What precautions or steps are needed when routing Schedule 40 PVC Electrical conduit across (90 degree crossing) a lightning prevention downlead? This downlead looks to be braided copper cable approximately 1/2" in diameter. Is there a specified distance between the PVC conduit and the downlead? For your consideration, I live in Philadelphia and I'm looking to install security lighting on a 20 amp circuit running on 12 gauge THHN.

1 Answer 1


Of all the homes I help oversee the construction of, the main thing that was followed when it comes to lightning protection is no sharp bends in the cable, or uphill runs. Always going down to ground. It can be run through walls, by means of drilled holes through the plates, so a close proximity of a non conductive PVC will be no problem. If you want to be safe, get a small gap between the conduit and the cable, though I think it does not need to be much say 1/2"to an 1". Since static electricity carries over the surface of the wire and not through the wire, which is the reason the cable is loosely braided, a little space between the two should suffice, just to be sure.

  • Is interference and/or current induction in nearby conductors not an issue at all, here? Commented Jan 18, 2015 at 6:31
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    The only time when that type of interference would be a problem is when installing low voltage systems. Data, speaker wiring, and the like will pick up interference in line voltage wires that are traveling to close. The OP is only installing security lighting, not communication, so I would expect the line load to be 120V or similar, not falling into the low voltage category. In addition, the cable he refers to is only going to be "live" when there is a lightning strike, Then there may be some "atmospheric bleeding" I believe that is part of the function of a lightning rod too.
    – Jack
    Commented Jan 18, 2015 at 23:20
  • Once upon a time in college, which was a year or two (or 25) ago, I was the first one of all my roommates into a new apartment. I picked the room I wanted, moved my stuff in, set my computer up on the desk, turned it on, and the image on my expensive CRT monitor was waving around like crazy. So I ran around the back of the building and sure enough, the big conduit bringing power into the building run right past my window. I moved into another room and everything was peachy, though I felt a little guilty about my two roommates sleeping with their heads in that EM field unawares. Commented Jan 19, 2015 at 1:41

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