Then wiring in my house is old, much of it cloth wiring. The electrical cabling goes from an outdoor main panel down a conduit into the ground and comes out in the crawlspace. I'm wanting to rewire a good portion of my house with new wiring and reroute it through the attic. Is the best approach to run conduit through an exterior wall from the crawlspace to the attic? I'm thinking of using thhn wire. It's all 12 AWG wiring. How much can I run through one such conduit? There a better way to do all of this? Thanks.

Addendum: There really isn't any existing conduit. Some of the wires run through this rubber conduit toward the center of the home, and some wire runs exposed to different parts.

When you say to terminate the wires into a junction box, are you talking about a pull box? How can one terminate 10+ circuits into a junction box?

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    How hot does the attic get? Are you in the sun-baked southwest (Arizona, southeast California, Central Valley, New Mexico etc.?) Jan 28, 2023 at 22:05

1 Answer 1


You can run 16 #12AWG in 3/4" EMT conduit and 26 #12AWG in 1" EMT conduit. You didn't mention what size conduit you have. You might want to utilize the existing conduit and THHN from the panel to the crawl space and have a large junction box there and branch off to different areas with NM cable if your house doesn't have conduit. Run an additional conduit from the panel up into the attic. Add a large junction box and from there, branch off with conduit or NM cable. All THHN needs to be in conduit, NM cable does not. Some areas do not allow NM cable.

  • If you run more than ~ 3 circuits in one conduit longer than 24", you run into derate rules that make it more cost effective (because of larger wire cost) to use multiple conduits. Jan 29, 2023 at 0:28

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