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Thread: Conduit Bending 101

  1. #31
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    I'd like to come back to Julies excellent thread as reference material periodically, maybe should be stickied to the top of this section of the forum?

  2. #32
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    Offsets:

    There are a number of ways to build an offset -
    1. You can keep making bends until it works (good luck)
    2. You can use a center of bender mark - it takes some practice but once you learn it, it's pretty foolproof, as long as you know your bender well, and that takes a bit of time.
    3. You can use a "multiplier". This is the easiest and only requires you make both bends the degree that corresponds to the multiplier.

    The Multiplier:
    If you are going to make the offset bends 30 degrees, the multiplier is 2. For a 5" offset, center-to-center, you take the offset dimension and multiply it by 2. (5x2=10) When marking your pipe, the distance between Mark 1 and Mark 2 will always be 2x the offset dimension for a 30 degree offset. In this case, 10". When you measure, make sure you get a CENTER-TO-CENTER measurement! If it's easier to get an overall measurement, just subtract the O.D. of the pipe.

    These are the multipliers for common offset bends.


    Here's one example:
    Let's say you need an offset that is 4" center-to-center. And the first bend needs to be at around 8" from the end of the pipe.


    Here I've marked the pipe at 8" and at 16". The 8" mark is what I need to clear some obstacle, the 16" mark is the offset measurement X the multiplier + 8", my first mark. What's important is to make sure the first mark and the second mark are 8" apart for this 4" offset. When you make your marks, get into the habit of making them completely around the diameter of the pipe. You'll see why later.


    Now, this is important! What point on the bender you choose to align your first mark doesn't matter AS LONG AS YOU USE THAT SAME POINT FOR THE SECOND BEND! Here, I've chosen to use the end of the bender. You can see the 16" mark to the left.


    I've now made my first bend at 30 degrees. The first mark is still at the end of the bend. The 30 degree bubble is one of the many advantages of having that little conduit level. (even though it doesn't look it, it is on the mark, one problem of being model and photographer)


    I have flipped the bender around with the shoe in the air. You'll see why a couple steps down the page. You can see the 16" mark at the same point I had the 8" mark earlier. Since I made these marks all around the circumference of the pipe, I can see it when I rotated the pipe 180 degrees.


    With the second mark at the end of the bender, look down the pipe to check alignment. The picture on the left is rotated too far left, the middle too far right. What you want is what's in the picture on the right. (And even that's just a touch too far right.) From here on out, you have to keep some pressure on the pipe so it doesn't rotate or slip in the bender.


    You are going to make a partial bend now. One hand has to firmly grip the pipe CLOSE TO THE BENDER SHOE. Just as before, keeping pressure close to where the pipe is being bent is important, if you don't want kinks or irregular radii. Your other hand will be farther back on the pipe and you may want to brace your foot against the end of the handle that's resting on the floor. With larger pipe this becomes a must.


    You only have to make a partial bend. This does two things, it clears the end of the pipe and creates a bend that makes losing the rotational alignment harder. At this point you return the bender shoe and pipe back to the floor. Make sure the pipe doesn't slip or rotate. If it does, realign it before returning the bender shoe to the floor.


    With the partial bend already being made, the end of the pipe is off the floor, enough to allow the bender to rest firmly on the floor. Now you can finish the offset. As you do, you can either check the bubble for level (if you're using a level) or place a tape measure at the end of the pipe and stop bending once the bottom hits 4".


    With the bubble now reading level, the measurement from the floor to the bottom of the pipe is exactly 4". And the offset is parallel with the rest of the pipe.

    If you wanted a 45 degree offset, then you would have used 1.414 as the multiplier for the 4" offset. 4x1.414=5.656 or about 5-5/8". If your first mark was 8", your second mark would be 13-5/8". And your first bend would be 45 degrees. But you have to be careful about trying to make an offset that is difficult to impossible to build. If the multiplier dimension is too small, you'll find your first bend interfering with your ability to place the second mark at the proper point on the bender.

  3. #33
    This is a great thread, Julie!

    I need to make just such an offset bend in aluminum conduit for a machine project... very timely.

    I'm also going to acquire a Greenlee L77 level like yours. I found it on Amazon.

    Mike

  4. #34
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    Julie,

    Thanks for the great info. I've been putting off some badly needed improvements to the electrical layout of my shop and this is a great help in inspiring me to move forward on that.

    I for one would also like to see a thread on design. I've looked around for books and info on the internet but haven't come up with anything that deals much with design. Most of the literature only covers the basics. If you have any suggestions on where to look for some good information on that or if you can offer up a thread that covers it I would appreciate it.

    Thanks,

    Jim

  5. #35
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    Julie, you are a jewel! Thank you for a great thread. Patrick

  6. #36
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    Quote Originally Posted by Jim A Walters View Post
    Julie,

    Thanks for the great info. I've been putting off some badly needed improvements to the electrical layout of my shop and this is a great help in inspiring me to move forward on that.

    I for one would also like to see a thread on design. I've looked around for books and info on the internet but haven't come up with anything that deals much with design. Most of the literature only covers the basics. If you have any suggestions on where to look for some good information on that or if you can offer up a thread that covers it I would appreciate it.

    Thanks,

    Jim
    When you say "design" do you mean the wiring? Load balancing? Or just want your conduit work to look pretty? Or the whole shebang?

    I've been working on a basic design for a workshop that I will post here - a 1/2 garage conversion - to show how one might be laid out. It's very basic and doesn't involve the many obstacles we may encounter when doing the actual installation. If you have a specific layout - the loads involved, room for future expansion, etc - you could post it here and if I can help, I will. If it's really involved, we can PM or email and take it from there.

    FWIW, I will never do a conduit design that doesn't allow for future expansion. It's conduit and that opens the invitation to add wires that, based on what I've seen, is a temptation few can resist. Many municipalities around here built this into their electrical code. Some will only permit (2) 20A, 3 phase networks in a single 3/4" conduit. That's (8) #12 wires in a 3/4" pipe. The NEC allows about a million.

    For anyone who has never worked with a conduit system, I can guarantee you will go back and add wires later, unless you move first. If you work on a well designed conduit system, you'll never want anything else.

  7. #37
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    Quote Originally Posted by Julie Moriarty View Post
    When you say "design" do you mean the wiring? Load balancing? Or just want your conduit work to look pretty? Or the whole shebang?
    What I'm looking for is info on how to lay out multiple runs, how to do it efficiently and certainly aesthetically so that it doesn't look like a kludge when I'm done. Perhaps I'm just looking for certain rules to follow when laying out a shop.

    I will PM you with some more specifics. I may have more needs than what can be reasonably addressed here.

  8. #38
    Julie - this is off topic but you mentioned "load balancing". On an industrial job, does the power company require a level of load balancing across the three phases of a 3 phase system? Or is the single phase portion of the load generally so small that it doesn't matter?

    Mike
    Go into the world and do well. But more importantly, go into the world and do good.

  9. #39
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    Julie,

    Any tips on pulling wire through conduit? I.e., do you use any kind of lubrication? I assume you want to pull rather than push, which means using some kind of fishing line- how do you push the fishing line through the conduit?

    I pushed some wire through a 3 foot length of 1/2" conduit yesterday and have to admit, my cursing would've made nuns cry... and that was only 3 feet!

    Thanks,
    Peter

  10. #40
    Quote Originally Posted by Peter Aeschliman View Post
    Julie,

    Any tips on pulling wire through conduit? I.e., do you use any kind of lubrication? I assume you want to pull rather than push, which means using some kind of fishing line- how do you push the fishing line through the conduit?

    I pushed some wire through a 3 foot length of 1/2" conduit yesterday and have to admit, my cursing would've made nuns cry... and that was only 3 feet!

    Thanks,
    Peter
    I'm not Julie and I'm not experienced with conduit other than when pulling communication cables through them. Often as part of a build-out, I'm provided conduit through which to pull communication cables, the idea is to get a clean look to a reception area or something.

    So one time I was pulling more cables than what was anticipated because they decided they wanted more stuff at this location.

    An electrician gave me some lubricant that came in a big squirt bottle. There is no way I'd have been successful w/o that bottle of stuff. While I pulled the fish tape, the electrician held a towel under the bundle of cables entering the run and applied the stuff. Even WITH that goop, it was a challenge. Without it I was able to get about 1/3 the way and then the resistance was too much.

    I've done a little conduit bending but I'm terrible at box offsets (ugly) and will enjoy studying this thread for pointers.
    Last edited by Phil Thien; 03-30-2015 at 5:33 PM.

  11. #41
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    Quote Originally Posted by Mike Henderson View Post
    Julie - this is off topic but you mentioned "load balancing". On an industrial job, does the power company require a level of load balancing across the three phases of a 3 phase system? Or is the single phase portion of the load generally so small that it doesn't matter?

    Mike
    I've never seen the power company worry about load balancing on a residence but I have heard they have complained about it on large jobs. Every drawing that comes out to the field should have had load balancing done by the engineers, but sometimes that doesn't happen or the actual loads don't match the engineer's loads. But in residential, that's never done, at least not that I've ever seen. Usually the installing electrician will do some basic calcs to make sure it's close.

    Quote Originally Posted by Peter Aeschliman View Post
    Julie,

    Any tips on pulling wire through conduit? I.e., do you use any kind of lubrication? I assume you want to pull rather than push, which means using some kind of fishing line- how do you push the fishing line through the conduit?

    I pushed some wire through a 3 foot length of 1/2" conduit yesterday and have to admit, my cursing would've made nuns cry... and that was only 3 feet!

    Thanks,
    Peter
    If you couldn't get through 3 feet of conduit, I'm guessing one of three things was present -
    1. you were trying to push too many wires through or the conduit was already packed
    2. You didn't trim the head and it was too large
    3. You just pushed the wire through without making a head

    Anytime you are pulling wire through conduit, you need to make up a pulling head in such a way as to prevent the leading edge of the wire from catching on anything. The head should be smaller than all the wires when they are trained together. By training I mean they are laying snugly against each other and aren't snaking around one another.

    If you are pulling through a conduit that already has wire in it, you should first look at how the wires enter the pipe and find a spot where there's the most room to start the fish tape. If wires aren't trained when they are being pulled in, they can snake and twist all kinds of ways and make pushing anything through a nightmare. If you start feeding the fish tape or wire and it stops, pull it back out and start at a different spot in the conduit. As a rule, it's always best to have wire pulling lubricant when adding wires to a conduit. Don't use dish soap! Some can harm the insulation.

    I'll need to take some pictures so I can show the steps and what to avoid.

  12. #42
    Great thread. I love conduit bending. It is my craft & it has bought me the tools that allow me to indulge in wood working.

  13. #43
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    Quote Originally Posted by Julie Moriarty View Post
    If you couldn't get through 3 feet of conduit, I'm guessing one of three things was present -
    1. you were trying to push too many wires through or the conduit was already packed
    2. You didn't trim the head and it was too large
    3. You just pushed the wire through without making a head
    Thanks Julie and Phil.

    Yeah, I left out the part about how I was pulling (err, I mean pushing) too much wire through. ;-) It was a straight 3' run of #10 4 wire romex in 1/2" conduit. My understanding is that code allows me to run that length of romex in conduit in my area, but not much more. It's in an unfinished basement for my dryer (had to move it to a new spot to make room for my shop). So it was a fairly extreme situation I guess. I just wanted a little protection on the wall between the box and the joists.

    It just highlighted to me that pulling wire, even when done with separate wire and bigger conduit, is going to be a pain in the butt when the time comes for me to do my whole shop!

  14. #44
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    Quote Originally Posted by Peter Aeschliman View Post
    It just highlighted to me that pulling wire, even when done with separate wire and bigger conduit, is going to be a pain in the butt when the time comes for me to do my whole shop!
    Not at all, Peter. It should go fairly easy if you laid out the conduit with wire pulling in mind. Just don't try to pull in romex!

  15. #45
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    Julie,

    Thank you very much for this post. I've bent conduit for about 50 years and you have taught me a few tips for better ways of doing it than I have been doing all these years. I wasn't aware that they had made a special level for doing this. I have always relied on my old magnetic bullet level and my guestimate for angles other than 45 deg. I'll have to add one of these to my toolbox. I have often used the lines/grid of floor tiles as a guide for my bending whenever I've been working where they are. They make it easy to see bends that aren't perfectly straight and square, especially when doing more complicated combination bends and offsets.

    Charley


    You should consider making this post into a pdf file and available for easy download. It will become a bible for new, as well as older electricians, or wannabes.

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