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I'm trying to add smart light switches (I was thinking of Shelly 2.5) to my appartment, but the problem is my lightswitch enclosure doesn't have neutral wires. It just has a live wire that enters the lightswitch, exits and goes on to the lightbulb. The lightbulb has a neutral wire which completes the circuit. This is standard electrical wiring over here in Eastern Europe.

Current wiring

I'd like to run a new conductor from the junction box to my lightswitch 1-1.5m through an existing kopex tube with 3 existing conductors.

Question is what's the best way to do this?

I tried stuffing the conductor down the kopex tube but it got stuck after about 15 cm. The tube diameter is larger than the wires, but perhaps they've bent and twisted inside.

Would an electrical fishing rod work for adding the wire without removing the existing wires? Thanks!

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  • Pictures would be helpful, in part for terminology differences (I'm unclear if Kopex tube is similar to "non-metallic conduit" (or less formally "smurf tube" since most is blue for power wiring use, while orange is more typically low-voltage) or some other type of conduit. Looks like it might be a metallic flex conduit, perhaps with a plastic outer layer?
    – Ecnerwal
    Sep 5 '20 at 13:12
  • probably this stuff: new.abb.com/low-voltage/products/conduit-fittings/kopex-ex/…
    – Jasen
    Sep 5 '20 at 13:19
  • Have you considered adding smart light bulbs instead? One brand (of many) could be Philips Hue.
    – ghellquist
    Sep 6 '20 at 6:30
  • Use safe, approved products. China puts fake CE marks on everything, and direct mail bypasses your nation's safety controls, so everything mail-order (especially Amazon Marketplace) is dangerous junk unless it has a real testing lab's imprint like BSI or TUV. CE is only meaningful when you buy it from a reputable bricks-and-mortar shop inside the EU. Of course that costs more because unsafe is cheaper. Sep 6 '20 at 16:15
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Without knowing the details for the Kopex tube (though it looks like it's probably some sort of flex conduit from a quick search) The normal way to "add wires to conduit" unless it's a very short distance is to shut off the power to the affected circuit(s); disconnect the wires at one end; attach a rope; pull the wires out the other end; pulling the rope in, attach the new wire, and pull them all back in together.

While this appears (to the uninitiated) to be a lot more bother than "just adding a wire" there is no "just" to adding a wire unless it's a very short, preferably straight section of conduit.

If there's no wire in the conduit in the first place, pulling a string in with a vacuum or getting a fish tape through are typical ways to get started. My personal experience favors the vacuum.

Using a fish tape or rod in a conduit with wires in place risks damaging the insulation on those wires and generally gets all tangled up in them anyway.

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  • Thank you all for your answers. Indeed, kopex is a plastic corrugated tube. I feared it would mean removing the previous wires before adding a new one. I'll see how that goes...
    – Adrian
    Sep 6 '20 at 16:21
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Running a fish down the tube with existing wires is a bad idea because you can damage the insulation on the existing wires resulting in short circuiting the circuit. Your best bet is disconnect the wires at one end and fasten a fish, string, to the ends of all the wires. Then slowly pull the wires out from the other end. Then attach the neutral to the string, fish, and other wires and pull the wires back into the tub. This is really an easy procedure.

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