Residential electrical scheme. Learning step by step!

When performing a residential electrical installation, having the residential electrical installation scheme in hand makes all the difference, as it is a manual of electrical installations and also a great differential for the electrician. Find out what are the differences between a residential electrical scheme and a residential electrical diagram, as well as learn tips on electrical schemes that are essential for the electrician. Come on, guys!

What is an electrical scheme and what is it for?

The electrical diagram is essential to perform any installation, it is basically the graphic representation of the electrical and electronic circuits, the electrical diagram is also a guide for the execution of the entire installation, so that it facilitates during the execution of this installation, allowing more safety and reducing the possibilities of errors, in addition to helping to find problems and abnormal situations in the circuit.

Electrical diagrams or electrical diagrams?

An electrical diagram is a drawing that shows how a particular installation is made, but it is not necessarily an electrical diagram. The wiring diagram may not be very complex, but it is useful and important in an installation. Although they are not the same thing many professionals are in doubt.

Electric scheme:

To exemplify, we will make an electrical scheme step by step of a house, so that there is no doubt.

It is important to remember that the dimensioning of the conductors outside the installation is the responsibility of the concessionaire, while the customer is responsible for the meter inside the installation.

The diagram below is for the simplest possible residential electrical installation, whose power supply is 127V, having three circuits, which are: outlet circuit, lighting circuit and a circuit only for the shower.

The layout of a simple residential installation.

When starting to make the electrical scheme be as organized as possible, because of the bigger the organization the better the understanding. Remembering that this is just a simple circuit, more complex ones will require more attention and organization.

The power cables that are between the meter and the circuit distribution board (QDC) are of greater gauge or thickness, as they pass through all the electrical current of the installation. Even if the sum of the powers of the respective loads is the same, the cable section may vary, as it will depend on the supply voltage.

When arriving at the circuit distribution board, the electrical installation must be divided into separate circuits so that each one is dimensioned according to its loads. The separation of the circuits must be done in order to reduce the consequences of a failure that will cause only the sectioning of the circuit in which a defect occurs.

In installations where there is no distribution of the circuits, any failure can cause the general circuit breaker to be disconnected, but this is still at best, because if there is a short circuit that is not detected by the general circuit breaker, in this installation a fire may end up occurring. .

Performing this distribution will also facilitate the checks and maintenance, if there is not possible to verify part by the electrical installation, this procedure helps a lot to find the exact point of the failures.

The total load must be divided in order to build circuits of close power, as they guarantee a current balance between the circuits. In installations where there is more than one phase distributed between the circuits, this balance is very important, even so that one of the breaker poles does not heat unevenly or that one of the phases is overloaded.


Although the scheme above has made the separation between lighting circuit and socket, the NBR 5410 standard allows that in housing installations, the lighting points and sockets can be powered by the same circuit as long as it meets three criteria, which are:

  • The total electrical current of this circuit (socket and lighting) does not exceed 16A.
  • All lighting points are not powered by a single outlet and lighting circuit.
  • The outlet points are not all powered by a single outlet and lighting circuit.