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Thread: Conduit Bending 101

  1. #16
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    Julie, thanks for posting this! It's on my list for my new shop. The runs to each of my major machines will be in conduit, as well as a few circuits for my 110v machines. I figure it's much easier to reconfigure my shop if the major wiring is in conduit rather than in the walls (which will be spray foam insulated).

  2. #17
    Ole,
    This just shows my ignorance when it comes to electrical, so I went out and bought a book today to learn something. I think I'm just going to run 10/2 wire, since it will be for 240 only. I was also thinking of running another circuit in there as well for some additional 120, probably #12 for that one. I would like to run them all in one conduit, so that's why I was thinking 3/4. I'm learning a lot, with tons more to go!
    Steve

  3. #18
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    Steve,

    10/2 implies romex type of wiring. That cannot go within a conduit. Only single wires can be pulled through conduit...THHN. Most of the orange and blue boxes carry such wire. Romex is already sheathed in its own conduit so to speak.
    Wood: a fickle medium....

    Did you know SMC is user supported? Please help.

  4. #19
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    Quote Originally Posted by Steve Wilde View Post
    Julie, I have a quick question about what size conduit to use. I will be putting three wires through the conduit if that is ok. Two circuits of 240 and one 120 circuit. Would that all fit in a 3/4 conduit or would that be too tight? I am going to go out looking at the local pawn shops for a cheap bender today and want to get the right size. Thanks again!
    If we start from a point of accepting that our crystal ball can't predict what we will want or need in the future, and anyone who has been there knows the crystal ball usually lies, it's a good idea when installing conduit to load it on the light side.

    We're talking workshops and I think we'd be nuts to fool ourselves into installing 15A receptacles with #14 wire in a workshop. So let's assume every wire we pull will be #12 or larger, if the load requires it. With single phase panels, we have (2) hots and (1) neutral. That makes up one network.

    If you are installing 1/2" pipe, be kind to yourself and only install (2) networks - a total of 6 wires. I'm sure there are many here who would tell you what a pain it was trying to push a fish tape through a conduit loaded with wires, after they realized they needed another circuit, a switch leg or some other wire downstream. Leave yourself some room for the future.

    In commercial construction around here, it's a minimum #12 wire and 3/4" pipe. That's because experience has told us changes will be made. So why not treat your shop that way?

    If I can get you to imagine sometime in the future... You just bought a new jointer and you want to install a receptacle for it. But to do so, you have to run another conduit from your panel. And the last time you did that, it was a pain.

    Now imagine you installed a larger conduit, or loaded your conduits lightly and all you have to do is pull in some new wire. You'll be patting yourself on the back for thinking ahead. It's a nice feeling.

    Which scenario do you like better?
    Last edited by Julie Moriarty; 03-23-2015 at 11:47 PM. Reason: typo

  5. #20
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    Quote Originally Posted by Ole Anderson View Post
    Although the answer will ultimately come from the NEC conduit wire fill tables.
    Ole, I have said before I'm no fan of NEC wire fill maximums. It leaves no room for future expansion and it can be a bear to pull. Going light on wire fill is a good mantra, and you won't have to worry about violating the NEC or your local codes.

  6. #21
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    Quote Originally Posted by Steve Wilde View Post
    Ole,
    This just shows my ignorance when it comes to electrical, so I went out and bought a book today to learn something.
    Sorry, Steve, I should have said this before. If you want a very handy and simple book to help along the way, buy Ugly's book. I'll bet 75% of the electricians I've worked with over the years had one in their tool bag or on their person at any given time. I probably went through three of them myself. Do a web search and find the latest issue. Buy it. And use it!


  7. #22
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    Before we go into offsets and saddles, we probably need to discuss the use of the ARROW and the STAR on a bender. As I mentioned before, when using the ARROW mark, you subtract the TAKE-UP from a the overall measurement you need - to the BACK of the 90.

    When using the STAR, you do not need to subtract anything BUT you do need to flip the bender around.



    In the top picture I am ready to mark the pipe for a 24" 90. The tape measure has 19" lined up at the ARROW - 24"-5" TAKE-UP=19". From there you stand the bender handle up and make your bend. Note: the heel of the bender is on the opposite side from the end of the pipe. The end of pipe (start of the measurement) the will come off the floor as you bend.

    In the bottom picture I've flipped the bender around, in relation to the direction of the bend. Now I have set the POINT of the STAR right on 24". In both cases we end up with a 24" 90. But in the bottom picture, I didn't need to subtract the TAKE-UP but I did need to flip the bender around. Note: the heel is now on the same side of the handle as the end of the pipe. The end of pipe (start of the measurement) the will stay on the floor as you bend.

    The STAR is used for many different applications but for now we'll stick with two common uses.
    1. The Long 90 - If you are bringing pipe out of a low receptacle box and up into the ceiling joist space, the measurement to make that bend might be 85" or more. Rather than making a mark at 80" and sending 80" of pipe up into the air, you put your mark at 85", flip the bender around as in the lower picture, and then make the bend.

    2. The BACK TO BACK 90 - In this case you have to come up out of a box, 90 over a distance, then 90 back down to another box. You might need to get up and over something or you can't come out of the side because the box is nailed to a stud.

    As you can see in the drawing, the center-to-center measurement of the pipe (and box) is 48". But the BACK TO BACK measurement is 48-3/4". That's because the measurement is taken from the BACK of each 90. Since this is 1/2" EMT, that means if you had a center-to-center measurement you'd need to add 3/4", the OD of 1/2" EMT.

    The two arrows point to where the marks will end up AFTER the bends are made.

    In this case, the first bend was made using the ARROW. It was a 14" 90 so the first mark was made at 9". Then the first bend is made. Once you make that bend, you measure from the BACK of the 90 you just made and mark the pipe at 48-3/4". Then you flip the bender around and set the mark at the POINT of the STAR and bend. To make sure you are right on the back of the first bend, you can take any straight edge (a piece of pipe will do) and lay it against the back edge of the first 90.

    Any questions?

    Additional help for those who like to learn from books:

    If the yellow one is the same thing that used to come with the Benfield shoe (they used to sell just the shoe and you had to make your own handle) this is a good guide. Both are available at http://www.benfielddirect.com/. The one on the right is also at Amazon

    Someone said this one was better but I've never seen it so I can't vouch for that.


    Before you buy any bending books, instructions usually come with a new bender. I'm pretty sure instructions come with Ideal benders. And from what I can see of benders selling today, it looks like Klein would be just as good a choice as Ideal. Good benders last a lifetime so if you can get one at a flea market or off Ebay, do it and save some money.

  8. #23
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    Quote Originally Posted by Chris Padilla View Post
    10/2 implies romex type of wiring. That cannot go within a conduit. Only single wires can be pulled through conduit...THHN. Most of the orange and blue boxes carry such wire. Romex is already sheathed in its own conduit so to speak.
    I have a project coming up and wanted to verify that exact statement. Reading the 2014 NEC I could not, contacting my AHJ could not (which is mostly moot as he is not an electrician), and none of the three electricians I spoke with could. At the same time, the electricians included the caveat they have never needed to but upon there (quick) review of the NEC from their truck, could not.

    But there is a catch. Although NM-B cable is approximately 1/4" by 1/2" oval shape (0.125 sq in), the conduit fill requirements in the NEC mandates the fill for NM-B cable be based on 1/2" diameter (0.2 sq in). So it is allowed but you take a hit.

  9. #24
    This is great stuff Julie. Thanks so much for taking the time to share your experience and skill with us.
    “If liberty means anything at all, it means the right to tell people what they do not want to hear.” -- George Orwell


    Money is simply the marker used as tools move thru the galaxy to their best-use destination. - Kent Bathurst

  10. #25
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    Quote Originally Posted by Julie Moriarty View Post
    Now imagine you installed a larger conduit, or loaded your conduits lightly and all you have to do is pull in some new wire.
    With regard to planning for future expansion, is it advisable (or even permissible) to include a run of poly twine with the initial conductors to allow for easier pulling of new cables later or do you just suck it up and use a metal fish tape when the time comes? The circuits I'm thinking of adding to my shop will probably be 50-60 ft from end to end, seems like a lot of work to run a fish tape through all that distance.

    I've used twine when pulling long runs of ethernet cable and it sure comes in handy the next time I need to add a cable - just attach the cable (plus another run of twine) to the original twine and pull...

  11. #26
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    Nice clear instruction. Where were you six months ago when I needed this?

  12. #27
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    Marty, on a run as long as 50'-60', yes include a pull string in with the wires. But you have to be careful how you feed them in or the pull string will get twisted in with the other wires and when you go to pull in wires later on, you could have a bear of a time snaking it through the existing wires. When we're pulling big cable, we train them in, in the same formation all through the pull so they don't cross over one another. You can do that with smaller wire but it takes a bit more time. When wires cross over each other, they tend to become much harder to pull in and get out later on.

    There is a high strength pull string made just for pulling through conduit. The string we use on the job comes in 5 gallon buckets but you may be able to get it in shorter lengths. If you do get some pull string, you can tie a Baggie (the cheap kind - no zip seals) to the end of it, loosely stuff the baggie in the pipe and take a strong vacuum to the other end, press it down on the pipe and the Baggie & string will zip right through. No fish tape needed.

    For anyone buying a fish tape, if you can find the slinky type (Sparks or similar), you'll appreciate how much easier it is to send through the pipe, especially when there's wire already in it. If you don't make a the pulling head right on the steel tapes, they could be a problem if you get stuck and have to pull it out. I was an apprentice when I found that out. I couldn't get the fish tape through an existing pipe with wire already in it. The pulling head (the loop) was open a bit. When I went to pull it back to regroup, it dug through the insulation of a wire and I heard a pop. Oops! The journeyman I was working with was pretty cool. We pulled out the existing wire and repulled with the new wire we needed.
    Last edited by Julie Moriarty; 03-24-2015 at 4:41 PM.

  13. #28
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    Before we go into offsets and saddles...

    Getting an accurate bend: I mentioned before that when using a level, you have to make sure the surface on which the pipe sits is level. In this picture, the bubble is good on the stub up (I know it looks off but it's the wide angle lens), but the bubble on the bottom level shows the floor is not level at that point. Most concrete floors have small peaks and valleys, so you can move the pipe around until you find a level spot, or place a wedge underneath one end so the horizontal section of the pipe is level.


    Measuring the bend:

    Here, that 10" 90 looks like it's actually 10-1/4". But if you look closely, you can see a gap between the floor and the bottom of the 90. The weight of the outer end of the pipe is resting on a surface not parallel with the surface under the 90.


    When I place my foot close to the 90 I get a 10" measurement. Get in the habit up making sure the 90 is sitting on the floor when making this measurement. BTW, that 1/4" may not seem like a big deal, but it can become one, depending on the installation. When tolerances are very tight and what you are installing to doesn't move, you may find that 1/4" a real pain to deal with.

    IMPORTANT! Always make sure the conduit seats fully in the coupling or connector! The conduit and boxes all connect to the panel and make up your case ground. You don't want a weak or faulty case ground. Cuts should be square and the pipe needs to be fully into the fitting. If you're using set screw fittings, the set screw can dimple the end of the pipe in and expose it as a hazard to wire pulling and the insulation.

  14. #29
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    Stretching and Shrinking a Bend

    Let's say the 90 you just made was a bit too short or a bit too long. We're talking an inch or so. If it's too long you can cut it but if it's too short you can't add to that because the coupling is longer than what you need to add. In either case, you can stretch or shrink the pipe faster than the band-aid methods.

    Let's say that 10" 90 is about 1/2" too short. Maybe the pipe slipped in the bender before you started the bend or you mis-measured or you had a senior moment. It happens. But there's an easy fix.

    You have to start by taking some bend out of the 90. In this case I want to stretch the 90 so I need to take bend out closest to the top of the stub.

    Because the 90 is only 10", I have to place a lot of pressure on the end of it with my foot. With your hands firmly on the pipe, I begin by opening the bend, pushing out and somewhat down, to make sure the bend is opening at the floor and not in the middle or higher.


    You can also place the end of the 90 inside the handle but you have to make sure you don't deform the end of the pipe or kink the pipe where it exits the handle.


    Here, you can see the original pencil mark that was placed at the ARROW in the first bend is now outside the the bender completely. I know from experience that the amount of bend I took out and the placement of the original mark, relative to the ARROW, will give me about an extra 1/2". This is not an exact science. You sometimes have to mess with it a while until you get the measurement needed.


    Now I've gained 1/2" over the original 10" measurement. If you need more, you have to take more bend out and slide the original mark a bit farther out. Practice with a bend and you'll get the hang of it pretty quickly.
    Last edited by Julie Moriarty; 03-25-2015 at 11:31 AM. Reason: typo

  15. #30
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    But what if you need to shrink the 90? Sure, you can cut the end and ream it. But you can shrink it in less time. It's pretty much the flip side of stretching.

    In this case you had another mental moment and instead of a 10-1/2" 90 you actually needed a 9-1/2" 90. Now you need to shrink the stub length by a full inch. And to add insult to injury, this will be harder because you have such a short 90.

    If the 90 is short (like this one), place the handle of the bender over the pipe. With handles that have belled ends, you can slide it down further onto the 90. This is a good thing. As before, make sure you are taking bend out at the floor, or in this case, farthest from the end of the 90.


    We've taken more out of this bend than the previous one because we need to change the dimension 1" now.


    Here, you'll need to concentrate most of the force on the foot. Your foot should be applying 80-90% of the force when making this bend. I have one hand on the end of the handle and the other on the pipe. When you jam down with your foot, let your hands help a bit in making the bend but make your foot do most of the work. Think like the force of your foot is doing all of the bending.


    This took me three "shots" to bring the bend back to 90 degrees. Each began with as much foot pressure as I could apply downward and suing my hands to guide the direction of the bend. DON'T ALLOW THE PIPE TO COME OFF THE FLOOR! If the 90 comes off the floor, all the force will be absorbed by the end and you will most likely deform it. With smaller pipe you can fix that with Channel Locks but try not to let that happen, if possible. Very short stubs make avoiding this difficult.


    Now we've taken the 10-1/2" 90 and shrunk it back to 9-1/2". This is faster and easier than setting the pipe up it to cut it, picking up the hacksaw, cutting it, reaming it, and then returning to where you're working.


    If you look at the radius on the pipe vs. the radius of the bender, you can see they aren't the same anymore. This happens when stretching or shrinking bends. And the more you mess with it, the harder it is to keep close to the original radius. If you had a bunch of conduits coming up out of a panel to the ceiling, and you want them to look nice and uniform, you don't want to get into stretching or shrinking the pipe. The difference in radii will be obvious. Measure twice, bend once.

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