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Im running power to my shop at a distance of 175 feet. I am running #1 copper in 1 1/2” conduit from the garage to the shop. I ran into a problem in the garage - there is a 40amp circuit running through the middle of the studs just below the main panel I am connecting to (I have two 200 amp main panels - the 40 amp circuit is coming from the other panel). The size and position of the 40 amp circuit does not leave enough room for the 1 1/2 inch conduit to finish its run to the panel behind the drywall - trying to penetrate the wall above the 40 amp circuit would be very difficult as there is not much room between the panel and the circuit. Can I terminate the conduit after it penetrates the wall into the garage and finish the run to the panel with the wires (no conduit) behind the drywall?

Thanks for the answers … I was going to run 4 THWN - 3 1AWG and a 6AWG ground in pvc underground. I will make the change to #1 aluminum. Sounds like terminate the 1 1/2” to a junction box just inside the wall, then continue with smaller conduit up to the panel?

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    Wires, or cable? Wires must be protected.
    – isherwood
    May 19, 2023 at 15:50
  • The answer might be different for different locals(maybe down to city). Some places require conduit and do not allow cable, other places conduit is just an option. Usually conduit type wires must be in conduit and not loose. If your local allows cable, then ending the conduit in a junction box and continuing with cable might be a choice.
    – crip659
    May 19, 2023 at 15:50
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    If you haven't bought the wire yet we have some advice for you...you're throwing a lot of perfectly good money away.
    – Ecnerwal
    May 19, 2023 at 15:51
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    How much power do you expect to actually use in the shop? 1 AWG copper will get you up to 130A. (75C). But my hunch is you're putting a 100A breaker on this circuit. In which case 3 AWG copper or, much less expensive 1 AWG aluminum will do the job just fine. Voltage drop should really not be an issue unless you expect to really max out the circuit at 240V (even then, not much of an issue) or are calculating based on 120V. Remember that EVSE, welders, HVAC, lots of "big" tools are either primarily or entirely 240V machines. You could easily use 50A - 60A @ 240V while using 30A or less May 19, 2023 at 18:13
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    @ 120V and that 30A 120V is equivalent to 15A @ 240V. Look at your loads, figure out real-world usage and then figure out the wire size & type. Big conduit is good - easier pull and room for expansion. But I suspect you don't actually need 1 AWG copper. May 19, 2023 at 18:14

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First and foremost, conduit installation requires the entire conduit be built complete before any wires are pulled in. Some novices think they're supposed to lay the wires on the route then slide conduit sticks down the wire one stick at a time; no, that's forbidden due to high chance of wire damage (especially due to PVC cement) and chance of building a route that is completely un-pull-able. It must be possible to pull in replacement wires. These rules don't apply for conduit used as a "stub-up" at the ends of a direct burial run.

However THHN or XHHW wire must be in proper conduit its entire route.

Possible errors complicating matters

One of the reasons you need such large conduit is that you chose such large wire. We see a lot of people installing subpanels, and we see 3 very common errors and 1 missed trick, 3 of which bear directly on why your conduit is so wide. To get the irrelevant one out of the way first, most novices think "copper" for heavy feeder because of linear thinking or irrelevant scary stories about aluminum. Aluminum heavy feeder is proven safe and what's more, the lugs it will be landing on are made of aluminum for good reason. Copper is costly and pointless unless you have a conduit size constraint, BTDT :)

Then there's panel sizing. I find the vast majority of askers here who spec 100A feeder "picked that number out of thin air"... and it doesn't reflect a genuine Load Calculation for expected loads. Typically people wildly overestimate their loads. Or they buy a 100A or 125A maximum rated panel and think they are obliged to run 100A/125A wire to it. (not necessary; it's a "redline maximum" such as your car's 112 MPH tires). Or, they are choosing a "main breaker" panel and think their feeder must match that size. (no need). Or they hope the "near main" will trip before the "far main" (that doesn't work).

The upshot is that re-assessing the feeder size you actually need may result in smaller wires being feasible. So I would get out the sharp pencil and look at loads. A sidebar here: EV charging needs far less than you'd think. It wasn't designed by electricians to sell service upgrades. It was designed by SAE to sell cars :) They knew "needing a service upgrade" is a sale-killer, so they included tech to make it easy to avoid one, such as being able to use capacity that's there for peak needs (when you're not at peak). And you don't need a SPAN panel to do it; some of the most bargain-priced EVSEs (e.g. Emporia) support it. Right now.

Feeding into this is the problem of "not enough panel spaces". We say "spaces are cheap, regrets are expensive: think BIG on panel size". However that pushes you into larger, higher ampacity rating panels which can lead to the above confusion. Don't search for that "black swan" 30-space/100A panel; use a 30-space 200A and run a 90A feeder to it if that's your requirement.

And a trick one can use is to use EMT metal conduit. This is thin-wall conduit, which makes it overall slimmer than PVC for the same interior size. You can mix-and-match conduit types just by using appropriate couplers - typically you go to a threaded connector then use a female/female coupler.

Obviously if you're mixing EMT and non-metallic conduit in a run, you can't very well use the EMT shell as your ground wire, so you'll need to run a ground. On the other hand, an EMT run continuous between two metal boxes could serve as the ground wire for that section.

Conduits can have pulling points

Because of the "build complete, then pull" rule, conduits are allowed to (often required to) have "pulling points" enroute. One common type of pulling point is a "conduit body" such as a type C (straight through) or "LB" (90 degree elbow; top door). To be clear: splices do not happen in conduit bodies. They are for access to ease pulling forces.

But, conduit bodies also make a great place to transition conduit sizes. I like the idea of 1-1/2" conduit on the long run underground - makes for an easier time pulling. However, you could come into a conduit body (say: an LB at the building entry) and then transition to smaller conduit for additional distance.

For instance I mentioned EMT conduit: you don't need a conduit body to change conduit type but I strongly recommend it for changing conduit size. (you don't want a reducing step in the middle of a run, because it'll snag anything you pull, but with it right next to a conduit body you can coax it past.)

For 1-1-1-6 AWG (copper or aluminum) you need 1-1/4" conduit minimum.
For 2-2-2-6 AWG you also need 1-1/4" minimum.
For 3-3-3-8 AWG (copper only) you can just make it on 1" conduit.
For 4-4-4-6 you still need 1".
6-6-6-8 can do it with 3/4" conduit; in copper this is 65A wire (breaker at 70A) and in aluminum it is 50A wire.

Or you can splice in a really big box

And this seems like a good option to go aluminum where size isn't critical and copper where it's critical. However, the connectors aren't cheap. Generally one uses Polaris connectors for wires larger than #6. Those start at about $20 each, so you're into $60 for a 3-wire feeder, assuming you find an alternate way to splice ground. The ILSCO Mac Block Connector is a "mini Polaris at a mini price" for #14-#6 wire, but it's hard to find.

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  • 1-1-1-6 less than 24" long in IMC, LFNB, LFMC, RMC (but not other types) meets the 60% fill nipple rule for 1". Delete the ground wire and use metal boxes, and 1" EMT also works under the nipple rule. So if the transition junction box is less than 24" from the panel...
    – Ecnerwal
    May 20, 2023 at 11:05
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Not without a junction box and a transition to cable. The wires alone without conduit are not an acceptable wiring method in-wall or out.

They have to be in conduit (you can change type of conduit, and if you have a box to transition, you can change to smaller conduit under the "nipple" fill rules for a section less than 24" long.)

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