Electrical conductor types in the NEC

hello everyone hope you're doing well greetings from a cold and snowy salt lake city utah hope you're all having a wonderful day i am having a great day because i you've got mail you've got mail you've got mail [Music] [Music] brad r asks most of my career has been commercial electrical and i have not been exposed to very many cable types could you do a video on the various wire types for example xhhw-2 also known as cross-linked polyethylene rhw-2 urd cable mainly the uses and codes that apply to them thank you for your time you're welcome for my time brad and thank you for your message uh before i forget let me address urd cable um because i will forget if i don't do it right now uh there is no urd that's not a thing uh urd is just a slang term for underground residential distribution uh if you go to the parts store and you say give me some urd what you're going to get is use two all right you're going to get individual conductors plexed together with a optional binder element around them uh and that's going to be their triplex or quadruplex that is urd as use-2 we're going to talk about usb conductors but in case i forget they're also newly added in article 338 in the 2020 code take a look at 338.2 for the definition of uh multi-conductor assembly i think is what it's called 338.2 for the definition 338.100 for some construction specifications so before i forget about urd which again i'm going to forget because there is no urd it's not a thing so with that said let's take a look then at article 310 which of course is where we're going to get the answers to these questions so article 310 conductors for general wiring 310.1 the scope i always like to start with the article scope whenever possible and this was revised in the 2020 edition so it's particularly important that we talk about this um as you know my yellow underground text is showing a code change so article 310 says this this article covers conductors rated 2 000 volts and less including their types insulation markings and capacities and use all right so the change in the 2020 code is twofold number one they reconfigured and and redid article 310 and quite frankly they did a great job with it um article 310 is a much simpler and more user-friendly article than it was in 2017 and previous versions and one of the big reasons for that is that they limited article 310 to just 2000 volts and less now let's just be honest for a minute most electricians really don't get above 2000 volts you know some certainly people do medium voltage but most of us don't so article 310 in previous versions of the code had maybe five pages of actual requirements and then probably 15 pages of tables most of which nobody ever used because they were medium voltage or they were really unusual applications but here's the problem because there were so many tables back to back a lot of people would give up reading article 310 i mean how long do you just keep on looking at tables that nobody uses before you give up and you say well i guess i've read all of article 310 well that was a mistake because there was material in the back of article 310 that was pretty important and nobody saw it so in the 2020 code we rewrote article 310 i say we um let me explain that anytime a good code change happens i say we made that change anytime a bad code change happens i say they made that change so just kind of a wii and they type of a thing so this is one of those changes that we made all right so we limited the scope to 2000 volts and less what do we do with medium voltage conductors and cables well those are now in article 311 so if conductors like these are your cup of tea well great it's in article 311 so this article covers the use installation construction specs and opacities for type mv medium voltage conductors and cable all right so that was kind of a change made in article 310 and 2020 back to 310.1 i want to quickly mention that article 310 does not apply to conductors that are an integral part of equipment such as motors and similar so i don't need to look at these conductors on this ballast to see if they're of a type indicated in 310.4 if they're marked in accordance with 310.8 i think we don't need to be worrying about that that's not conductors that's just equipment so with that said let's jump into 310.4 because that's we're going to answer brad's question 310.4 application and construction of conductors lots of good information here in table 310.104.4 i need to stop saying 310.104. it was 310.104 for you know 50 years now it's 310.4 insulated conductors must comply with table street 10.4 a and b and then there's an informational note and it's worth reading especially if you're in a cold environment like i am there's an informational note that says listen thermal plastic insulation can stiffen at temperatures colder than 14 degrees f and could deform and become damaged when bent during the installation so we want to be careful that we're not installing it in too cold of a temperature thermoplastic like th hhn or thwn those of us that have installed in cold temperatures can attest uh it gets miserable to work with and a lot of times what will happen is the nylon will crack and come off of it now i do want to clarify that that's not the insulation that's just a nylon covering and damage to the nylon is usually okay uh damage to the actual insulation of course is not now i try to cite my sources is it just my opinion when i say the damage to the nylon is okay no i'm not going to go out on the limb like that unless i can back it up this is from one of many manufacturers this one happens to be from cerro wire but if you go to the other manufacturers they're going to say the same thing they have an faq on their page is the nylon jacket on th n for mechanical protection only and their answer to that is quite interesting the function of the nylon jacket on any th-n slash thwn product is twofold first it works with the pvc insulation to provide enhanced resistance to gasoline and oil so that's important if you're installing this stuff at a gas station or refinery somewhere where you need resistance to gasoline and oil you can't break the nylon outer cover if you go to 501 i think it's 501.25 maybe it's 501.125 that talks about gasoline and oil resistance for conductors in class 1 locations so if you need that gasoline and oil resistance then the nylon jacket is really important let's keep reading pvc is already resistant to gasoline oil okay great secondly it provides additional abrasion and damage resistance during installation for the pv insulation on the product the nylon is not intended to provide any electrical insulation for the product if the pvc insulation is not damaged then the electrical integrity of the cable is unchanged even if the nylon is completely removed the pvc insulation is not compromised by contact with water since pvc is moisture resistant so there you go the nylon jacket does two things it gives you gasoline and oil resistance and it protects the product during installation and actually ease uh adds uh it helps in the ease of the installation as well helps it glide through the product a little bit easier so if you break the nylon jacket don't sweat it's not a problem unless you need the gasoline and oil all right let's go ahead and jump into table 310.4a application and insulation 310.4 includes the following it includes conductor temperatures allowable uses coverings and insulation values all right so we're going to talk in generalities here for just a moment okay this does not apply to every single cable under the sun but generally speaking we can say this with with with a reasonable amount of accuracy generally speaking if the wire does not have an h in the insulation marking t-h-h-n t-h-w and if there's no h's then you're probably talking about a 60-degree conductor if there's one h like thw that would be a 75-degree conductor if you have two h's that would be a 90 degree conductor t-h-h-n for example and then if there's a dash 2 suffix xhhw-2 thwn-2use-2 if you have a dash 2 at the end of it that means it's a 90 degree conductor even in a wet location as we're going to find out here in a minute there are conductors where the temperature rating of the conductor changes based on whether you're installing it in a dry location or a wet location so that dash 2 at the end of it can actually really help us out now again this is just speaking generally we're talking about th n rhh xhhw the stuff that we use and install every day if you want to talk to me about you know fep or mtw some of the weird stuff you know these thumb rules don't apply to those but for the the stuff that we installed every day those are kind of the the guidelines for the temperature ratings if we see the letter n at the end of a conductor that means it has a nylon outer cover so t-h-m t-h-w-n so what do we know so far about t-h-h-n well we know there's two h's so we know it's a 90 degree conductor we know there's an n so we know as a nylon outer cover if i see the letter r like rhh or rhw that means it's a thermoset insulation so if i have if i have rhh we know that's a 90 degree conductor with thermoset insulation the letter t means that it's thermoplastic insulation and that's the stuff you don't want to install if it's colder than 14 degrees off by the way you really don't want to install thermoset if it's colder than negative 13 uh f so you don't want to do anything if it's colder than negative 13 degree f it's older than negative 13 degree f you need to be in the truck right so anyway t is thermoplastic insulation so now we know what thhn is thn is what a thermoplastic insulation rated 90 degrees with a nylon outer cover so i can use that around gas and oil you means that it's good for underground so use conductors for example that would be underground or if you have uf or uh let's see uf and uh usc i think are the two that uh that start with the u those are both good for underground if we have the letter w that means we're good for a wet or damp location so thwm we know that's a thermoplastic 75 degree wet location nylon outer jacket and then we have x which is for cross-length polyethylene thermoset so if we have xhhw that's a cross-linked polyethylene but it is a thermoset insulation nonetheless it's uh hh 90 degrees w would mean it's good for a wet location right and if it's xhhw-2 then we know it's a 90-degree conductor in a wet dry or damp location all right so with that in mind let's go ahead and open up the code book together and we're going to look at table three 10.4 and we'll really get to the bottom of this so i'm going to use nfpa link by the way if you're not using nfp8 link man what are you doing it's only 10 bucks a month for a single user and it's uh it's even less i think if it's multiple users and you get access to every single nfpa standard not just the nec and nfpa 70 70e but every single nfpa standard that they make you do a lot of fire pumps and you want a copy of nfpa 20 but you don't want to buy it cool get yourself a copy of nfpa link so nfpalinc.org let's go to 310.4 sorry that's the end of my sales pitch i don't care if you get link i don't make any money off of it but uh for 10 bucks a month it's a steal and you can use it offline now by the way 310.4 let's make that table bigger and hopefully you guys can see that looks like we can so we can scroll down here we have mtw which is like machine tool wiring for a wet location but i want to spend more time on the stuff that we really deal with on a normal installation rhh is something that we might deal with rhh is often used for uh pv solar applications it's also something that uh the conductors will have a dual listing they'll have their product listed as one thing and as rhh or rhw so what do we know about rhh we already talked about it it's thermoset right starts with the letter r has two h's so that's a 90 degree conductor i don't see a w in it though which means it's dry and damp locations only you can buy this stuff in 14 gauge right up to 2000 kc mill it's a moisture resistant flame retardant non-metallic covering if i wanted to put it in a wet location though i would either buy rhw which we know is what thermoset wet location 75 degrees and you can see that right there or i could always buy rhw-2 which is what thermal set 75 degrees what location but the dash 2 remember the dash 2 is 90 degrees even in a wet location so rhw-2 dry and wet location good to go let's see what else we have how about th hhn we know what that is that's heat resistant thermoplastic t-h-n it's a 90-degree conductor it has two h's there's no w though so that means it's only good for dry and damp locations holy smokes so what happens when you install th hhn in an underground conduit remember the inside of a conduit in a wet location is a wet location right 300.5 b tells us that and uh so does 300.9 and so is the definition of uh wet location location commode so can i install thn underground no no absolutely not than underground or outdoors is a violation now does that mean that you've been doing it wrong your whole career and you're going to be burning down the whole town in a couple of years no because when you go to the parts store and you say hey give me a roll of t-h-h-n what are they actually giving you they're not giving you a role of t-h-h-n they're giving you a role of t-h-h-n-t whether you like it or not okay so don't sweat that you're uh using th n incorrectly for the last 30 years t-h-h-w we know what that would be right that would be a thermoplastic 90 degrees wet location 90 degrees in a dry location so let's take a look at that it's thhw which means you can put it in a wet location but in a wet location it's only good for 75 degrees it's good for 90 degrees in a dry location okay interesting well what if i wanted th hhw and i needed the 90 degree location rating and i'm in a wet location well what you'd do is you would get yourself some thwn-2 which we know is 90 degrees in a wet dry or damp location that's because it's a flame retardant moisture and heat resistant thermoplastic you can buy this stuff from 14 gauge up to 1 000 kc mil as we know it's got a nylon jacket or equivalent what do we know about tw we know that's thermoplastic and we know it's good for wet locations but notice that there's no h's so that's only a 60 degree conductor there's not an n at the end either now that doesn't really matter unless you're doing somewhere that requires what gasoline and oil resistance so there you go we've got uf you can buy individual uf conductors usually you buy it in a cable and then we have u-s-e and u-s-e-2 but i think i think maybe my package just got here in the mail my dogs are my uh are my poor man's alarm system so i think the ups guy just got here so hopefully that's my uh peter wright darts practice rings set that i ordered looking forward to playing with those so usc-2 is what it's good for underground use it's service entrance cable dry and wet locations 90 degrees and then last let's take a look at our xhw which is a cross link polyethylene product it is thermoset insulation 2hs means 90 w means wet location and it's going to be the same concept when we scroll down here to xhwn so we have a cross-linked polyethylene thermostat product 1h is only 75 degrees but that dash 2 means it's 90 degrees wet dry or damp the w means wet location the n gives us a nylon outer jacket xhwm-2 is the stuff make no mistake rated 14 gauge up to 1000 you can get xhhw in sizes all the way up to 2000 uh casey mill if for some insane reason you decided you wanted to you know go bigger than 1000 kc mill if you do that video yourself bending it and send it to me i would love to uh to watch you wrestle some of that stuff all right so that is table 310.48 so let's look at this conductor thn slash thwm-2 what do we know about it we know it's thermoplastic we know it's 90 degrees we know we can use it in a wet location at its 90 degree rating and we know it has a nylon outer jacket or equivalent so we can wire up a gas station with it right that's our thwm-2 what do we have here looks like we have some dlo cable i don't remember seeing dlo in table 310.4 and that's because it's not there okay what do i do if i have a conductor that's not in table 310.4 well the answer is simple you don't install it you can't just take a piece of copper wrap some sort of non-conductive material around it and think that the code recognizes it that's not the case only the conductors that are recognized in 310.4 can be used so this is dlo can't install it that's why if you look down a little farther it says rh slash rhw-2 as well so when you see dlo cable and i used to get this question all the time in the area where i inspected we had a couple of decent size industrial facilities and uh sometimes they would call when they actually were you know getting a permit and they would ask they'd say oh my gosh i got some 444 kcmil wire what's the opacity of it and i said well let's let's let's do this in in the right sequence 444kc mill before we figure out the opacity let's figure out what kind of conductor it is and they'd say dll and i'd say oh that's easy you can't install it anything else i can help you with and of course they'd freak and i say all right let's let's keep looking and if it says rhhw-2 then you can put it in now that still begs the question what's the ampacity and until the 2020 code that wasn't addressed it didn't give us any guidance in the 2017 and previous versions of the code and to tell us what to do now in section 310.15 it actually says for opacities that are not indicated in table 310.16 or 310.17 then the ampacity can be interpolated using engineering supervision so get yourself an engineer that can extrapolate the current between 450 and 400 kcmil and figure it out that way while we're on the subject let's talk about a couple of other code articles that are kind of worth mentioning table 402.3 for fixture wire and table 400.4 for chords are very similar to uh to the tables that we just talked about so let's go ahead and open our code back back up and let's go to chapter four we'll start with 402.3 for our fixture wire not too often that we install fixture wire but we do once in a while so it's worth understanding at least what it is and how to use the table if we scroll on down to the most commonly installed types that would be tfn and tffn so tfn is a thermoplastic insulation like you might have guessed and is what nylon jacket perfect f is what fixture wire two f's is what flexible fixture wire so tfn tf fn are your two most common they are rated 90 degrees both so the the h thing you know the h or the two h's doesn't apply to uh fixture wire and then of course if we were to scroll down i've never seen this or if i did i didn't notice we have x f f what do you suppose that would be that would be cross cross-linked polyethylene right poly is that spelled right poly olefin interesting i have never heard the word polyolefin in my life so maybe it's not polyethylene i've always thought it was crosstalk polyethylene ff is going to be what fixture wire that's flexible and then let's go to table 400.4 for our chords scroll on down here and this is where we're going to find the characteristics for flexible chords uh lamp chord type c for example let's keep on scrolling down here ev is electric vehicle cable you might have guessed that one g is portable power cable that's worth knowing about if we keep on scrolling down here we get into our hard service cords and our junior service cords those are the ones with the letter s right for service cord and if we keep on scrolling we've got seo which is what service cord thermoplastic elastomer elastomer elastomer oil resistant there's your s your e and your o s e o w is going to mean the same three things plus what damp and wet locations yeah something else that's worth checking out is the permitted uses of the cord notice how this uh table here says pendant or portable you know if it doesn't say pendant then you can't use it independent application now a lot of the cords are rated for pendant applications but if you were wiring a luminaire or if you had a uh a cord drop you know going to a uh going to like a wood head box with a receptacle you better be using a cord that's rated for pendant use if you're not it's going to be a violation so some little interesting things here in table 400.4 sj is going to be what service junior so junior hard service court not quite as good as service cord if we keep on scrolling all the way down we've got hard surface cord and that is rated for what extra hard usage if you scroll all the way to the right in fact i'm not certain that you can see it here unless i do that so there's your extra hard usage on uh hard service cord s-o-s-o-o-w and there are sections of the code that require a rating of extra hard service if we scroll down here to the last one that i want to talk about that's going to be spt-2 spt-2 is a flat two-wire cord uh well two or three wire usually it's two-wire um kind of a trade name is a is a zip cord so it's like a kind of like lamp cord um so that would be your spt-2 your flat two conductor or three conductor cord and then again we scroll down here and we've got some oddities like vacuum cleaner cord and parallel tinsel cord and things like that so there you go that is your table 400.4 the last table that i want to talk about is going to be table eight in chapter nine that contains information like circular mill resistance and stranding so let's go ahead and take a peek one more time we're going to search it this time and go to table eight we're gonna search all of that and we'll go to table eight let's see here table eight oh where did it go oh see i thought that was hyperlinked my bad struck out on that one let's go to in fact you know what we'll do we'll just do chapter nine table 8 which is conductor properties there we go all right i'm going to make myself disappear so that you can see the whole thing if i have 14 gauge conductors that is 4110 circular mil and that's something that we need to know about in some calculations you can get it in one strand which would call solid of course and you can also get it in stranded which is seven strand so those are your two stranding types gives you the overall area of the conductors and then if we scroll over here to the far right it gives us our dc resistance for both copper and aluminum conductors now aluminum is straightforward enough if you're doing calculations make sure that you're careful about whether you're doing it in thousands of feet or thousands of kilometers very easy mistake to make but what's this business about coated and non-coated copper well uncoated copper is the copper that we all use every day and know and love coated copper is coated with what it's tin so tinned copper is what we're talking about here in the far right hand side as we stroll down to our larger conductors one of the things you'll notice that changes is the number of strands you know if we only had seven strands for a piece of forat that's gonna be pretty tough to work with so once we get to one gauge and larger it's 19 strands once we get to 250 kc mill and larger it's 37 strands once we get to 600 casey mill and larger well find somebody that's bigger and stronger than me to deal with that so with that said i think we made it through our little journey of 310.4 400.4 402.3 and table 8 in chapter 9. i hope you had as good a time as i did and we'll see you on the next video thanks everybody please do be safe be sure to like follow subscribe and ring the bell

Channel: Ryan Jackson

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Length: 28min 3sec (1683 seconds)

Published: Fri Dec 10 2021