residential electrical diagram.
We will divide the single-line diagram into two parts, first we will show the diagram with only one lighting circuit, and then with the lighting circuit and outlet circuit.
Diagram for lighting circuits
Lighting circuits are the ones that usually cause more doubts among electricians, both when drawing the diagram and when reading the single-line diagram, mainly because of the return cables and the neutral cable, which many electricians take to the switch, unless it also has a plug point.
One section switch:
The image that we show below has the representation of two rooms of a determined installation, where we have represented in the diagram only a single point of illumination, and this point is controlled by a simple switch.
We highlight in the image above the letters that are indicating the lighting circuit, with the letter “a” being represented above the lighting point, at the switch point and above the return conductor, this is to identify and facilitate the reading of all lighting points in the circuit, that is, all points containing the letter “a” are related to the same lighting circuit.
There are other symbols that are being represented in the diagram above, as is the symbol highlighted in green, because it represents which circuit that connection belongs to, which in this situation is easy to identify, but in larger installations or that has more circuits without the necessary indications difficult to identify.
The image shown below is for an even larger installation, which contains two different lighting points, which are being controlled by a single two-section switch , see that the points are properly represented with the letters “a” and “b”.
Parallel switch (three way):
The representation for the connection of the three way switch is a little different, which ends up generating a lot of doubts, in the image below it shows a phase cable, a neutral cable and another earth cable arriving at the lighting point. Then we have a phase cable going to a switch and to the other switch we have the return cable, both switches are directly interconnected, so much so that their symbology is of two crossed return cables, which are properly represented in the image below .
Intermediate switch (four way):
This connection is undoubtedly the most difficult to understand, due to the number of connections. The basis for connecting the intermediate switch is a three way switch, but in the middle of the way we have the four way switch, which is the third point.
The basic representation consists of two three way switch returns, with two return cables connected directly to their respective parallel switch terminals, the other two return cables are connected directly to the other two intermediate switch terminals.
We will show the wiring diagram for connecting general purpose sockets (TUG) and specific use sockets (TUE), we will be using the same diagram as the lighting circuit, but with an outlet circuit. The image below shows three points of sockets on a second circuit.
The first difference we can observe is that in an conduit two circuits are passing, one for lighting and one for the sockets, each circuit having a phase cable, a neutral cable and a ground cable, that is the total of six conductors passing through a single conduit and reaching the ceiling lighting point.
The ceiling lighting point is where the circuits are separated, to one side the socket circuit and to the other the lighting circuit. It is important to note that each time an conduit passes through a component, the phase, neutral, earth and circuit symbols they belong to must be indicated, as shown in the image below.
As we saw earlier, just like all cables that pass through an conduit have the indication of the circuit they belong to, all sockets must also have indications of their respective circuits. In addition, when we have a socket on the circuit that is not for general use, it is necessary to indicate its power and the respective circuit, as we can see in the representation below.
Circuit of TUG and TUE sockets.
In this diagram we will leave the 600W socket as a third circuit for a specific use socket. As we can see, there are three circuits passing through the conduit that is being led to the lighting point on the ceiling, notice the image that is represented below that there are three circuits represented with the phase, neutral and ground cables, that is, there are nine conductors passing through this conduit, where the circuits are being separated.
In this article we show some symbologies and connection schemes, but it is important to note that not all symbologies or connection possibilities have been represented, as there are still other ways to represent the same components. Therefore, learning to read and interpret electrical diagrams is not a very simple task, but one that is mastered over time, with much practice and study.