Low voltage and normal power in same raceway

[wc86]

Hello all electricians smarter than myself. Im trying to understand when "low voltage" like an 18/2 or even a Cat6 wire can be run with 120/277 wires in the same conduit if any. I really want to know where the line in the sand is and how things like luminaire dimming MC cable fits into the picture. Unless the answer is UL listed wire can break any rule it want lol. Im not necessarily speaking to a specific install. But the question did come up when doing a commercial kitchen hood with ansul/fire alarm/MAU/PCU controls. The common concensus was "dont do it". But can you ever in any scenario?

 

[don_resqcapt19]

Look at 300.3(C), but make sure you read the section referenced in the Informational Note. In general, the "low voltage" conductors or cables cannot be in the same raceway with power conductors.

The dimming conductors in the MC cable comply with 725.136(I). As far as I know there is no low voltage cable on the market that you can buy and install in the raceway with the power conductors.

Note that some of the dimming circuits are Class 1 remote control and signaling circuits, and if that is the case the conductors and/or cables for those circuits can be installed in a common raceway with the power circuit conductors as long as you meet the requirements of 300.3(C).

 

[cabledawg]

The Only thing that can run with High voltage/Power is Fiber(as long as its NON-Meltallic). To Answer your question, NO! Not under any circumstance/scenario. A 2nd rate installer does it to save time because their boss says "Get the job done" of else. Power can and will induce a hum/impedance on your cable that will cause it to fail. For Residential, I could see it on occasion if you fish the wall to hide the cables(HDMI/power/Co-ax/Speaker wire) for the customers brand new 75" TV that he wants mounted on the wall before SuperBowl. Even so....that would be an "Extreme Temporary measure" if you come back and do it properly later. Good Luck out there.

 

[augie47]

Many a mistake is made by folks who fail to adhere to the Information Note don references.
300.3(C) is fairly cut and dried; unfortunately the same can not be said about Art 725.
In general, the determining factor is based on the LV being a Class 1 or a Class 2 or 3 circuit and then checking on the limitations.
I have found two of the more common determining factors are the one don referenced (725.136) and Exception 2 to 725.130(A).