Marking of different raceways

[Alphabet]

Is there any standard or requirement for marking raceways of different systems? For example we use flex conduit for both 600-120V AC and 24 V DC applications. An inspector is questioning why there is no ground or bond conductor in every raceway. Based on the following ref, we do not need to install a bonding/ground conductor in the DC raceway:

10-102 Two-wire direct-current systems

(1) Two-wire direct-current systems supplying interior wiring and operating at not more than 300 V or not less
than 50 V between conductors shall be grounded, unless such systems are used for supplying industrial
equipment in limited areas and the circuit is equipped with a ground detector.
(2) If such a circuit operates at more than 300 V between conductors and a neutral point can be established
so that the maximum difference of voltage between the neutral point and any other point on the system
does not exceed 300 V, the neutral shall be permitted to be grounded.

We are less than 50V so the following would come into play.

10-114 Circuits of less than 50 V

Circuits of less than 50 V shall be grounded

1. where run overhead outside of buildings; or
2. where supplied by transformers energized from

• (i) systems of more than 150 volts-to-ground; or

(ii) ungrounded systems, unless the circuits are provided in accordance with Rule 10-112.

We are not supplied by transformers over 150 VTG so this does not apply as well.
The systems are in different raceway configurations.
So the question remains, is there an acceptable way to mark the DC raceway as such to help the inspector determine what is AC and what is DC?

 

[LarryFine]

I can see marking at J-boxes and other access points, but I see no need to mark raceways.

 

[Coppersmith]

I wired a school that required that the pipes be color-coded (fully painted) by what they were for. When we were done, there was six different color pipes.

 

[Jerramundi]

Not code requirement as far as I'm aware, but it can be spec'd that way.

As @Coppersmith said, there are conduits available of different colors for different purposes... but that color system isn't governed by any national standards... except Red Conduit for Fire Systems. I think that may be nationally mandated, I'm not sure.

The other colored conduits have non-binding industry standards, but are really up for grabs. Talk to a few guys and you'll find their uses varying throughout the country.

Me personally, and I know some will laugh at this, I mark my conduits containing the ground system with a single wrap of green electrical tape about an inch from every junction point. A little over the top, but I like it Ultimately, without a nation wide, binding, industry standard to let the next guy know what that color system or labeling system means, it's really just a design choice.

 

[Jerramundi]

There's no rule AGAINST affixing a label to the conduit and/or painting it... so you could put a printed label on it and/or make something like a "12-24 VDC" cookie cutter out of paper and spray paint the words on the conduit if you like... but there's no legally binding industry standard for what you are asking as far as I'm aware.

Most of the time low-voltage isn't in a conduit raceway and people use the required text printed on the wire itself to discern the difference.