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When we carry out maintenance, checks, troubleshooting of electrical systems, especially civil and commercial, it can happen to come across conductors of the wrong color. This situation causes two essential problems:
danger to the person who carries out maintenance: an attempt is made to identify the phase and neutral conductors, perhaps the protective conductor (yellow-green) is used for the phase, confusing which conductors are live and which are not, the operator runs the risk of working under voltage even while taking the necessary precautions.
Price rise for modifications, troubleshooting, repairs: the colors of the conductors or cables do not comply with a standard and are randomly placed. How does it come out? You have to arm yourself with enormous patience and understand the circuit, which conductors have been used, how to modify the circuit to solve the problem or add new features. In this way the processing times are much longer because there are no certainties.
So a good system, done properly, would save the customer, the work would be done more quickly, less misunderstandings about the time needed to do even small things (“all this time for so little?“In short, more serenity for everyone. This is valid in general, in any plant, in any situation. The time invested in the beginning to make a good and well documented system, it will save you on all future maintenanceprovided that these too are conducted with the same criterion.
The color of the phase conductors is not imposed, but is recommended by the CEI 64-8 standard, and it is good practice to follow these indications for the reasons just mentioned. Black, brown, gray are used. I am instead mandatory the colors of the neutral conductor and the protective conductor, in jargon the wire earth: the neutral must be blue, the protective conductor must be yellow-green. There is no excuse for yellow-green, it has to be that, terminal strips indicating earth wire or yellow-green colored tape on a wire with another color, even if along its entire length, are not allowed.
For the plants built before 1984 instead they are allowed different colors for the neutral and for the yellow-green conductor as long as it is clamped in every visible and accessible part (it must always be indicated what it is). This derogation, which still creates frequent misunderstandings, concerns installations old of over thirty years which have not undergone any changes or interventions. An analysis of the electrical risk in these systems will certainly advise pulling out the cable and replacing it with an equivalent yellow-green colour, with an evaluation of the earth system and the differentials present.
In summary, where is power present single phase 230V (ex 220) we have the following color of the conductors:
a plug or socket with these conductors is identified with the term 2P+E (2 poles + earth). Instead of black, brown and gray are also used, especially in multicore cables where brown is found instead of black.
Where is power available three-phase 400V (ex 380), we have the following color of the conductors. Note that the phase sequence color is not mandatory as shown in the following figure, but recommended in various variations, the phases can all be of the same color as long as they are suitably signed and indicated in the wiring diagram. The color of the protective and neutral conductor remains mandatory.
A plug or socket with these conductors is identified by the term 3P+N+T (3 Poles + Neutral + Earth).
A plug or socket with these conductors identifies with the term 3P+E (3 Poles + Earth).
When there are multiple phases, these are marked with L1, L2, L3 both at the beginning and at the end of the line. Or R, S, T even if the voluntary standard would indicate as not recommended the letters R, S, T.
As regards single-core cables with sheath (e.g. gray), banding is permitted to identify the neutral and earth conductors, since the sheaths are of the same colour. Attention, they must be tightly bandaged in all accessible points.
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