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I'll be running some new circuits inside my unfinished attached garage in order to provide some new outlets on the other side of the garage. EMT conduit will run about 20' along one wall, then turn 90 degrees and continue another 20' along the adjoining wall. At some point in the future I may wish to add an outlet halfway along one or the other conduit run, so I plan to include inline 4x4 junction boxes halfway along each segment. The wires inside the EMT will be either 12ga or 10ga THHN/THWN. In order to make things easier to connect in the future, should I leave a perhaps 1 foot loop in each wire where it passes through a junction box? It won't be connected/cut/spliced there (yet or perhaps ever).

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  • I'm curious, why not just install the outlet now? You have the conduit, the box, the wires .... you're 5 minutes work and $5 from putting in the outlet. Why revisit this in future?
    – jay613
    Jun 19, 2023 at 16:30
  • @jay613 Don't have the GFCIs yet, nor a certain idea of exactly where outlet/switches/fixtures might go in the area. Lots of junk in/on the framing for wall and rafters that needs to be cleaned out and rethought. Garage is probably 80 years old and the original owner/builder used lots of "found materials".
    – Armand
    Jun 20, 2023 at 4:34

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Yeah, that's fine. Your maximum number of circuits per pipe is four, unless any circuits are over 28 amps, then you have to do some math.

Leaving a loop in each of your "possible future tap" junction boxes is a good idea. If you splice into a wire, you need 6" of wire length in the box, so if you leave yourself 12" + a bit, you'll be fine.

Don't feel obliged to throw wires into the conduit now. If you are building conduit legally, you must pull the wires in only after the conduit is complete, so you can always add wires later. Do not build conduit that can't be pulled.

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    Also: if you don't put wires in, make sure you put a pull string in there. It's easiest to put one in at the start. I just added a circuit to a conduit today that I originally planned for two circuits. Since there was already a pull string, it took moments to get the wire in. Using fish tape it would have been a huge headache.
    – KMJ
    Jun 19, 2023 at 4:50
  • Using a vacuum and string it's easy-peasy to put a string in whenever.
    – Ecnerwal
    Jun 19, 2023 at 11:34
  • What's the deal with 28 amps?
    – Huesmann
    Jun 19, 2023 at 12:53
  • @Heusmann #10 wire is good for up to 30A per 240.4(D). However with 4 circuits in conduit, #10 is limited to 70% of its 40A rating (at 90C) due to 310.15(B)(3)(a) [NEC 2017 numbering]. Jun 19, 2023 at 18:00

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