PlantFlow 3D › Guides › Electrical wire colours and wire numbering in control panels
Electrical wire colours and wire numbering in control panels
IEC conductor colours for three-phase and control circuits, how wire numbers and ferrules work, and why the same number means the same potential.
IEC colours for power circuits
In many countries using IEC rules the phase conductors are brown (L1), black (L2) and grey (L3), the neutral is blue and the protective earth is green-yellow. Older installations and some countries use different colours, so always check the local regulations and the drawing.
Green-yellow is only ever used for protective earth. Blue is reserved for neutral in power circuits.
Control and DC wiring
Control circuits often use a separate colour, for example red for AC control and dark blue for DC control, so a technician can see at a glance which wires carry control signals. Panel builders follow the customer specification for this.
Wire size follows the protective device and the load; control wiring is commonly smaller than power wiring.
Wire numbers and ferrules
Every conductor in a professional panel carries a ferrule or marker at both ends with its wire number. The rule is simple: all wires at the same potential carry the same number, and the number changes every time the circuit passes through a contact, coil or device.
Good numbering lets you follow a circuit from the drawing to the panel and back. During troubleshooting you can say “I have 230 V on wire 3 but not on wire 4”, which immediately tells you the open contact sits between them.
Drawings and terminal strips
The schematic shows the wire numbers, the panel layout shows where devices are mounted, and the terminal strip drawing shows every outgoing cable. Keep all three up to date after changes. PlantFlow can export the wiring schedule to Excel.
Try it yourself
Turn on “Wire numbers” in the 2D diagram or the Wiring tab. Every tag shows its equipotential number, and the Excel export lists the full wiring schedule.
Open the PlantFlow 3D simulator →Safety: this guide explains principles for learning. Real installations must follow the applicable codes, the equipment manufacturer's instructions and the approval of a competent, qualified person. Isolate, lock off and prove dead before touching any circuit.