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Thread: Shop electrical wiring - EMT vs MC cable

  1. #31
    Join Date
    Feb 2007
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    South Dakota
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    I really don’t get all this conduit stuff. I used pvc conduit in my last shop because the walls were already finished. I used metal in the previous place also because the walls were all finished before I bought the place. But for a new build I don’t get it. Just put a 110 and a 220 outlet every 8 feet all around the perimeter. You’ll already have power any place you need it and will never have to tap into the system again. Just use 12 ga cable and put it up before finishing the walls. If you are really concerned about needing to add more outlets in the future just surface mount all your boxes so they can be tapped into with conduit to extend a circuit in the future.
    I think some people just think a shop should have conduit because of the industrial look. I just see another place for dust to collect. The same goes for all the dust collection pipes. I put my pipes above the ceiling with vertical drops to the machines to eliminate horizontal surfaces that also collect dust. You can always tap into a vertical drop and extend the system under the ceiling in the future if needed.
    But that’s just me. Carry on.
    The Plane Anarchist

  2. #32
    Well, the reason I want to do surface mounted (no wires in the walls) is because I’m planning to use closed cell spray foam in the wall cavity and would rather keep all electrical out of the spray foam for future proofing and the inevitable machine moving and additions. I have remodeled/had to re-wire in a few situations with closed cell spray foam and it’s a nightmare and obviously degraded the R value in the wall when you have to remove foam. Locating and modifying existing wiring inside of closed cell spray foam is not something I would recommend to anyone. Hence moving everything to surface mount on the wall covering itself for maximum flexibility in future modifications.

    I don’t really care what the wiring looks like personally as long as it’s safe...just seems like some form of conduit is the sensible way to go after a certain threshold of shop size and future flexibility.
    Still waters run deep.

  3. #33
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    So just surface mount all the boxes. You can tap into them with conduit anytime you want in the future. Its seams like a lot of waste for something that might happen in the future.
    The Plane Anarchist

  4. #34
    Join Date
    Apr 2013
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    Okotoks AB
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    Some more comments I'll add.
    Quote Originally Posted by Charlie Velasquez View Post
    Checking with your inspector is always good advice.
    I am surprised that “they” are trying to get away from using metal conduit as a ground. Studies have shown properly sized and installed metal conduit systems are superior to aluminum or copper conductors for clearing a fault. https://steeltubeinstitute.org/wp-co...ing_042820.pdf is one such study. True, the conduit may have lower resistance than a ground wire just by virtue of the much higher cross sectional area of the conduit. Where that breaks down is typically at the box connectors, particularly painted enclosures. And the threads on those connectors are not precision and often do not tighten well. One case I saw was on a 200A switch. there was a phase to ground short and the ring on the concentric knockout was completely blown out

    Wrt untwisting wires if pulling Romex (nm-b) through conduit…. I’ll assume you are speaking of pulling multiple romex cables and not the individual conductors.
    There is no NEC prohibiting pulling Romex through conduit. In fact, in some cases it may be required. The CEC does not allow non metallic sheathed cable (Romex to you Americans) to be pulled in conduit. If there is a short section that requires mechanical protection, it is generally allowed to use a length of conduit. But then they call it a sleeve so they don't have to break their own rule.

  5. #35
    OP...I would be doing most of the physical wiring after the initial inspection of minimal electrical from my electrician (panel and a couple of circuits with a few receps and lights to pass inspection.)

    ........That's what most of us do and probably why there's so much electrical stuff at the Home depot.




    I'm not a big fan of surface mounted conduit but sometimes it's the path I take
    27B92D5A-B90F-4745-9218-BC80B6FE7F6B_1_201_a.jpeg


    this is my homemade electric 15,000watt glass furnace and wiring....
    7FD5EE7E-ED8F-4EF0-A456-FEFC5309AF66_1_201_a.jpeg



    sure, call the inspectors
    C7964602-2E8A-4396-9A72-ED2E7B0B5C81_1_201_a.jpg

  6. #36
    Join Date
    Mar 2003
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    SE PA - Central Bucks County
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    Quote Originally Posted by Lawrence Duckworth View Post
    OP...I would be doing most of the physical wiring after the initial inspection of minimal electrical from my electrician (panel and a couple of circuits with a few receps and lights to pass inspection.)
    This is actually how the electrical service for my new shop building is being handled by my electrician...a single 120v circuit and outlet to satisfy code and permit final electrical inspection. But, of course, whatever I wire up after that will be code compliant for obvious reasons. My plan for two 120v 20a utility circuits will definitely be "in the wall". 240v 30a circuits may be "in the wall" or surface mounted via conduit. I have not decided yet...'need a building first to be able to visualize things better in that respect.
    --

    The most expensive tool is the one you buy "cheaply" and often...

  7. #37
    Quote Originally Posted by Jerome Stanek View Post
    If you do go with MC you should get an MC cable spitter and also remember to use the red head inserts

    While I use redheads, they are NOT required for MC cable in the NEC, like they are for AC cable. The Seatek brand cable splitter is the best in my opinion, they are not all the same.

  8. #38
    Join Date
    Oct 2011
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    Seattle
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    I built my 1500sq ft shop with the old barn timbers from our Il. farm--shipped to Seattle when deadhead container shipping was really cheap-- and mimicked the exposed MC wiring that all the pre-1900's barns had. My electrician is a friend and installed the minimum to pass inspection and I finished the rest with MC cable. He thought I was nuts and said he could do conduit faster and likely for the same cost--if you add in the MANY trips to HD to get the components I forgot to get on the last two trips!! I ran eight individual 220 circuits and MC made it easy to do for a DIYer and has been an advantage when I have reconfigured the shop layout. I chose it for the aesthetic for an old barn look but I think for a new shop the PVC conduit would be as easy and still not be a big issue if you wanted to move things around. Good luck,

  9. #39
    Join Date
    Sep 2016
    Location
    Modesto, CA, USA
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    I see some confusion here. MC and MFC are two very different things. MC is metal clad cable with preinstalled wires. You can not add or remove the wires, too tight. FMC is flex metal conduit sold empty just like EMT. You can add and remove wires like you can with EMT. I think the allowed fill amount is smaller for FMC.
    Bill D

  10. #40
    Join Date
    Mar 2009
    Location
    central tx
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    If you space enough boxes out across the shop walls and ceiling I don't think you should need to plan to modify a lot. Its really only if you are trying to save money up front, but the cost of the THHN vs romex adds up quickly.

    FWIW I ran surface EMT all over my garage and then when I built my shop I just overdesigned it and ran everything inside the walls and had it spray foamed.

  11. #41
    Quote Originally Posted by Bill Dufour View Post
    I see some confusion here. MC and MFC are two very different things. MC is metal clad cable with preinstalled wires. You can not add or remove the wires, too tight. FMC is flex metal conduit sold empty just like EMT. You can add and remove wires like you can with EMT. I think the allowed fill amount is smaller for FMC.
    Bill D

    Some people confuse MC, Metal Clad cable, & AC, Armored Cable, two different products covered by different articles in the NEC, and have different installation requirements, flexible metal conduit is as said a entirely different material available in steel & aluminum versions, and all need to be protected against physical damage just like NM cable.

  12. #42
    Join Date
    Mar 2010
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    Somewhere in the Land of Lincoln
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    When my shop was wired we ran 1" and 3/4" EMT. I have 10 240 volt circuits with 8 gauge wire but on 30 amp breakers (then if I have a need for the higher amperage it's merely a breaker change) and I think 10 but it might be more 120 volt circuits all with THHN. 200 AMP service dedicated to the shop. The lights have their own EMT runs on the ceiling. My shop is 30' by 56' by 14'. The conduit is mounted between 44" and 48" up the wall. While I understand the point you make Lisa I have my cabinets all free standing. The top 10' of the wall is white metal building tin and I didn't want to put any holes in the tin. I might have had watery eyes when I put the vent through the wall for the floor heat.

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