Wiring through attic

Question

I want to run a new 240V eletrical line to the garage as in the picture below. The dark blue one is the panel and the light blue is the garage. The problem is the roof is very sloped so it is almost impossible to get to that corner through the attic. I do have a hole going up from the panel to the house, but how could I fish something from that corner? do I have to open an area of ceiling from inside to do so? I really don't want to patch drywall (and painting)..

There is also an existing conduit that carries a 240V from the panel to the kitchen. It's about 1" in diameter. It does have space to have another 8/3 wire, so one option is to somehow break the conduit in the attic, and separate the two lines with a junction box. Is this something safe?

Alternatively, I considered to let the wire:

1. Go through crawlspace
2. Go directly through outside
3. Enter the attic from a vent, which is not far from the panel

They may work...but I still prefer to have it go through attic directly if possible. Any suggestions would be appreciated. Thanks!

Edit: I measure the conduit using caliper - the OD reads 1 7/32. It's plastic. There are 3 wires in it - 2x hot 8 TW, 1 neutral 10 TW, no grounding)

Answer 1

Easy peasy. This is what conduit is for.

I propose putting 2 circuits in it. However, there are strict rules on conduit fill, and putting 2 cables in a conduit is impossible to do legally. So don't even try - switch to THHN individual wires. Now you have plenty of room.

Yes, you'll need to find an appropriate point to install a junction box. Now, if you do any splicing in this junction box, any at all, you'll need to do the cubic inch math. However if all wires simply pass through the box, and never will be spliced, then you can treat it same as a conduit body and any common box with enough physical space will suffice. I'm a big fan of that one, so I advise running 2 separate ground wires - one for the range circuit and one for the garage circuit. That way you don't have to splice in the box.

If I wasn't splicing, I'd use a 4-11/16" square deep box. This box must remain accessible, it can't be mudded or plywooded over.

The oven circuit needs a #10 ground wire. It really should have been put in at the time, and you'll have a chance to fix that now. Its neutral also needs to be #8.

I know you're familiar with 8/3 cable, but you cannot use 2 cables in a conduit - the only way it works is individual THHN wires. You're not obliged to use conduit all the way - you can transition to 8/3 cable at any junction box with enough cubic inches to handle the splice. But if you do run conduit all the way, you get to run a higher ampacity: #10=35A #8=50A #6=70A.

---

The range needs a #10 ground (use bare to save conduit fill) and the garage circuit needs a #10 also.

The #8/#8/#10/none wiring to the range was (well, is) incorrect. It needs to be #8/#8/#8/#10. Further, if somehow it is cable, it needs to be switched to THHN wire because of the conduit fill problem.

Even if they are individual THHN wires, you need to pull them out of the conduit. You cannot modify the piping with the wire in it. Code prohibits this, and you'll nick the wire - trust me. Put the range circuit back with a #8 neutral and #10 ground. I don't care if you convert your range connection to 4-wire (removing ground jumper) today, but I hope you do it soon.

I've run the numbers and the biggest you can do is - a #8 circuit to the range and a #6 circuit to the garage - #8 circuits to both range and garage, with space left over in the pipe for up to 2 additional circuits!

A #6 cable to the garage could carry up to 70 amps if the whole run is THHN in conduit. If you switch to cable for part of it, then you're limited to only 60A. A #8 cable is similarly limited - 50A THHN-in-conduit, 40A if any cable is involved.

Or you could go with a big subpanel! You could potentially pull three #3 copper THHN wires (#8 ground) to the garage, and fit a subpanel there. The #3 copper wire would allow a 100A subpanel. That would fill the pipe, however you wouldn't have room for any more wires. You would then have to double back from the subpanel to serve the range.

---

---

* If you can't avoid a splice in a box, here are the gory details on the cubic inch math: Each #6 wire needs 5.0 cubic inches. Each #8 needs 3.0. Each #10 needs 2.5, #12 needs 2.25 cubic inches. One #10 ground can be shared among all circuits. For cubic inches, you only count the largest ground once, and all other grounds are "free".

Answer 2

I did something similar in my house recently, in a similar situation. The feed up from the panel on the outside of the house came up inside a soffitt, which had to come up a few inches before it even cleared the top plate. It would have been impossible to reach in there even if I did have a small child I hated enough to ask to do the job.

So what we did was: My wife stuck a coat hanger, I mean fish wire, up from the exterior, and I crawled as close as I could possibly get into the eave area, and stuck another fish wire over to meet her fish wire. Each wire had a hook, and her wire had a line taped to the wire. I was able to hook her wire, pull the string up, and use that to pull a sturdy rope afterwards. Once you have the rope in place, you can pull a cable through if one person pushes while the other pulls.

We did not feel that conduit was necessary as we were pulling 3 or 4 gauge service cable, which in my limited understanding is OK to run through attic space unprotected. If there is a code violation there, I hope someone will speak up.

I guess in your situation the difficult part would be to get a hole up inside the wall, behind the panel. You could run exterior (through properly sized conduit) into the eave/soffitt if that wasn't possible.

Answer 3

You want to stay away from doing anything with the conduit. I had a similar problem where I actually put in a few small sheets of plywood and crawled on my belly like a reptile and got back into that corner. If you can do that, you might just find enough space where the conduit comes through the ceiling to shove the 8/3 romex through and down to the panel. Then from the front or inside of the panel try to guide the romex into the panel.

If you have to cut the ceiling, use a hack saw because it will make a very thin cut. Cut a six inch square, do your fishing and then reattach the drywall cutout with a few furring strips and finish with joint compound.