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I have an existing low-voltage old-work box similar to this which I am using to provide a cable TV outlet:

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I would like to run more cables to this location, namely, phone and CAT6. I do have access to the location behind the wall through the attic. However, I would like to improve this by drilling a hole through the floor into the basement where all the cables come into the house anyway, and pushing ENT through the hole and attaching it to something different in this location (this box does not have ENT connections).

enter image description here

The only way I know of to make this work is to rip out drywall to expose the entire cavity between the studs, install a new-work low-voltage box to one of the studs, and replace and patch the section of drywall:

enter image description here

I am certainly capable of doing this and have done similar tasks in the past, but would rather avoid the extra work if possible.

One thing I have done in other locations is to push ENT into the wall cavity and get it close enough to the outlet location that when I fish cable though, it is possible to grab it through the hole with fingers or pliers. However, this particular wall cavity has the chimney stack behind it with extra room (much deeper than a 2x4 stud cavity), so cables have too much room to wiggle around and there is a risk they will be too far behind the wall to reach and pull through the outlet box. If I can somehow do the difficult task of grabbing ENT once, and get it attached to a box, then future work will be trivially easy.

Is there a way to securely attach ENT to a box in this location without removing any drywall?

This particular project is restricted to low-voltage work and does not involve real electrical. Location is the USA with no known building codes out of the ordinary that are relevant to this project.

  • Are you drilling the hole in the floor from the basement side? – A. I. Breveleri Aug 4 '17 at 18:25
  • @A.I.Breveleri yes. I have access above and below the wall, although below is much more convenient. – user4302 Aug 4 '17 at 18:26
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Just use a metal old-work box, perfectly fine for low-voltage stuff. It will have standard knock-outs for conduit connection, as opposed to PVC boxes which commonly have spring-lever grabbers for NM sheathed cable:

enter image description here

  • Wouldn't that have to be grounded, though, even if there is no 125v wiring in the box? – user4302 Aug 4 '17 at 18:25
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    Doesn't matter. When doing low voltage you are not obliged to use low-voltage boxes only. You can also use wiring methods intended for line voltage. You cannot mix low-voltage and line-voltage wires in the same raceways or boxes (without partition), unless the entire low-voltage system is protected the same as line voltage. – Harper Aug 4 '17 at 20:19
  • I could not find an off-the-shelf old work box with 3/4" knockouts, but I was able to make my own. I took a plastic old work box, cut a hole for the ENT connector, and used my Dremel to cut the top and sides off the box. That way I can get RG6 in there, which is very stiff and cannot make the bend to fit in an enclosed box like this one without compromising its structural integrity. However, your idea was the closest, so you get the accepted answer. – user4302 Aug 5 '17 at 18:34
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  1. Drill the hole in the basement into the wall
  2. Push your ENT up to the opening after you remove the box.
  3. Put a connector on your ENT if you haven't already.
  4. Here is the trick, insert a bent piece of tie wire or a bent coat hanger into the ENT.
  5. Put you low voltage box over the wire and insert it into the wall.
  6. Pull on the wire to bring the connector up into the box.
  7. Once the connector is in the box pull hard on the wire to remove it.

Usually this trick works better with steel flex and a locknut but it can be done with ENT.

Good luck!

  • When you say "low voltage box" which box do you mean? The old-work boxes do not have ENT holes, the new-work boxes cannot fit through the opening in the drywall. – user4302 Aug 4 '17 at 20:12
  • Look at the old work box jimmy fix it posted there are knockouts. – Ed Beal Aug 4 '17 at 20:21
  • I can't find them at the moment but Menard's sells a black plastic box with KO's and screws inside the box. So you can insert it into a hole next to a stud and screw it to the stud. The key here is the hole has to be next to the stud though. Otherwise you have to use something more like JFI posted. – ArchonOSX Aug 4 '17 at 21:13
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I think you will find it much easier to push a fish tape through the hole than trying to fish the ENT directly.

It's probably going to be easier to push the fish tape through the hole from the outlet side, where you hit the hole by controlling the tape, rather than by pushing the tape up from the basement and trying to grab it inside the wall.

Either way, once you have the fish tape in place, you can either attach the end of the ENT in a traditional manner and pull it through, or slide the ENT over the end of the fish tape and push it through the hole using the stiff tape as a guide.

If you don't have a fish tape, you can try using just about any stiff wire or tubing. I have fished short distances such as you describe with a 10/2 romex, 75ohm coax, and the plastic tubing that delivers water to my refrigerator. The principle is to trace out the path with something stiffer and more controllable than ENT, Cat5E, etc.

  • I was thinking the same thing, using fish tape and put ENT around it and use it as a guide. ENT is fairly stiff and goes wherever it wants to go until it meets the sweet embrace of two-hole straps that say "no really, you will stay here until I say otherwise." – user4302 Aug 4 '17 at 18:43

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