The subject of neutral conductor color always generates discussion among electricians, some based on the norm, others not so much. In this article we will show what the NBR 5410 standard says about neutral conductor color, whether or not it can be black. In case you do not find a conductor with blue insulation to buy, can the work be done with black or other colored cables?
What is the Neutral conductor?
The neutral conductor is an element of the circuit or of a certain system, which presents the electric current and the null electric potential difference, regardless of its shape or nature. But even with these characteristics, the neutral conductor can be an active conductor, that is, at some time or situation the electric current and electrical voltage in the neutral conductor may not be null.
The neutral conductor is essential in electrical installation, especially for low voltage installations. The neutral conductor in residential, building or industrial electrical installations is essential because it is through the neutral that we can obtain different voltage levels, such as 127 V or 220 V , which will also depend on what voltage the concessionaire in each region supplies to the consumer.
Are Positive, Negative and Phase, Neutral the same thing?
It is wrong to think that the positive, negative, phase and neutral cable are the same things. The terms positive and negative are used in direct current circuits, where the poles are defined, that is, positive and negative pole, thus the current direction over time remains constant. The direct current is obtained through batteries, batteries, power supplies, chargers, etc.
The phase and neutral cable are present in alternating current circuits, where there are no fixed poles defined as in direct current. In alternating current, the direction of current varies over time, and is usually obtained through alternating generators.
Black Neutral cable can?
We know the importance of knowing and consulting the NBR 5410 standard . The standard deals in item 220.127.116.11 exclusively with conductor colors and in item 18.104.22.168.1 deals exclusively with the color of the neutral cable.
The item says that any isolated conductor, unipolar cable or vein of multipolar cable used as a neutral conductor must be identified according to this function. In case of color identification, the light blue color must be used in the insulation of the isolated conductor or the vein of the multipolar cable, or in the cover of the unipolar cable.
In the sequence there is a note that says that the vein with light blue insulation of a multipolar cable can be used for functions other than the neutral conductor, if the circuit has no neutral conductor or if the cable has a peripheral conductor used as neutral.
The standard is very clear that any cable can be used as neutral, but it must be properly identified. One of the ways to identify the cable is by color, in this case light blue must be used, but in the absence of the light blue cable the colored insulating tape (blue) or identification with use of washers (n).
We did a quiz on instagram at Mundo da Elétrica, about the color of the neutral cable. The quiz question was based on the same style as the questions that are asked in competitions or selection processes of companies, where the question was:
According to NBR 5410, can a neutral cable be black?
The alternatives are:
A) No, under no circumstances.
B) Yes, if it is identified in all the pass boxes
C) Yes, if the neutral cable is thicker than the phase cable.
D) Yes, but it should only be identified in the QDC.
Which alternative would you choose? Knowing that the standard does not prohibit a neutral cable from being black, as long as the cable is properly identified. Comment here in the comments which one you would choose and why.
The correct answer would be alternative B), because the pass boxes are where the conductors are most visible and is accessed for maintenance, we know that the good practices of electrical installations recommend the identification of cables by color to make life easier for the professional that does maintenance.
Below we have a video of the World of Electrical showing the color pattern of the phase, neutral and earth cables according to the NBR 5410 standard.