Wire and cable bending radius requirements

[@Roommate625]

Love seeing new videos. Thank you Ryan for your time sharing and educating!

[@Wolfgang-et7vz]

This channel is incredibly useful, can’t wait to watch all of your videos

[@ktprealestate8805]

Excellent clarification Ryan. I’m glad that I wasn’t the only one to shake his head when trying to understand this section of the Code. Thank you.

[@Squay313]

good breakdown, something that no one talks about but can really screw you. usually comes down to whether the inspector wants to ruin your day or not.

[@MasterTheNEC]

Greetings Ryan - Love the video like always my friend. Just figured I would comment on the maintained bending radii aspect for Wire and Cable manufacturers. We maintain the "diameter" as expressed will depend on how the installer bends the cable assembly. In a flat cable, there are many who will bend it on the flat "long" side or the short side so from our perspective you would use the value depending on how you actually bend the cable assembly. As you eloquently explained, if it was round configuration cable then it becomes moot as it only becomes an issue with flat cable assemblies. Keep up the great work fella.....Stay Safe! (Sorry Grammar Edits - My Trolls love my grammar)

[@MasterTheNEC]

I also should clarify fella - From our (not all manufacturers, just speaking for one that I am associated with) we believe, and not part of any listing mind you, that when bending on the short side you would use the LONG side value. When bending on the long side you would use the Short Side value. Again, nothing demands this as again we will say as long as you do not damage it lets your specific installation be your guide. However, that is how we would tackle the ambiguity of the NEC position on maintained bending radii if we provide any guidance to the installers. Our logic in C & S is that there is more potential for insulation elongation with short side bend than a long side bend, if that makes sense. Hope that helps explain it from at least one manufacturers perspective.

[@RyanJacksonElectrical]

I totally agree, unfortunately it appears that CMP 7 doesn't. They will require the large dimension to be used in the 2023 (barring a CAM or SC appeal). Frustrating!

[@MasterTheNEC]

Oh frustrating indeed.....and always makes me wonder why I do it. But alas....we press on.

[@MasterTheNEC]

@@RyanJacksonElectrical I can tell you why they choose the long dimension value, as I am sure you already know. That affords the manufacturer the greatest value (radii) and reduces the potential for damage to the cable assembly by having an increased radius on the bend for the cable assembly. As usual, the normal conservatives approach if you will.

[@ericisnominal]

Can you do a video on Ground Bushings. Everyone I ask has a different answer for when and where they use them. And I can’t find a clear answer in the code book. Thank you, really enjoy your content. Fun to see pictures and examples from here in Utah where I live

[@RyanJacksonElectrical]

I'll add that to my to-do list

[@JacobYoces]

I 2nd this request

[@felixsandoval486]

Good video as always Ryan. Clear, precise, practical.

[@jamesfroeschnerii8748]

Thanks!

[@RyanJacksonElectrical]

I can't beleive I didn't see this until now. Thank you so much for that, it is very kind of you!

[@ronaldramirez3256]

Wow so easy to picture with a ball’s diameter. Thank you so much!

[@ronaldkovacs7080]

I know this is off topic but I would like to ask the following: At 4:17 we see more than one cable running through a single hole in a joist. does that require the conductors to be de rated?

[@clydenakashima7393]

I have question on the SE cable you shown in the video. So if I have my panel is above where the cable is coming in do I need to place a nail plate on the stud where I am securing the cable too. I live where the the exterior walls are framed with 2x4; so if I mount the meter base on the exterior wall I can't run the wire through the wall up the between the studs into the ceiling to my panel inside the house. Because I won't have the correct bend radius on the cable.

[@RyanJacksonElectrical]

Correct. See 300.4(A) and 300.4(D).

[@danfrias3714]

Can you make a video on cross section of a wire way/pull box?thank you Jack.

[@Jason-ns4qy]

At 5:48 did you mean to say the length of the cable instead of the width. I am confused and am trying to figure out which side of the cable is which. I know we think of length as in the how far the cable is going, but wouldn't it technically be height. I don't know, maybe I'm getting really hung up on the math here. According to the chart would 14/2 romex wouldn't .17 inch width and .39 inch length. Again, I know when people usually refer to length they mean how far the cable is running (like 12 feet of cable), but I thought that math would be the height. Height is the amount if held from the ground up. Length is the longer side. Width is the shorter side.

[@kyle8442]

It's listing the cross-sectional measurements, so there are only 2 dimensions in that case, not 3d. A flat circle/ellipse

[@luckyhiker3434]

Ryan, I would say that if the sheath is removed from a 12-2 NM conductor you would use the diameter of the individual wires. Right? This requirement makes it difficult when setting multiple wires in a jbox. I have seen wires packed into a box and by calculation they met the box fill requirements but minimum bending was very questionable!

[@stringlarson1247]

The thing with NM is that the outer sheathing is very soft and is easy to make it round when working with it. The inner THHN conductors will slide over each other. This gives an easy way to picture the diameter. I'm not suggesting one twists the cable, just that I've run into it when working with that crap. I prefer emt, plus in Chicago/Cook County, it's not allowed :)

[@cheyennea4884]

Wow, I'm a visual person and this just blew my mind. I am always trying to visualize this.

[@buckhunter4413]

Awesome glad to see some content! When installing service entrance conductors say for a 800 amp service can you use parallel 500 rated 760 amps or would it be best to install parallel 600 for the full 800 well 840 amp conductors. I'm just a apprentice needing a little input. Nothing pretaining to work just info. Ik that 83% of 800 amps is 660 amps or so and the load would likely never exceed 83% but would it be best to size over your ocpd? Or could you use the parallel 500 rated 760 amps in the 75°C?

[@RyanJacksonElectrical]

You can use parallel 500s, provided the calculated in 760A or less.

[@user-ln7of9gs4s]

Ryan, awesome video. If the wire kinks 180 degrees during unraveling or install, and you remove the bend, is the wire still good to use? Thanks.

[@davidaengelhart]

Good explanation. Thank you. Not that it is typical, but it would seem that if the bend is with the long dimension of a flat cable (in lieu of the short dimension as demonstrated), the bending radius would be 5X the long dimension of the cable and not the short dimension.

[@rupe53]

Good point. Where this might be common is on the outside of a home running SE cable from the weather head to the meter pan. Since the clamps are generally made for fastening the cable flat, you'd need to consider the sideways bend if it's not a straight run.

[@danielmcdougle6925]

I think the code specifically stats that for flat cables the larger of the 2 dimensions is the one we use regardless of how its being bent

[@rupe53]

@@danielmcdougle6925 ... if that was the case then we'd never see SE cable in a wall cavity, yet we do see service cable going into homes that are bent at the sill board or going straight out the back of a meter pan.

[@davidaengelhart]

@@danielmcdougle6925 334.24 Bending Radius. Bends in Types NM, NMC, and NMS cable shall be so made that the cable will not be damaged. The radius of the curve of the inner edge of any bend during or after installation shall not be less than fve times the diameter of the cable.

[@davidaengelhart]

338.24 Bending Radius. Bends in Types USE and SE cable shall be so made that the cable will not be damaged. The radius of the curve of the inner edge of any bend, during or after installation, shall not be less than five times the diameter of the cable.

[@ecstrawn6603]

good stuff, your contributions are invaluable TY

[@jaredhouston4223]

You have really made this clear for me. I am on a job where the inspector wanted our foreman to change the 4/11s to a larger box size because he knew the radius was very tight. However, this was a change for THHN 4 gauge and not for cable. Would you have made this change? 1inch pipe feeding into a 4/11box with another 1inch pipe 90 degrees to the A/C unit with 3 conductors. Thankyou for the great content, glad to see this video.

[@RyanJacksonElectrical]

I would yell the inspector that I needed a change order signed. Somebody needs to pay for it.

[@jaredhouston4223]

​@@RyanJacksonElectricalWould you please make some content on this subject. Many apprentices including myself are totaling in the dark about these types of conversations that happen with foremen and inspectors.

[@RyanJacksonElectrical]

@@jaredhouston4223 I'll put it on my to-do list.

[@jaredhouston4223]

@@RyanJacksonElectrical 🙌

[@shawncorrigan7514]

The latest version of the NEC added "For flat cables, the major diameter dimension of the cable shall be used to determine the bending radius.". So you cannot use the thickness in any scenario regardless of the way it is bent.

[@RyanJacksonElectrical]

Correct. I tried to stop them from doing it because it was a terrible change, but my public comment didn't help. They are fixing it in the 2026 NEC, however.

[@shawncorrigan7514]

@@RyanJacksonElectrical Interesting. So my state doesn't adopt the 2023 version of NEC until 2025. Since the current version has ambiguity, and the next version clarifies the ambiguity, do you think that an inspector would still interpret the current version with the clarification that the new version has?

[@RyanJacksonElectrical]

@@shawncorrigan7514 Hard to say. I can tell you that in my home state (Utah) we amended the problematic language and have incorporated the 2026 revision. At least, that is the recommendation I am making as the Chairman of the Electrical Advisory Committee next week when we discuss the issue.

[@AaronSchmid1]

Love this Ryan. Thank you!

[@MrKen59]

Love the ball examples 😃. Is the calculation the same with MC? You need a ball example for that too. Thank you.

[@stringlarson1247]

MC will let you know if you're pushing it. If you take 3/8" MC and make a 90-degree bend, it's going to require way too much force to get much tighter than about a 3" radius by hand, and it's not specd to be any less than 2.625" (7 * .375).

[@MrKen59]

@@stringlarson1247 I agree, MC by its nature won’t let you push a bend without destabilizing the joints. Thank you for your explanation.

[@bloodwrage]

Great visual with the golf ball

[@clydenakashima7393]

Thank you very much for clearing that up.

[@gtrob1]

Awesome explanation. You happen to have a pdf of that cheat sheet 😂?

[@chadgerman8173]

Another awesome video!!

[@ronbonick4265]

hey Rtan Hope youre staying warm bro Thanks for the vid

[@lesterwatson8519]

Great practical information. Thanks

[@davidsullivan7739]

This was very helpful. Thank you!

[@bahmannosratollah7017]

Thank you for, great explanation.

[@ronaldramirez3256]

“Golfball”… inspector’s new tool! Thanks Ryan Jackson… LOL.

[@kangaroogod]

Great video and visual aid

[@fayiznalu8411]

That was brilliant. Thanks 👍

[@appamtnculture1302]

Thank you for this information.

[@matthewkerssen5265]

awesome vid Ryan

[@TAQWALEARNING]

Helpful discussion

[@davidjackson4112]

Thanks Ryan!

[@davidjackson4112]

Ryan, when I was wiring Schweitzer Relay using sis 14 gauge wire I would use an 1- 1/2 “ * 8” long aluminum rod. This is what I used to accomplishment my smooth radius for my sis wire.

[@无党派人士-l4p]

Liked and subscribed😀

[@MrOpinionCantSignIn]

Understanding the radius was easy for me . What I do not understand is how 12/2 is thinner than 14/2 per your tables

[@RyanJacksonElectrical]

I had the same issue, but I took the numbers straight from the manufacturer.

[@codydouglass242]

Awesome

[@koarivera9151]

Hope this helps me pass my exam today

[@RyanJacksonElectrical]

Me too! Good luck.

[@philgonzales5310]

The basket ball radius is really big, especially when you put it up to a 2x6 wall, difficult to understand

[@rupe53]

Think of it this way: The basketball is roughly 10" in diameter so only 5" radius. The 2x6 wall is just under 6" so a 90 degree bend is allowed within the cavity. To do this in a 2x4 wall you'd need to use a flat style SE cable because it has a smaller dimension.

[@TannerEskew]

This is probably the most over looked part of the code, I’ve seen some tight bends in some residential new construction

[@mattimus8250]

Thanks👍