If you are asking if it is an NEC violation, the answer is probably no. The exception would be power-limited circuits covered under Article 725. All conductors in the duct must be insulated for the highest voltage level carried by any conductor in the same duct. In general, the NEC allows voltage levels to be mixed - up to 1000 V.
However, that fact that it is allowed under the NEC does not mean that there could not be some noise-related issues.
The different voltages are not really the issue. Like dpc said, within certain limits, different voltage cables can be mixed. However, the NEC does require the separation of power cables and instrumentation/communication cables. I think this is more of an AC problem, since AC power cables can produce noise on adjacent cables. I personally don't expect DC wires to produce any noise in adjacent wires.
In the NEC, Article 800 (for communication cables) and Article 725 (for signalling cable) both state that power cables and other cables can be installed in the same raceway as long as they are separated by a barrier. For example, I just had some 12" wide fiberglass cable tray installed. It is separated into an 8" wide section and a 4" wide section by a fiberglass barrier. That way, I can run power cables in the 8" section and instrumentation cables in the 4" section.
Thanks so far for all the input. Keep them coming. I knew of the not mixing very high ac volt with low and also mixing of ac & dc. But when it is 100v DC difference is what propmpted me to ask the question.
The configuration is that I have a AB Flex I/O. The Control net adapter is powered by 24vdc. The rest of the input modules are 125vdc. I have one duct running down the connect side of the devices which would require me to put that 24vdc Controlnet power and the 125vdc inputs in the same duct.
