Is there a Control Cabinet Wiring Code?

Noticed the following Facebook post which we wanted to share. At Rom-Control, we specialise in repairing your electronic control systems from all types of industries and we have seen different coloured wires connected to similar systems. To an untrained eye, there doesnt appear to be s system or standard but that is not necessarily true.

The question on Facebook from the electrician who recently entered the industrial workforce was …….sometimes I see control panels with wires in different colours (orange, white, black, grey, purple, yellow, red…). I know they are used for control systems(PLC, sensors…) but I don’t know which colour is used for which circuit. Is there a standard for which colour is supposed to be used?

The answers were varied and interesting as shown here but does anyone know the real answer?

Answer 1. Every company *could* have a different standard. Most panel shops stick to the NEC standard. The multi meter won’t lie to you.

Answer 2. Orange is coming from outside the current panel. White is neutral, white with blue stripe is com. Red is 120V control power inside the panel, black is providing 120V power, usually to receptacles or circuit breakers. Blue is 24V. That’s the standard everyone should use.

And from the person that built the panel as shown above in the picture – “actually, I built this control panel 2 yeas ago”. The engineer that planned it doesn’t know why he used that color coding, his comment was “this is how they teach in electrical engineering school so it is what I did”.

The real answer is found in AS3000:2018 Section 3.8 which specifies that “internal wiring of equipment is not regarded as installation wiring” but certain rules must be observed with certain wiring insulator colours. It is worth a read if you have involvement of wiring up any switchboard or control system cabinet to ensure you conform.

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