How Many Wires Can Fit in Each Hole?
ฝัง
- เผยแพร่เมื่อ 24 เม.ย. 2022
- When roughing in for new residential wall rough, does it really matter how many pieces of NM cable we put into each hole drilled thru the studs? In the latest episode of Electrician U, Dustin answers this question and brings to light some of the code articles associated with it.
🤘⚡️MEMBERSHIP⚡️🤘
JOIN ELECTRICIAN U - become a member and get:
FREE Continuing Education every year
FREE Practice Exams
FREE Monthly Video Courses
FREE Weekly Live Instructor-Led Classes
FREE Monthly Educational Newsletter
Premium Members-Only Content
Private Discord Channel
Monthly Members-Only Discord Chats
Sign up here --- www.electricianu.com/electric...
🎧🎹MUSIC AND VIDEO:🎹🎧
/ descantmv
🎬✍️ART AND ILLUSTRATION:✍️🎬
www.daverussoart.com
The very first thing to mention would be your local AHJ. The Authority Having Jurisdiction. That usually is your local inspector. They have the final say on approving your installation or not, so it makes sense to see what they are requiring, before just going out and doing! Some inspectors like no more than a couple, while some allow you three, etc. The last thing you want to do is rough in an entire house only to find out that the inspector won’t pass your wall rough, and you must do a bunch of rework! Trust me here, its no fun and can be quite aggravating (as well as expensive).
The NEC doesn’t specifically talk about how many wires you can install in a given size hole in a stud. And that also makes sense when you think of how many different sizes of holes you could drill in a stud. What the NEC DOES talk about that is related to the topic is cable bundling. If you were to install a bunch of NM cables together thru the wood studs and tie wrap them every few feet, it may look nice and neat but there are a few issues with an installation like that. The first would be heat dissipation. With so many cables that close together, they cannot dissipate the heat generated by the flow of current in them. This can be a point of contention to some of us. The likelihood of ALL those NM cables being run at FULL CAPACITY at the same time is pretty low, so is the need to dissipate a TON of heat really that important?
The more likely reason the NEC doesn’t allow us to bundle (without derating) is due to capacitive coupling. When you have two conductors run next to one another and an air gap in between them, you have the ability to build up capacitance. Capacitance is the ability of a component or circuit to collect and store energy in the form of an electrical charge. So, the theory here is the more space you provide between those conductors, the more you can reduce the effects of that capacitance. That capacitance CAN impede current flow in the conductors. If you had 10 cables bundled together, with 10 different amounts of current flow running thru them, all that capacitance can have a large adverse effect on the current flow. Table 310.15(C)(1) of the NEC is where we derive the values that we must derate our conductors when we install several of them together in a conduit or thru the wood studs of a wall, or things like that. The NEC doesn’t tell us that we CAN’T install many cables closely together, just that when we do, we may have to adjust our conductors to be able to carry less amperage than standard wire sizes normally allow.
So, in a nutshell, NO, the NEC doesn’t tell us how many conductors we can put in any given size hole in a stud. The larger the hole, the more cables you can fit in there. And the larger the hole, the less chance of you damaging the NM cable when pulling it thru the hole drilled in the studs. Don’t make the hole so small that it takes a truck to pull it in there, but not so big as to damage the studs. In fact, Article 300.4(A)(1) of the NEC tells us that if we drill holes in the studs for NM cable, that we cannot be closer than 1-1/4” to the nearest edge of the wood member, and that if we DO put them closer than that, we must install nail plates to protect the cables from screws, nails, or things like that! Bottom line is to plan your work and install the cables without damaging them.
We hope this sheds some light on the subject. We would love to hear your thoughts on cable bundling, heat dissipation, and capacitance. Leave your comments below in the comment section! Please continue to follow Electrician U and Dustin as we are constantly adding new content for our viewers!
#electrician #electrical #electricity
![[TH] VCT Pacific Stage 2 - Week 3 Day 3 // DFM vs PRX | DRX vs TLN](http://i.ytimg.com/vi/il3Twexat3A/mqdefault.jpg)
Carpenters sometimes call electricians and plumbers termites.
I have "center drilled" houses to run home runs to the panel before. Starting with a 3/4" hole at the far end of the house and increasing it to 1 1/4' and 2' as I got closer to the panel. The inspector was quite impressed with my work and complemented me on how neat and clean my work was.
I had an inspector tell me the limit on the amount of romex in the hole was "There wasn't enough room for thermal expansion". I had to stifle a laugh. In his mind I think he expects copper to expand by orders of magnitude when it gets hot.
It expands exponentially..... just with negative exponents. 😂
Not relevant to this electric issue, but when I learned blacksmithing, I was shocked to learn how important thermal expansion was to the work. I assumed it could be ignored because it would be so small, but not so when dealing with the high temps of smithing. When you heat up steel to a typical (yellow hot) forging temp of around 2000 F, a 1 ft length of steel will expand in length about 1/8". So when we are punching holes in hot metal, the expansion becomes very important to compensate for. If you need two holes 12" apart when cold if we measure when hot we will be 1/8" off. So often we mark the metal when cold to deal with this. Because of the very high temps, the expansion becomes significant and important to understand and workaround.
Of course, with loose wires, they never got hot enough for the expansion to create any effect we need to deal with, at least not in residential wiring. It's all about how heat gets trapped and causes temps to rise more. forcing us to derate the current capacity of the wires,
@@CurtWelch you're right, not relevant, but cool nonetheless. I never thought about how much metal expands and contracts on that scale, I'm usually reminded of it when mile long sections of rail kink in the hot sun because they've expanded so much.
yeah, ANYONE is good enough to be an electrical inspector LOL
I think some of the limitations are because we used to run 14/2-3 (or even smaller) through walls, while today it’s more common to see 12/2-3 run through walls for additional safety and capacity when needed. The margin of safety between 14 and 12 awg wires is significant, and running 12 awg limits the heat, capacitive resistance, inductive resistance, and expansion those wires might otherwise experience with smaller wires. Running 12 awg is like future-proofing the home. I always recommend running 12 awg, as well as running CAT-6 to every room in the house (and 2-4 runs to every possible media location). CAT-6 is useful in so many ways that it just makes sense to run it before the drywall goes up.
Capacitance is not an issue for 60Hz wires. As stated by another commenter, the capacitance between the hot and ground conductors in a Romex cable is greater than the capacitive coupling between arbitrary pairs of Romex cable. The reason for limiting conductors in shared holes in the rules must be some of the other things you mentioned besides the capacitance.
If we assume that Romex has about 20pF per foot, 100' gives about 2000pF, which has a capacitive impedance of about 1 Meg Ohms at 60Hz. That would give about 100 micro-Amps of current flow. If we consider another Romex cable as close as it could be for that same 100' length, the capacitance would probably be ten times less. The result would be insignificant.
Totally screenshotting this!
The capacitance is not in series with the conductor, so it does not impede the current flow in any way. The capacitance is BETWEEN conductors and results in tiny amount of ADDITIONAL current (leakage current). The conductor derating table is there for heat dissipation reasons due to the cables being bundled. Notice that the derating table references ambient temperature, which is a huge hint that they are concerned about temperature rise in the cable.
@@njnear Yes, and the total capacitance is related to total length, so even though there would be a larger capacitance in an exceptionally long run, the capacitance per unit length is only about 20pF (virtually no effect). The resistive losses are also related to unit length, so the heat produced (per unit length) is the key factor. Any time the conductors (and heat) are concentrated into a small area with restricted thermal paths, the temperature rise concern is valid. It is more important for multiple cables in longer enclosed paths because a 2" long hole in a stud may generate more local heat, but the copper conductors will help conduct this heat away from the tight area, spreading the heat out over several more inches, lowering the peak temperature of the conductors (and more importantly, the insulators) in the hole.
Capacitance or inductance is very possible in a 60 hz application. It’s depends on the voltage levels. At normal residential voltage level (ie: 220/120) I will agree it’s not an issue. But, In industrial applications where you have full line voltage (kV) to a switch gear it is a concern that must be keep in mind.
@@sparky_oo1955 Yes, for the power companies with hundreds of miles of transmission lines, they need to be concerned about inductance and capacitance in their designs and controls, but for residential or commercial applications (normal people), the effects at 60Hz can be ignored. Also, the inductance and capacitance don't depend on voltage, but the currents that flow are always Voltage/Impedance.
I would argue that wall insulation has more effect on the temperature of the conductors than bundling does. Wires in open cavity walls can dissipate heat far easier than having a bat of fiberglass insulation or spray-in insulation around them.
100%
Your right, ive had Home runs goin
Threw the same Hole, and the sheathing has turned brown from
Heat, and Yes after insulator does his Foam
You are both right and wrong.
@@stephenballard2560 care to elaborate?
Well that would fall under the ambient temperature adjustments that you should be considering. If you are an electrician, then you should be factoring it with insulation ratings.
2:42 I have seen an electrician get killed from that issue, it was actually inductive coupling. The new wire run wasn't grounded running next to a live 7.2KV 3 phase run, which induced enough voltage and current into the new "dead" cable. He grabbed the cable to work on it, not verifying that there was a ground in place, and was electrocuted. That was preventable for sure. 😢
Yeah saw that happen on transmission lines before too. Literally adjacent towers. But it was enough to induce and kill
That's really sad
Yeah, I think the major issue is inductive coupling, not capacitive. In AC inductive coupling can look an awful lot like capacitive coupling until you realize that the capacitive plate sized of two conductors running in parallel is so tiny that really only noise will transfer. Inductive coupling can transfer significant power. Two conductors run in parallel is a simple transformer with a single winding on both the primary and secondary.
well, yeah. you shouldn't run anything close to a High Voltage cable. there used to be a thing- you could run conductors from different voltage systems in the same raceway, as long as everything was rated for the highest voltage present.
@@larrystuder8543 It's still allowed if the voltages are identified as different, but I don't have the code reference. Usually, it's not a problem since most wire we use is rated for 600 volts. This much higher voltage is naturally more dangerous. I'm not sure what precaution is effective, but it doesn't hurt to ALWAYS test with a non-contact voltage tester.
Like he said, it depends on your local inspector. With 4 conductors in a 1" hole, my inspector
said I could only have 2. --- Drilled a new 3/4" hole and re-ran the conductors. All about getting signed off. ---
While we're on the subject of romex running, can you make a video on techniques to rolling out home runs? I've done it now twice, and it just seems like I'm missing some very simple tricks because it takes me FOREVER. Also, what staples do you use and how do you install them? The ones I've tried are a nuisance to put in, and I always end up smashing my thumb multiple times. Would love a video on BASIC techniques of pulling romex, drilling holes; hammering staples and boxes. Just can't seem to find a groove you know
The best way to hammer the staple in without smashing your thumb is by using the Mr Miagi technique. Gently tap with hammer to start staple. Breathe in, breathe out, swing once, thumb no get squish like grape!
do you mean actually uncoiling the wire? you need some kind of spooling device. for the absolute simplest, make a platform out of some kind of scrap material. make a cone in the middle that the coil of romex will fit over, and hang it from the ceiling joist or truss with some kind of swivel so it turns freely. or if you are going to be doing a lot, there are dozens of spooling devices you can buy.
Use needle nose to hold the staple until you get the movement down. No more hulk smashing.
Use a spinner. The white plastic staples are a lot better than the old type.
Well in Canada, our equivalent of roomex comes on reels already, which I am guessing is not always the case in the US. This means any sturdy rod, pipe or whatever is all one needs. That and a stand for the pipe to rest on.
Thanks again for all u do … it’s incredible how much u share
Great video Dustin keep them coming great information!!!
Thanks for your videos. I'm retired but still fun to watch.
Dang Dustin, you nailed it again. Man I love this show and your truly a mentor of mine. I have been a general contractor for 30+ years and I still find a ton of value in your teachings.
I'm 72 still at it. Great trade to be in. Always something to learn
Thank you for sharing your knowledge.
I wish this channel was around when I was a first year. I've learned so much in just a few of your videos. Thank you, Sir.
Mostly this is where I learn. More clear than the school I’m attending
Hey Swedish electrician here, damn you guys have a easy job. Here in Sweden you have to draw all wires in plastic pipes (when the installation are in walls). But that can also be very useful when you need to change wires/cabels.
It varies. For example, Chicago, IL requires metal conduit in the walls.
@@taylorlightfoot that sucks
@@taylorlightfoot just use MC cable then, no problem.
@@davidsherrill375 those rules have nothing to do with the covering of the conductors in metal - it’s a partnership with the pipe fitters union to have metal conduit and metal pipes. Numerous “union” cities were like that.
Electrical was and in some cases still is “conduit only” with flex only allowed in limited length or conditions.
Thanks for the help.
and the comments are gold too.
THANK YOU 🙏!! Another great video!!
Excellent topic Dustin, thanks bro!
Currently waiting for my coworkers , thanks for being awesome with these videos ! Very nice way to kill time and obtain knowledge 🤟
Me too
@@Attmallard helo
@@Attmallard hello
Agree... I too stick to two cables per 3/4" hole. Occasionally, I have to run three through and just up the hole size to 1". Just makes pulling the cable easier.
Right? Why would you want to fight overstuffed holes to begin with?
Ya at some point it's not practical just dril another hole
@@james10739 And I love getting my money's worth out of my $500 DeWalt hole hog.
@@ericthered9655 that much man I really haven't used it much but I picked up a used Milwaukee hole hawg the smaller on with just 1 speed but it works great but I got it used off eBay for like $120 or something I don't remember but it wasn't near $500
@@james10739 I bought the big flexvolt 60V Max cordless with spare battery. It's really a wonderful drill.
Awesome looking service loops.
I have a common practice of drilling a 3/4 hole, and if another run is needed, drill another hole. You can fit comfortably 3 runs of 12/2 and 14/3, and 4 runs of 14/2. My biggest concern of overcrowding is not the breathing factor, but drywall screws skewering the run! Though nail plates are used for some reason, a lot of people think longer screws are better to hang drywall, or put up siding.....in my own home, I replaced a junky GE Slimline panel with a nice Square D. The original panel had no main cutoff, though it was installed in 1981, and passed inspe tion (?), and when I purposely forced tripped a Slimline breaker the damn breaker did not trip...so I could have just replaced all the breakers, but with that expense, decided a new panel was needed. Anyway, there was a siding nail stuck inside the service conductor leading to the panel from the meter. I replaced that wire bundle, opened the cover and saw the neutral was indeed poked. Yes, could have energized my whole house exterior....anyway, catch your " act" on the next video!
Another great video Dustin .
Good video. Something worth mentioning is the derating requirement in 334.80 should the holes be filled with caulk, foam, etc..
👍Great video as always👍
Thank you
You're awesome. Really enjoy these videos.
Bravo. Master class.
Bundling has absolutely zero negative effect on wires/cables. I have examined thousands of cables that spent their lives being bundled and stuffed through holes. The number of failures or installed of damed were....zero.
I spent decades replacing services in AZ. By the time I retired I had done several thousand. Every service is outdoors here and all the cables enter though a hole in the back. It has been done that way way before my time and continues to this day. Why? Because it is a simple and safe installation.
Fwiw, I always carry 3/4 and 1 inch bits. If I know I need to put anything more than a 12/3 and 12/2 in a hole (6/3 alone or 10-3 with 12/2 etc) I always just use the 1 incher. Makes the pulls so much faster, I feel like it saves my customers money. Same logic for anticipating 2 romex per hole. I only do 3+ if there's weird framing that only gives me a single path, but again in those spots I use a 1 inch and ream it if it needs it.
Thanks for sharing 👍🏼
an independent lab ran testing on how many wires can be jammed in a hole without overheating them, so they put various numbers of cables in a hole, foamed the hole, like insulators now always do, and their determination was that you pretty much couldn't exceed 3 cables before you started overheating wires. and capacitance between wires? not a thing I've ever heard of. induced voltage, yes. never capacitance.
and if capacitance is the issue in the wire bundling charts, why is ambient temperature a factor?
You are right, capacitance would be so low with 60 cycle, 240v lines as to be difficult to measure. Even inductance would cancel out as cables tend to twist over distance.
Have the sauce for the study/test?
@@Merescat my code update instructor about 14 years ago.
@@kenbrown2808 No way to verify. I wanted to read it.
@@Merescat sorry. I don't maintain a library for other people. it's not in my scope of practice.
Good point.
Thank you.
You make a good point, it's not all about heat. I assumed inductive effects were more prominent, but as you say there is a parallel capacitive effect as well. I'm guessing this could play havoc with the charge on ground wires, and maybe even cause nuisance tripping of AFCI's.
I doubt AFCIs would trip, they're looking for the high frequency characteristics of arcing, and need to ignore the line frequency as it is omnipresent. The more capacitance you have, the lower the resonant frequency will be..
As usual excellent video. . A happy inspector is an easier day for any electrician. Give those conductors some space .
AFAIK, the heat thing is about insulated walls. With the 2020 NEC requiring GFCIs for almost everything, you may want to limit bundling so coupling between cables doesn't cause nuisance trips.
I have scene more and more tract homes using cable stackers and mailing blocks of wood and separating and neatly stapling the wire 1 or 2 or even 3 on top. Looks neater. Nice to see some better quality work. And I have scene bundled wire that was way to hot. Almost to much to touch without gloves. In both commercial and residential work.
Good video. I didn’t hear you mention if the borings are thermally insulated or not. When it comes to quantity of cables in a hole, that plays a big factor. While I agree that most residential/ commercial installs using romex won’t see more than a few amps, you still need to derate them accordingly. The code is clear on that - 334.80. Curious if you see it another way
I love your love for “crazy people” ;)
Couple years ago, I ran a wood screw into a stud for a shelf bracket…pop went breaker
Opened the wall to find the screw went directly thru the hole, thru the Romex….
No slack to fix it with a wire nut, so I used a crimp butt connector, after crimping I soldered the connector to be safe and covered with heat shrink.
A perfect example of why nail guards are important.
I like it when you explane code. Look at your table, why would you have to "adjust for ambient temperature" if it has to do with capacitance? Not to argue but a very large effect of transmission lines is the inductance of a 20 mile peace of wire. Yes if you place two 20 mile long wires next to each other you can have a lot of inductive coupling.
310.15(B)(3)(a) provides a clear definition of multiple cables in a “bundle”. As a general rule, I stick to 3 which derates the conductors by 80%. This allows for other adjustments that might be applied in addition to bundling such as ambient temperature. Thanks for the video.
Well if it’s more than 12 inches hole, conduit then you have to derrate. But for a hole that small you don’t need to derrate at all(12 length
When I saw the 3 Recepticals, "More Cow Bell" came to mind(Wlll Farrell, SNL)Good Video
When I Drill holes, I like to drill around a 45 angle to reduce the sharp turn.
I do it with Smurff as well. Some helpers won't, I refuse to pull through, they can. Nothing Negative about it, Less Smurf(ENT), Less Wire
you can also use this as a reference for anything that uses a bunch of electrical wires since this is a major problem in major audio setups and intricate pc setups, when cross talk or noise is present it can become a major pain to figure out where its coming from so best to set up in such a way where this just cant happen.
Good Information.
Awesome video, thanks for the great content! Do you have any tips on securing cable in rework situations, like adding 1 gang boxes to an existing residence, and it's supposed to be secured to the nearby stud, but is impractical to nail in due to drywall in the way?
I believe the code says you don't have to staple in that scenario because it would be impractical to.
I think there is a reason this is not addressed in code because there is no problem with the wires in close proximity. The effects of capacitance at 60 Hz is virtually nill. However, high frequency noise often created by power supplies and brushes can be coupled more easily. This is still not typically a problem as these emissions are regulated. Heat is a mild concern, but as you stated total current in a group of wires of a residence is typically very low and further 12 gauge wire is extremely conservatively protected.
I have worked in a data center environment. Heat in residential isn't likely to be an issue unless the runs involved have heavy use or as others pointed out, insulation. In bundles in a data center, they tend to be running full tilt. The capacitive and inductive effects also tend to cancel out and are more of an issue with interference between sensitive systems. We use ferrites where that is a concern but generally the bus strips already handle that. Ferrites and capacitors are used to filter noise from a/c systems. Bus strips filter noise to a rack. But back to the original point, heat is the limiting factor for bundles. In a data center you even have engineered runs with integral cooling. But this is industrial not residential.
NEAT and WORKMANLIKE manner... that's the goal! Your work practices dictate installing a safe install for the end user.
Could you do a video on various staple? Lengths, types etc.?
Appreciate your show and information. Have a ?. Although not bundled, would it not be the same if the wires are tight because of the number of wires?
Great video 👍👍 I truly agree with you! Keep pumping those videos out you're an awesome teacher!
Thanks!
I ran into this when I was fixing the wiring in my home. I killed the circuit and then went to work on the outlet and was shocked by the white wire. I was surprised and read the voltage from it. It was about 2 volts dc and quickly went to 0. As a tech who works with capacitors daily recognised this as the white wire getting a charge built on it. Not only is the Capacitve a reality but also Inductance can play a role too.
You probably got shocked from the neutral wire because it was part of a 3 wire circuit and the other circuit was still on and it was sending voltage back on the neutral. Always put a 2 pole breaker on circuits that are sharing a neutral
@@ryanm2084 no, that is what surprised me. it was a singe line. the shock was mor like a large static shock, maybe it was, but in 30 years of wiring it is the first it happened. i investigated and found bundles of wires running together. I put it down to an inductive transformer effect
I work in UT, typically use a 7/8" Bosch bit and my master electrician says he doesn't want to see more than three wires per hole.
Same
After a solid year of trying to find an answer to this question. Thank you.
You sir, are a saint. Thank you for taking the time to explain in detail the why’s of everything electrical. I can’t count the many times this has informed or helped me on my daily job as a solar electrician.. coming from residential they’re were a lot of commercial-grade codes or utility code I was unaware of.
I appreciate you since this is the best way I go about not forgetting. it’s just my learning style. It’s gotta be showed and explained to me, can’t always just read from a book 🤣
The NEC codes are 310.15(B)(3)(a) and 310.15(B)(16). Up 9 currect carrying conductors. Don't forget to check with your local codes as well.
Great insight by the so called NERDS : ) Outstanding!!
Well said.
Question: getting ready to wire a shop - Better to use Romex or single wires? Your opinion?
As an electrical engineering STUDENT I would say the capacitance would be really low... however the inductance could pose a problem if enough cables are grouped together while all being used... they could possibly induce a current in a nearby metal object, possibly hanging or up against the wall and cause a shock to someone who touches it, it could cause the nearby object to heat up from the induced current or cause electrical items nearby to act faulty to name a few... this happens to vehicles as well where sensor wires in a motor are too close to alternator wires or alternating current wires and start acting erratic and throw codes or those sensors (I'm also a mechanic 😅)
Comparing your terminology to mine is fun. My expertise is in electronic design, not electrician. To me a "conductor" is only a single current carrying element. This includes not only wires, but also individual traces on a printed circuit board. A bundle of wires held together with an external jacket (for example romex or NM wire) is always called a cable. A bundle of wires held together in intervals (with, for example zip-ties) is a bundle, more specifically a wire bundle. A bundle of cables held together in intervals is also a bundle, more specifically a cable bundle. You keep referring to a single segment of romex as a conductor and it keeps sounding "wrong" to my ears, but is probably just a jargon difference between two similar looking (from the outside layperson) industries. This example of jargon differences (and my lack of training on electrical code) is why I'll never claim to be an electrician.
Keep up the good videos. I'm learning a lot of useful information as a new home owner.
Your use is actually correct for electrician jargon also. NM is a cable, inside it are conductors. You terminate the conductors after all, not the cables. That's certainly how the NEC uses "conductor". But you do also hear electricians say conductor to refer to cables. But then again, those same electricians also just say wire to refer to cables which is actually really annoying when it's completely unclear sometimes what someone is looking for. Oh, you need 12 AWG wire, yes I have some right here for you. What's that, you're looking for 12/2 MC actually? Maybe you should have said that instead of asking for "wire".
What is your opinion / the legal stance from NEC on combed twisted bundles?
I would raise two points. First, capacitive leakage causes some heating. Second, you should wiring not for average use, but for the worst case, because it only takes once for the house to burn down.
Your "heat not an issue" argument works fine in typical inside walls, but it's worth considering in outside walls that are insulated. Many years ago, when I was in college, I worked at the local electric utility, and one of the things they asked me to do was to test various types of insulation and their effects on wires. We built a 4-segment wall, ran several conductors through it (14-2 WG Romex, 12-2 Romex, 12 AWG in conduit, 14 AWG in conduit, 14 AWG post and knob) through it, insulated the various sections with different insulating materials (none, fiberglass, cellulose, foam), installed thermocouples to measure the temperatures, and then ran each circuit at various increasing current levels. When we got to 20 amps on the 14-2 Romex circuit (yes, that exceeds NEC but can be a common mistake if 14-2 is connected to a 20A circuit breaker; the utility was aware that some service/panel upgrades used 20A breakers connected to 12 AWG wire at the panel that then connected to existing 14 AWG wire elsewhere in the house), the wall started smoking and caught fire after just 5 minutes of continuous load. The fire started in the foam section, then spread to the cellulose. Needless to say, the test was quickly terminated. The test results were shared with several organizations, and led to some of the electrical and building and insulation code changes we see today.
There is a relationship between induction and capacitance first discovered in parallel open wire telephone lines were they had to use pole changers and induction coils to re balance the 600 Ohm line. "Parallel induction" induction heating" Parallax I think is a more reasonable explanation of why we shouldn't bundle, now off the Golden Tower of theory in cases it probably make no difference like you say Justin.
Yeah, capaci-tive/tance coupling is an effect of induction, right? Works best on parallel conductors. Back in the day, we were taught to take the cat5 perpendicular across power cables.
Please explain what parallel induction heating is and how it would apply in this case. I never heard of it. Induction in an air core, no coiled wire at 60 Hz is negligble.
Hi fire block foam requirements for wiring through drilled holes?
And what is bigger hole we can drilled in 2x4?
Thank you don't know.. you my teacher for electrical codes here in California have a nice day!
Huge tip. Flip your drilling direction every 2 or 3 studs and the wire will pull much easier.
I’ll have to try this. Thanks for the tip!
can you elaborate on how/why this works?
@@AndrewBrowner The holes are not straight. Switching directions averages the angles out so the wire has less friction. Try it. The difference is obvious.
Good to know!
You’re right, the typical home uses do not generate much heat, but you can’t bet on them being low all of the time.
Shielding has little to do with capacitance. The biggest issue I see is drilling too big a hole and weakening the structure.
Overall, a good summary.
Yes you don't want to weaken the structure. But what weakens the structure more two small holes or one big hole?
Heat dissipation is a real thing. Saw someone once that had a window a/c running on a 100ft extension cord wound on one of those round orange holders. The inner wraps had been melted to a single mass of plastic
The way it was explained to me by one of the engineers in a company I worked for the heat and capacitance could adversely effect arc fault breakers. We were limited to 3 14-2 or 2 12-2 to a 7/8" hole and no sharp,creased bends and staples just holding the jacket.
I've never had that affect arc fault breakers and I usually run 3 wires per hole
If the bend in the romex is too sharp it's actually a code violation
It doesn’t look like you do burn loops on your receptacles or lights. Is there a reason for that, or do you just leave slack in the box for future use if needed?
I use to work for a telecom company. I can tell you right now that the sheathing on shielded anything doesn’t do crap unless it’s bonded and grounded properly. If you get out in the sticks, especially aerial plant, inductance will light you up. Been there, done that.
Especially C wire that wasn't twisted when installed, had a co worker yell when he grabbed ends.
How do you guys handle the "embedded in thermal insulation"... without maintaining spacing in NEC 314. That usually limits us here to about 8 CCC per hole before derating would be required, like four pieces of 12-2 NM per hole. 🧐
The other factor which will not be in your electrical code, but like ours will be in construction code is the size of hole you can make and how close to each other. Especially with load bearing walls like external walls.
Should outlets installed have the ground hole up or down when installing??
I am building an ICF home where I will be using a hot knife to cope out foam for a wire chase. Any advice?
how about if the connect plug in heaters to one of two of those circuits in the middle of that bundle and heat cannot be dissipated? where those heaters gonna be on all night long.
If I need to run perhaps 9 sets of 12/2 in parallel, how far do I need to space out the sets of ~3 per hole? Is 6" spacing sufficient? I remember seeing somewhere in code that appeared to require a yet-larger spacing, but I can't put a hand to that reference. Talking about standard 120v / 15A single phase lines.
A hole width between holes is sufficient.
This was never covered in any electrical class I've ever had. Thanks.
Yes, I'm very open to more training.
Can you make a video on what can happen if you leave conductors damaged? Say you accidentally nicked outside jacket with your drill, or when pulling you stripped outside jacket etc..
Question! What type of recessed light can I add to a ceiling that has blown insulation in it?
My house is 123 yrs old and has been rewired twice. The original was knob and tube, most likely done in the early 1900's a good decade after the house was built.
Then, probably in the 40's or 50's, rag wire. About 6 years ago, that was updated with 14/2 (with the exception of one circuit.) And, this should piss you all off... on 20 amp breakers. Additionally, 4 bedrooms and a bathroom upstairs are running on one 20 amp breaker. Keep in mind that this was done by a licensed local electrician. I'm trying to find out who that f@#$er is. But the previous owner, who I know well, will not tell me who. She's afraid of getting sued.
The kitchen is on one 20 amp breaker, again with 14/2 the rest of the downstairs is also on one 20 amp circuit with 14/2. Insane.
The house is a electricians dream with a basement and huge attic and a nice run from basement all the way to attic. Real easy access to everything and, obviously, easy wire pulls.
My thought is, why? The crew that did that shit job would litterally have had to work harder to do such a crapy job vs doing it right.
Now, I'm not a professional electrician. My experience was a electricians helper when I was taking am electronics course in vocational school in Ohio. The comapny i was working for did residential and commercial and I learned a lot. In new/rewire construction, every room got 20 amp service and was a home run to the panel, the kitchen 2 20 amp circuits.
Am i wrong to be pissed off about this? Also, I'm about to run 5 12/2 cables from the basement to the attic to take care of the second floor rooms.
Am I hearing this right? In that i don't have to worry about induced voltage from one circuit to another?
What's with the extension cord pulled through framing members like NM cable?
I agree with this. I always do 2-3 wires per 7/8 hole if it’s 14/2 almost always 2 per hole for 12/2
I think the biggest concern is if the hole is large enough, then it should be protected by a nail plate. Also, if it's too large, construction code might require to reinforce the stub for structural reasons.
It's the distance to the drywall side that counts; which also leads to a max size for a given 2by size (1" hole in a 2by4 ?)
@@wim0104 For structural stuff like load-bearing walls, you want to keep holes near the center-line as it is the outside that contributes most to stiffness.
In the Australian code we have derating factors for bundling conductors together , we also have derating factors for cables installed where insulation could be present. Also the way cables are installed within a insulation area effects how much the cables are derated. .
The U.S has derating also. But really only once you hit 24" etc. No derating through a bunch of 1.5" studs unless they are all together.
@@sapreaper yes we don't derate for stud hole bunching , more for cable trays and enclosures . We also have to bunch cables in certain configurations when running on cable ladders three are allowed bunched then a set distance to the next bunch it's a pain but looks good if done correctly.
Omg it's such an breath of fresh air bro to see someone not try and overcompljcate these codes and try and act like they're some sort of electrical guru : /
Is capacitive coupling the same as induced voltage?
Now that a lot of IOT Devices are using neutral lines as data lines, over packing conduit can cause cross talk and em interference. Too many together can also generate their own radio fields that can screw with wifi, Bluetooth and in some older homes sensitive hardware on unshielded devices
I really enjoy your channel! You are truly professional and I’m always learning something new from you. Thanks for sharing!
Would you or someone be able to help me out with explaining hole fill with a fire wall and fire caulking. At some point I seen the code saying no more than 4 current carrying conductors but can't remeber where or how it all applys
The most I’ve seen is 3 and that was impressive
What is that orange cable with a black stripe?
Can you put 2 12-2 wires in a 1/2" hole in a stud? Great vid.
Here's a question re THHN, not really the romex shown here - is the outer clear plastic sheathing just an expendable layer, expected to be damaged during a pull, or is it actually part of the functionality of the wire?
Can we run 4 numbers of #4 AWG THHN copper wires (60amp breaker) to carry 220v through single joist holes across unfinished basement to ev charging station in garage.
Can we put 3 nm-b cables under one 3/4" staple ? we can not put them flat to each other so at least one of them need to be on top of the other 2 - is that allowed ? can you give code reference? because code NEC Code 310.15(B)(3)(a) says you are allowed 3 conductors - can you confirm?
It's been a few years since trade school where we learned a lot of theory but hear me out😄 I thought that having the neutral ran with the hot(or the 2 hots on a 240) kept the load balanced so inductance shouldn't be an issue with others wires near by. Any thoughts? I really like learning and refreshing info from your videos and these comments, thank you!
Current in a wire creates a magnetic field around the wire. The return current in the neutral creates an equal and opposite field which exactly cancels the first. Well not exactly because the two current carrying wires in Romex do not occupy the same physical space but they are very close to each other and the field remaining is very very small. Not true for knob and tube where the wires are separate. Also a big problem in conduit if the two current carrying wires are in different conduits. You can get serious inductive heating if so.
The capacitive effect drops off very rapidly with distance and is negligible with Romex. Anything more than a few thousands of an inch of separation pretty much ends any capacitive effect at low frequencies. Capacitors are made with 2 large flat surfaces like metal foil with an ultra thin insulator between them, rolled up and put in a can. Network and audio cables are sheathed with grounded foil because they are very low voltage signals that do not tolerate electrical noise that can be picked up from very high frequency electricity like fluorescent tubes or electronic dimmers.
My opinion is the exactly opposite to this video. Bundling rules are all about heat dissipation. I agree most wires in residential carry little current most of the time. But the code is all about houses burning down and if your house doesn't burn down MOST of the time, it only burns down occasionally, that is not good enough. Romex carrying rated load will approach 70 deg C on the wire after 5 minutes in free air. Worse in a wooden hole foamed in. Bundling them together could easily reach the 90 deg C insulation rating even if only one is at full load.
Here's an example. You have a space heater plugged in by your TV and electronics on the same circuit so you are running close to 15 Amp rated load. No problem, the thermal circuit in the breaker will never trip. Unfortunately for you, a different cable in the same bundle experiences a dead short when someone plugs in a faulty appliance. Now you've got 1500 amps ( #12=1.6 ohms/1000 ft, say 50 feet of wire @ 120v) but it's only for about 20 mSec or so before the magnetic circuit in the breaker trips. I would guess, seeing how cutting a live #12 Romex will vaporize enough of the metal in my cutters that I need another pair of cutters, this is going to be a problem and at least melt the insulation in some of the Romex.
@@JamesAllen-tj5nu well said good sir had no idea the wires in free air could heat up so much and quickly on rated load.
@@JamesAllen-tj5nu good insight. Would be great if someone could run the scenario as an experiment. See how much it takes before a #12 or #10 give out and melt some insulation. I can see it happening but having solid evidence changes the entire argument