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AssuredElectrical, Master Electrician
Category: Electrical
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Experience:  Contractor-42+ Years in the ElectricalTrade
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Can ac and dc voltage be ran in the same festoon cable?

Customer Question

can ac and dc voltage be ran in the same festoon cable?
Submitted: 1 year ago.
Category: Electrical
Expert:  Phil replied 1 year ago.

Hello, its never a good idea, the AC voltage can induce current in the DC wire... if the DC is used for signal transmission it can be negatively affected by the AC, the higher voltage and heavier amperage the AC, the greater the potential for problems.

Any DC signaling wire should be run in shielded cable as well.


If you appreciate my input so far, and wish to continue with virtually no time limit, rate my work positively... we can go from there. The company only pays me if you rate positively, lacking that I can spend days with a customer at my own expense, without any compensation. Rating does not increase your charges or close the question.


Expert:  Phil replied 1 year ago.

some codes, relative to fire alarm system wiring mandate keeping any signal wires separate from AC line voltage wiring for example.

Customer: replied 1 year ago.
the dc is running a magnet and the ac is running a trolley motor does the code permitt this
Expert:  Phil replied 1 year ago.

I believe that you can run the AC and DC in the same cable in that application but do not know for sure and have not found any code on it one way or the other. Much of the code relys on a manufacturers design and recommendations, if for instance you had a pendant with both AC motor controls and DC magnet controls on it and a manufacturers spec on what cable to use with his pendant, most inspectors would approve it, on that basis.

Lacking that specific cable specification, it seems that heavy amperage DC current for the magnet would act to magnetically distort the AC motor supply and would not be a good idea at all.


I am am not prepared on this end to dig into the issue any deeper, so will opt out, do not consider this an answer or rate it as such.

Expert:  AssuredElectrical replied 1 year ago.

Welcome. My name is ***** ***** would be glad to assist.

I see no reason why you cannot make the installation based on the information.

The Festoon cable with be one type with the same insulation on all conductors. We always had ours with AC motors and DC brakes in some applications.

This is based on the following in the code:

300.3 Conductors

(C) Conductors of Different Systems.
(1) 600 Volts, Nominal, or Less. Conductors of ac and dc
circuits, rated 600 volts, nominal, or less, shall be permitted
to occupy the same equipment wiring enclosure, cable, or
raceway. All conductors shall have an insulation rating equal
to at least the maximum circuit voltage applied to any conductor

within the enclosure, cable, or raceway


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