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Preface: I dont want to repeat the question already posed here.
I am a reasonably smart individual that does work around his house. I graduated with an EE degree way back when, so concepts of electricity are not foreign to me. I am aware of many of the reasons why one should not run Ethernet cable parallel to standard house power cable (magnetic induction causing interference, potential safety issues if both cables are punctured, code violations, etc).

All that being said, I am still asking this question and I wont hold it against you if you call me an idiot. :)

Situation: I am installing a Foscam weatherproof web cam just outside my garage. The camera supports PoE and I have a PoE router that it will connect to. I plan to connect the router and webcam using cat6 Ethernet cable

There just happens to be a motion sensor light just outside my garage. The motion sensor light consists of an junction box (exterior) and some Sch. 40 conduit that goes thru the exterior wall into the garage interior. This conduit leads to another junction box (interior) where power is routed from the house. The total wire distance between interior and exterior junction boxes is about 2 feet.

I want to avoid drilling more holes in my house. I am considering running my cat6 cabling between the junction boxes (thru the conduit) and having it exit the exterior junction box. I would then hook it up to my webcam mounted close by. The Ethernet would only be parallel to the power cable for 2 feet of length (even though the actual Ethernet run would be much longer). Also the Ethernet would be within junction boxes and conduit the whole time it is together (increasing safety from random nails and such).

Question: Im reasonably certain that there is enough shielding in the power and Ethernet cables to avoid a short between the two. However I am wondering how worried I should be about 2 feet of parallel run? Is that enough distance to have adverse effects? Also, if there is a constant inductance, how worried should I be about my PoE router and webcam being damaged over time?

Any and all speculation and empirical data is accepted. :)

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    Poke a fish-wire through the wall alongside the conduit, the pull the cat6 cable through. Add some caulking then replace the 2 junction boxes.
    – John Canon
    Jan 29, 2019 at 2:28

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Sorry, but I don't think you are allowed to do this. See Cat 5/6 in same conduit as power: is NM-B required, or is THHN acceptable? for more information.

So while there may or may not be any actual technical problem, there is a code problem. Would there be a problem running your Ethernet outside the conduit, just inches away? According to code, no problem at all (as far as I know). Would it cause any technical (signal quality) problems? My guess is probably not, especially for just a few feet.

But you can't run it inside the same conduit. You can (and this is a frequent suggestion when pouring concrete or digging a trench) run multiple conduits and have a small one for network/phone/etc. and a large one for power. But you can't just throw everything into one conduit.

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    Thanks, accepting this answer (even though Harpers also has good suggestions). For completeness sake, I ended up just drilling a small hole thru my stucco and drywall for the ethernet cable. It can be easily repaired/painted later if needed.
    – Martin M.
    Feb 5, 2019 at 23:32
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Can't do it. You cannot mix Mains and Data wiring in the same raceway, cable or conduit, and the reason is safety not line noise.

What you can do is convert the outdoor LED motion sensor to 12V or 24V, and supply that from a power supply below the point where the ethernet joins the conduit. Low voltage circuits below 55 watts are classified similar to data cables. (can mix with data cables, can't mix with mains).

There is one exception to the "no data" rule, and that is, obviously, fiber-optic which contains nothing metallic.

There is one last exception but it's useless to you: if the low voltage electrical system is entirely contained inside Class I wiring methods, that is ok. However that means you can't do things like bring the Ethernet to a wall plate and send it on into a PC, because that would be part of the circuit yet escaping Class I wiring. It is used for things like lighting or SCADA power controls in commercial buildings.

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  • +1 for brilliant idea of converting all the conductors to harmless voltages.
    – A. I. Breveleri
    Jan 29, 2019 at 5:03
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    @A.I.Breveleri It is the combination of low voltage & limited current that makes it relatively harmless. 12 V full current (cranking amps) out of a car battery is pretty dangerous. At lower current for a couple of LED fixtures, no big deal.
    – manassehkatz-Moving 2 Codidact
    Jan 29, 2019 at 5:08
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As indicated above, you can run the UTP near the conduit, but you cannot run it in the same conduit as the power cable. Additionally, you must support the UTP on its own; you cannot support it from the conduit. UTP is pretty small. I would just drill a small hole in the wall, run the cable through it, install the RJ-45 and caulk the hole. If you decide to remove it, you can easily fill the hole (a bit harder if you have metal siding but still not impossible) and paint it. You'll never know it's there.

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if by shielding you mean metallic shielding, there is none at all on UTP and on the power lines to keep the RFI/EMI from getting out

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