Color-coding wires powered by UPS

[wireman]

This is not an NEC question as I realize its color-coding concerns are limited.

But consider an industrial situation where the specs say that 102vac control wires shall be red and yellow shall be the color all wires from a foreign source or that will still be powered up if the main power to the control panel is turned off.

Many small PLC control panels are powered by a UPS so if main power is lost the processor and control wires are still hot. So the question is: should all of these wires in the panel be yellow?

 

[Smart $]

TTBOMK, no.

Yellow is for conductors whose power originates in/from other powered equipment, and not those wihich are powered from within the the control panel in question.

Because you have two power sources to the control panel (assuming the UPS is external), it should be labeled as having more than one power source and identify the disconnecting means for those power sources, or perhaps reference orderly shutdown documentation.

 

[wireman]

I couldn't find this to put in my original post but it's from UL-508A:
"Yellow ? ungrounded control circuits or other wiring, such as for cabinet lighting, that remain energized when the main disconnect is in the 'off' position."

So according to this it doesn't mean "foreign" supplies.

 

[tkb]

I don't get this.

If the wires that originate at another source in a control panel are suppose to be yellow, aren't they yellow at the source panel also?

So you could have yellow wires coming into a control panel as a remote source and yellow wires leaving the panel as a remote source for the other control panel or another control panel.

We used to use red for AC and blue for DC for all control wiring between control panels.

 

[jim dungar]

Typically the wires are landed at terminal blocks just as they leave the source cabinet; this is where they change colors.

 

[Smart $]

I couldn't find this to put in my original post but it's from UL-508A:
"Yellow – ungrounded control circuits or other wiring, such as for cabinet lighting, that remain energized when the main disconnect is in the 'off' position."

So according to this it doesn't mean "foreign" supplies.

If power is not "cut" to these wires when the main disconnect is opened, then they do not get power from within the cabinet, or are somehow tapped into the line side of the feeder. The only other possibility is more than one power source... and by more than one power source, I mean more than one feeder... not any control wiring which receives its power from other equipment fed from same power source but having separate ocpd and main disconnect.


I don't have the complete text of UL 508A, but does it have any provisions for wiring from more than one power source?