Yellow wires for foreign power


Thread Starter


It is known that all wires that do not get disconnected from the main disconnect of a certain
enclosure panel shall be yellow?

Does this apply to 24VDC foreign power as well? Or is there an exception.

Thank you

Bouchard, James \[CPCCA\]

It is a common practice but it is not required by all codes. I have also heard that some countries use orange for this.

James Bouchard
I haven't seen any spec. that differentiates AC from DC with respect to colors for those wires powered by an external source (i.e. that may be still powered when the local disconnect is off). I've adopted the practice of using yellow with a blue stripe for low voltage DC signals or power, and yellow with a white stripe for either DC or AC commons where that common is tied to ground outside the realm of the local disconnect.

This has met with a positive reception wherever I've applied it - typically within the auto industry.

A little off the subject, but also be aware for equipment subject to IEC requirements, the wire color for this type of interlocking is orange rather than yellow. Since virtually everything in europe is 24 Vdc, I just use solid orange, rather than stripes. Striped wire that satisfies the European harmonized specs. seems to be very difficult to get hold of.

Jim Mooney

Steve Myres, PE

That's just the point. Many times the foreign wires are of unknown or unspecified voltage (or the voltage may be changed at some future point). For example, your machine may be providing a dry contact for wiring some interlock. The voltage supplied by the signal consuming equipment may be 120 or 240 volts for all you know.

One thing I've done when a machine has a large number of foreign voltage interlocks, is to build a separate cabinet specifically for the interlocking relays. Then, when you are in the main machine control cabinet where most of the troubleshooting is done, you needn't worry about the presence of foreign power.