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Thread: Shop electrical wiring - EMT vs MC cable

  1. #16
    One thing to note is MC cable is subject to the same requirements as NM cable "Romex®" to be protected from physical damage.

  2. #17
    When I moved into my latest shop I ran just regular romex along the ceiling then had 3/4” pvc conduit from the top of the ceiling down the wall with a outlet or directly wired to my machines. If I had it to do over I would have used all MC cable.

  3. #18
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    If you do go with MC you should get an MC cable spitter and also remember to use the red head inserts

  4. #19
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    How about flexible metal conduit?
    "Anything seems possible when you don't know what you're doing."

  5. #20
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    I'm planning to run Romex for the lights and EMT surface mount for the shop portion. set up a laser in the middle, and start going around the shop at about 4 ft with quad boxes and sticks of 3/4. run 2 20 amp circuits and each box will be split. a few 50 amp outlets spread out for welding or large machines. pulling wire is really pretty easy as long as you keep the runs under 20 feet or so.

  6. #21
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    Adam, give serious thought to moving the conduit up near the ceiling. My old shop was like you're talking about and in was a PITA. It was constantly in the way for hanging stuff on the walls or cabinets. I did the current shop with the EMT near the ceiling and drops to outlets and switches. It added a minimal amount to the cost and it is much more user friendly.

  7. #22
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    Quote Originally Posted by Lisa Starr View Post
    Adam, give serious thought to moving the conduit up near the ceiling. My old shop was like you're talking about and in was a PITA. It was constantly in the way for hanging stuff on the walls or cabinets. I did the current shop with the EMT near the ceiling and drops to outlets and switches. It added a minimal amount to the cost and it is much more user friendly.
    I agree. Use the area near the ceiling for horizontal runs & just drop straight down to outlets. It makes changes easier and the pipe doesn't get in the way of other fixtures you may want to wall mount.

  8. #23
    Thanks for all the replies. It’s given me some food for thought.

    If MC cable still had to be protected from damage like Romex (in a code approved environment) then what’s the point of using it for drops, etc if it still needs additional physical protection?

    Everything I’m planning to do will either be surface mounted on the walls or strapped to the bottom of the metal truss at the ceiling (lighting, maybe some tool receptacle drops.)

    Leaning towards EMT along the upper walls at this point. I haven’t made a detailed and confirmed shop layout or lighting plan yet. I’m sure that step will help inform how my actual wiring needs to be.

    I see that THHN is a sold / separated as single conductor wire. Can you bunch a few (3 or 4) together and then pull through the EMT (physically/practically speaking) or is it fished and pulled to location one wire at a time? Is pulling wire in a shop this size a serious labor factor or consideration if I’m doing this largely alone?
    Still waters run deep.

  9. #24
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    You typically pull multiple THHN conductors at the same time between pull points...so some planning is required, both to insure you have the conductors you need (and mark them so you can differentiate) and so you have the correct size conduit to not violate fill maximus.

    I admit I'm also perplexed that MC would require additional protection given its nature. But I only know enough of the code to be dangerous. Almost all of the buildings I've seen, either directly or in videos have had MC fully exposed. My electrician even mentioned it, not knowing I was going to be fully finishing my building inside. His own post frame structure is bare. Based on a little "searching" it seems that there is a provision in the code that MC must be protected where it might be subjected to damage but can be exposed otherwise as long as it closely follows the surface of the structure. The former part of that is likely subject to interpretation. So in the metal building, if it follows the structural members so that it's not exposed to physical abuse, I would think that is allowed. I suggest you have a conversation with your local building/code officer to understand what they would allow for your type of building and for how you'll be handling your walls, etc.
    Last edited by Jim Becker; 05-05-2022 at 9:17 AM.
    --

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  10. #25
    Phillip,
    As Jim stated, you bundle and pull especially with first run through empty conduit. I'll reiterate 2 points:
    1> go with a larger, 3/4" EMT. It makes pulling easier, and if you add a circuit in the future, you've got some allowable space if you're using 12 -10 gauge.
    (Google EMT conduit capacity to find out how many of a given gauge can be run inside.) This may get you thinking of just going with an over-sized 1-1.5" conduit, but look at price and reduced flexibility/availability of fittings vs. the more common, smaller sizes, hence the emphasis on 3/4.

    2> The spacing of your outlet boxes, say 6', allows you to run short lengths, which are super-easy to pull. This means you are daisy-chaining at each junction box, so even though you may run a 24 ft length, it's made up of 4 6' lengths. I almost didn't need the cable pulling fish-tape I bought. Often, when adding another circuit, I'll simply push-pull one conductor at a time to ease feeding through an already populated conduit run. Bend feed end over into a hairpin shape to help avoid hangups as it slides through.

    There will likely be some dedicated circuits running further down the line that you'd rather keep intact vs. packing more wire nuts into each junction box, but even then, it can be helpful, as you can monitor your progress at each 6' junction box. Just opening the junction boxes allows you to see your progress and help feed it through.

    I've always been able to do this work alone, as it's no sweat, as described above. No tug-of war. Just don't over-pack the conduit. Consider separate conduits for the 3phase equipment, as it typically utilizes larger 10 up to 6 gauge conductors, and as you research, you'll likely find squeezing any more in the 3/4 won't meet code. Physical capacity seems obvious, but heating is also a concern if you over-pack that conduit.

    jeff

  11. #26
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    I would definitely choose EMT. Get a "conduit hand bender". After two or three bends, you will be comfortable with any angle and little jogs around obstacles.

    Run larger conduit, and you can run a fish tape through it for later changes. I pull a strong twine through my conduit with the wire to facilitate pulling subsequent mod's without a fish tape. It's also easier to pull additional wire later if you untwist/unspiral the initial wires before pulling them.

    Check with your inspector before relying on the conduit for ground. They are trying to get away from it because a few clamp screws or box nuts inevitably loosen and fail to make a trustworthy ground. Using the conduit also means you cannot use plastic or fiberglass boxes.

    Individual wires (e.g., THHN) are a LOT easier to pull around bends through conduit than Romex. The comment about untwisting applies extra if pilling Romex!

    If you have long runs and/or a lot of bends, pulling is easier with lubricant made for the purpose, but I've never needed it in over 40 years. Check the code if you have a lot of bends, as you may need "pull corners" -- with a variety that's nice for sharp right-angle bends, e.g., to enter a wall or cabinet from a flush conduit run.

    I ran conduit from boxes, up the wall, to junction boxes on the top plate or rafters. I ran Romex above the rafters and in the wall between the (covered) studs for the breaker box and connected to the vertical wall runs at the junction box at the top. My rafters are exposed, but the inspector had no problem with Romex crossing between rafters. Another city, same state (CA), required me to run a 1x4 across the rafters and staple the Romex atop the 1x4 -- inspector said his guideline was to not damage the Romex if you hit it with the sharp edge of something while maneuvering it.

    Have fun.

  12. #27
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    No one mentioned plastic conduit, but if anyone uses that, a heating blanket is worth having to bend it when you run into an odd offset. Mine is a Greenlee, but I expect there are cheap Chinese ones now.

    In the original part of our barn I used metal conduit, but in the additions I used plastic. It's 42 years old now. We've never had any problem with any of it, and that's in the service of horses which you would think would be subject to more abuse than a woodworking shop. I don't think plastic looks any worse than metal.

  13. #28
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    I personally like the PCV conduit, Tom, at least historically for the way I've used conduit. It's easy to install for sure. It's what I have in my temporary shop for machine circuits now.
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  14. #29
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    Lots of good advice here. I'll just add a few comments.
    Quote Originally Posted by Wayne Cannon View Post
    I would definitely choose EMT. Get a "conduit hand bender". After two or three bends, you will be comfortable with any angle and little jogs around obstacles. Well, that depends on the complexity of the run. There's a real art to a good EMT installation. Lots of electricians never get good at it. But what is done in a home shop can be planned out so you only have to deal with elbows, box offsets and kicks. That's all simple stuff and there are loads of videos showing how to do it.

    Run larger conduit, and you can run a fish tape through it for later changes. I pull a strong twine through my conduit with the wire to facilitate pulling subsequent mod's without a fish tape. It's also easier to pull additional wire later if you untwist/unspiral the initial wires before pulling them.When pulling wire in after it's easy to abrade the insulation. Not having the wires twisted will help a lot with that. I always you wire lube when doing that as well.

    Check with your inspector before relying on the conduit for ground. They are trying to get away from it because a few clamp screws or box nuts inevitably loosen and fail to make a trustworthy ground. Using the conduit also means you cannot use plastic or fiberglass boxes. I agree. I've personally seen the sparks fly when there's a short circuit and the the conduit fittings are not well bonded.

    Individual wires (e.g., THHN) are a LOT easier to pull around bends through conduit than Romex. The comment about untwisting applies extra if pilling Romex! Check your code. Here Romex in conduit is not allowed because it isn't approved for that. It is allowed (at the inspector's discretion) for short lengths where it is used as a sleeve for mechanical protection. If it's metallic, it must be grounded.

    If you have long runs and/or a lot of bends, pulling is easier with lubricant made for the purpose, but I've never needed it in over 40 years. Check the code if you have a lot of bends, as you may need "pull corners" -- with a variety that's nice for sharp right-angle bends, e.g., to enter a wall or cabinet from a flush conduit run. Pull elbows, which are short with an angled cover can be very difficult to use when there are more than just a few wires. Better to use an LB fitting, which has a lot more room.

    I ran conduit from boxes, up the wall, to junction boxes on the top plate or rafters. I ran Romex above the rafters and in the wall between the (covered) studs for the breaker box and connected to the vertical wall runs at the junction box at the top. My rafters are exposed, but the inspector had no problem with Romex crossing between rafters. Another city, same state (CA), required me to run a 1x4 across the rafters and staple the Romex atop the 1x4 -- inspector said his guideline was to not damage the Romex if you hit it with the sharp edge of something while maneuvering it. Romex can be run on the top of in an attic, but if there is more than 3' of clearance, you need to run a board beside it to protect against being walked on.

    Have fun.

  15. #30
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    Quote Originally Posted by Wayne Cannon View Post

    …. Check with your inspector before relying on the conduit for ground. They are trying to get away from it because a few clamp screws or box nuts inevitably loosen and fail to make a trustworthy ground. Using the conduit also means you cannot use plastic or fiberglass boxes.

    Individual wires (e.g., THHN) are a LOT easier to pull around bends through conduit than Romex. The comment about untwisting applies extra if pilling Romex!

    Have fun.
    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.

    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.
    What you can not do is remove the sheath when pulling it. NEC says the conductors must be listed and labeled. Romex is typically labeled on the sheath with no labeling on the individual conductors.
    No label, no use. A nitpicking type fauxpas that will have many inspectors looking the other way while checking a job if it is a short run in a dry location, but a violation nonetheless.
    But when pulling nm-b through conduit you must use largest dimension (width) when computing conduit fill and not its actual cross-sectional area. That means upsizing your conduit in many cases. For example 1/2” emt can house ten #12 thhn conductors, but only one 12-2 with ground romex cable.
    Comments made here are my own and, according to my children, do not reflect the opinions of any other person... anywhere, anytime.

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