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Previous owner left a chunk of 3 line triplex(2 insulated + ground) 4 ga aluminum into the main panel, hooked it up to a 50A breaker, and left the other end floating free in the rafter space of our breezeway. I think this was eventually going to cross the breezeway and be wired to a sub panel in the garage.

The wire leaves the panel box through the bottom, and is secured there with what I'm calling a lock ring -- a threaded ring with angled teeth that is easy to tighten, but requires a substantial tap to free. The lock ring is on some threaded end that looks like the threaded end of a conduit connector, but I've seen similar looking strain relief devices.

In the breezeway, the wire comes out of the wall midway through the floor joist running on top of the wall. There is no evidence of conduit at this end. The wire comes out of a hole barely big enough for the wire,

So between these two points the cable makes a 180 degree turn passes through the stud supporting the north side of the panel box, heads up, and not quite sure how it gets from the wall cavity into the ceiling joist space then out through the joists into the breezeway rafter space. At least 270 degrees of turn.

I want to replace this triplex with 3 conductor (plus ground) 6 ga wire for a sub panel. Ideally I want to do this without taking the wall and ceiling apart.

A: Some form of strain relief/edge protection is required where the wire passes through the panel wall. If this is in place then that dingus with the threads is locked to the triplex cable. This will make passing the old cable out difficult. How do you remove something that originally came in from the outside, when you only have access to the inside?

B: I'm missing a bunch of vocabulary for the mechanical bits for doing this. Where are good sources that explain the mechanical bits by function: E.g. there are various strain relief devices.

C: Where can I find methods for dealing with getting fat wires through walls?

D: Is this one of those problems that can't be done by an amateur or without half a truck of special tools?

Additional information. Cables are secured at the box with a (surprise!) cable clamp. From the inside these are indistinguishable from a conduit end. Given the lack of any other conduit wiring in the house, this cable clamp is my working hypothesis.

Closer measure shows that the triplex goes through the stud on the north side, then straight up through the cavity space to the joist. House is 2x6 construction. This would leave room for the old path to be beside the end joist.

I've determined that the 2nd floor joists run east/west. The joist in the breezeway is the header joist/end joist, so is likely 1 wide, not doubled.

So at this point I've got two options:

Option 1:

  • Cut the old cable off on the inside of the panel box and it's exit into the rafter space, abandoning it inside the wall

  • Drill a new hole in the joist at a slope that will also take it through the wall header (Could also go through just below the joist

  • Use another knock out on the north side of the panel box. Drill through the stud through the knockout hole. Verify that I'm using the right size knockout for 6/3 wire.

  • get whatever people use for old work cable clamps that can be installed from inside the box. (What are they called?)

  • Initially run an elongated loop of bailing wire tied to a 1/8" nylon line into the hole from the panel end.

  • See if I can catch that loop from the breezeway end with a fish tape. (The issue with this: This is an insulated wall cavity. Tips on fishing?

  • Pull the line through.

  • Secure the other end of the line to the end of my 6/3 AWG. Create an end for it using a buildup of duct tape so that it has a taper that is less likely to catch.

Option 2

  • In the corner of the upstairs room that is over the stud space next to the panel, peel back the carpet Cut though the 1/2" porridge board underlay, and the 5/8" plywood subfloor, hopefully seeing the top of the wall. This makes the fishing easier, but means I have to put back the floor. Overall I think this is easier than repairing and painting the wall. Do have to move two bookcases to get at the corner however.
  • A couple of pictures would be really helpful. – jwh20 Jul 13 at 21:37
  • Is the existing wire actually a cable? If so, can you get pictures of the outside of the cable - there are usually codes on it which will indicate what type of cable it is. Depending on the type, you may be able to use this cable instead of running a new cable. – manassehkatz Jul 14 at 2:15
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    You may have asked and answered this elsewhere... but can you live with 120V in the garage (and a fair lot of it)? Alternately, can you use 240V-only in the garage plus 1 or 2 120V circuits? Also you are totally allowed to use #4 4/3+gnd aluminum, price it both ways... at these sizes, aluminum doesn't bite, but it is quite a bit harder to bend. – Harper Jul 14 at 21:22
  • Yes I did. I need 220v at ~20A for a table saw. + 110v for lights, garage door opener, outlets for non-stationary tools. In theory I can run an individual wire, but using triplex between panel and sub panel will raise eyebrows when the house is next inspected. Not clear that running a single wire would be any easier than replacing the whole line. From the panel to the sub panel is under 20 feet. – Sherwood Botsford Jul 14 at 23:56
  • @manassehkatz The markings are really hard to read. It's 3 conductor -- 2 insulated, one steel stranded ground. Which means I need a 4th conductor to have both 220 and 110 in the garage. (Right now the garage runs on an extension cord and a power bar.... <rueful grin> – Sherwood Botsford Jul 14 at 23:59

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