Electronic – How to properly label power wires

powerwiring

Basic and stupid question, however it bugs people and creates misunderstanding.

I frequently see the following labeling of 3 wires in the cable

  • wire 1: "+24 V"
  • wire 2: "-24 V"
  • wire 3: "ground" or ground electrical symbol (without circle around it).

When I ask people what is the supply voltage, they say: 24V. When I tell them that according to their labeling it must be 48V with central ground. None still have shown me wire 3 being marked "PE" (then it will be clear that it is not a signal ground, and things are not that they appear to be).

Thus what is the correct way to label 3-wire cable so that everyone understands immediately that power voltage is 24VDC?

I think it must be GND, +24V and PE. Is it correct or there're any other ways? What if power supply must be isolated? If power is AC?

Best Answer

For industrial applications:

  • PE for protective earth. Green / yellow for wiring.
  • 0V for 24 V supply common is generally good because its meaning is clear. White with blue stripe is normal in Europe.
  • +24V is usually split by fuses, circuit breakers or electronic fault protection units so additional wire numbering is required. +24-1, +24-2, etc., would make it very clear. Blue wiring is common in Europe.

If the power must be isolated I would be inclined then the argument could be made for 24V+ and 24V- (with signs after the voltage) . This should still be adequately clear and does not imply a ±24 V power system.

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