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I need to make a run from my detached garage to my house. The run exits the garage by way of an LB, runs underground for 25ft in 1 1/4" Schedule 40, then enters the house through another LB.

From there, the panel is another, 40-50ft? It needs to jog up a wall, run parallel along a joist, then it needs to jog back down into the basement. I'll need to drill through several basement joists that are perpendicular to get to to the main.

Originally I had planned to run 6-3 copper wire, but based on my previous post... https://diy.stackexchange.com/users/login?ssrc=head&returnurl=https%3a%2f%2fdiy.stackexchange.com%2f%3ftags%3delectrical

It's clear that running individual wires in the conduit will make more sense and perhaps using aluminum as well - I am fine with either/or.

Questions:

  1. Should I plan to run the individual conductors all the way from the sub-panel to the main without stopping? If so, what wire types could I use for that?

  2. If I don't use individual wires the entire way, what should I do? e.g. Terminate at both ends of the conduit in a junction box and switch to a different type of wire? But junction boxes can't be buried in a ceiling or wall - so that doesn't sound right either...

I'm honestly fine with running individual wires the entire length if that makes the most sense - it just raised my "spidey sense" that there might be a better way to do accomplish this...

Layout Diagram

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    Is there any reason you don't want to run conduit the whole way?
    – ThreePhaseEel
    May 21 at 1:27
  • It would just be a real pain in the ass. I'd need to get really clever about how to make the PVC bend in a way that I can properly seal back up the walls, plus I need to drill through about 6 joists....I'm not even sure how I'd get the PVC up in the joist bays (16" on centre) without making a bunch of short cuts and then gluing it all back together.
    – Ray
    May 21 at 20:24
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    Do keep in mind that you can transition from PVC to ENT (smurf tube) for the indoor run
    – ThreePhaseEel
    May 21 at 21:01

2 Answers 2

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It’s always better to run unspliced wires end to end. If you are in a position where you can use conduit connected to both panels without breaks and pull individual wires through, I would say that’s the best choice. It allows you to pull new wires easily in the future if you decide to increase the amps available in the garage.

In terms of type of wire, it really depends on what you’re doing. Sounds like you’re connecting a main panel and sub-panel together. What is the planned ampacity for the sub panel? Generally this is a good use case for aluminum wire. I personally would choose wire with XLPE insulation, which in the US is usually sold as XHHW or USE wire.

That’s what I’d do.

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  • Plan was to put a 60AMP breaker on the main for this run. I understand using aluminum of a slightly large gauge might allow for up to 90 AMPs and still fit the 1 1/4" conduit. Just wasn't sure what wire type was appropriate to run this both underground AND also inside the house.
    – Ray
    May 20 at 23:38
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    @Ray as long as the conduit continues underground the entire length, aluminum wire rated for wet locations are fine. XHHW-2 being a good option.
    – RibaldEddie
    May 21 at 0:35
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    @Ray and the XHHW-2 wire can also continue the entire run of conduit above ground too, just to be clear. You can have the conduit terminate directly in the panels through a knockout, secured with threaded PVC fittings, metal locknuts, and plastic bushings.
    – RibaldEddie
    May 21 at 0:40
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Well, the lugs on the panel are made of aluminum. Which undercuts most people's reason to consider copper.

Couplers are costly, so it's better if you can avoid them. However, it's difficult to find aluminum cable that is legal both underground and also in walls without use of conduit. Canada has a special cable type called TECK, which is similar to MC cable with an outer rubber jacket. NEC didn't write a new article just for Teck, they modified the MC cable rules to allow "MC cable if listed for use underground/outdoors".

But the other option is to simply run conduit the whole way. You need to build the conduit complete before pulling any wires. There need to be access points sufficient so that there aren't more than 360 degrees of bend in the conduit in between access points, and those must remain accessible forever without tearing apart the building. LB's count as access points.

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    Encore has started making dual-rated TC-ER/SER cable that's also legal for a single pull in a mixed indoor/direct-bury situation BTW
    – ThreePhaseEel
    May 21 at 1:27
  • A complete conduit run would be a real pain I think. The basement joists are perpendicular to where the conduit would need to run, so I think I'd have to cut the conduit to fit, then drill holes, insert the short sections and glue it all back together. That's assuming I can meet the 360 requirement, which Im not convinced is doable....what about terminating at the LB attached to the house? Ive read that if the LB has a size stamped on it, this might be a legal way to allow me to terminate and then run a different and simpler to install wire inside the house...thoughts?
    – Ray
    May 21 at 20:27

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