Won't These Melt?!? 15amp Receptacles on 20 amp Circuits!!!

why the hell do people put 15 amp  receptacles on 20 amp circuits   all right as an electrician a lot of  times you are going to come across   melted receptacles where a breaker didn't trip  but a receptacle melted at a wall usually this   is going to be around Christmas time or you know  sometime when it's cold and people are plugging a   whole bunch of space heaters in and they're over  utilizing power at a very specific receptacle   how this happens is most of the time people are  putting 15 amp receptacles into brand new houses   because code allows us to do that but they'll  still put 20 amp circuits meaning there's a   20 amp breaker at the panel there's wire that's  number 12 it's rated for 20 amps so it can carry   that much current through it but then you'll  have 15 amp receptacles installed everywhere and   it's like why would we do that why would we  say that we could run 15 amps worth of current   through something or we could run maybe 18 amps  of current through something and the breaker   is never going to trip but that receptacle  over time is not going to handle that and   it's actually going to heat up and start melting  why would we allow that why would we allow that   code that's why code so let's break into the code  210.21 this is the 2020 national electrical code   under 2 10.21 b specifically it covers receptacles  so b1 says a single receptacle on an individual   branch circuit a single receptacle installed on  an individual branch circuit shall have an ampere   rating not less than that of the branch circuit  so that means a single receptacle has to be 20   amps if it's on a 20 amp circuit so there's no  problem there there's no question about that   but then we go down to b3 where it says receptacle  ratings and it says we're connected to a branch   circuit supplying two or more receptacles or  outlets receptacle ratings shall conform with   the values listed in table 210.21 b3 so if we look  at table 210.21 b3 receptacle ratings for various   size circuits on the left hand side it's got a  whole bunch of circuit ratings and amperes on the   right side it's got receptacle ratings so circuit  rating again we're talking about the actual   uh rating of that circuit which is usually  talking about the over current device the   breaker so if we have a let's say 20 amp circuit  rating we have a 20 amp breaker 20 amp wire in the   wall you notice it says the receptacle rating  that's allowed is either 15 or 20 amps why why why not just put 20 amps so if you think about  uh a service like an electrical service most of   the time we'll have like a 200 amp service on  a house but if you ever take your ammeter and   actually clamp onto the conductors you might  have like 20 amps flowing at any time the   likelihood of you ever having 200 amps  flowing through that is going to be so rare   plus if you calculate a service a lot  of people think that you're going to be   adding up every single breaker and it's like every  breaker adds up to like 400 amps yet it's only   a 200 amp breaker and it's because most of the  time you realize it's going to be underutilized   we're not using most of the stuff in there so  we don't have to have that big of a service   so we can kind of de-rate some things a little bit  that's one way we can think about this is a lot of   times you're not going to have 20 amps plugged  into a single receptacle you might have 20 amps   you know on the entire circuit because you  have things plugged in all over the place   so that's not actually putting any stress on one  specific receptacle that's putting stress on the   entire circuit but it's all spread out so you're  not going to have a 15 amp receptacle melting   because you don't have that one point of  contact where you're making all of the metal   inside of that plug really really hot to  the point where the plastic starts to melt   so a lot of times they know you're gonna have  these things plugged in all over the place   but in specifically where they talk about  the loads the permissible loads that are   able to be plugged into a receptacle that's  where it gets a little bit interesting   so if you look at b2 we're still in 210.21  b2 it says total cord and plug connected load   we're connected to a branch circuit supplying two  or more receptacles or outlets a receptacle shall   not supply a total cord and plug connected load in  excess of the maximum specified in table 210.21b2   so if you look at the load that's being plugged  in that's a little bit different thing than   just the receptacle itself so when you look  at that table uh you'll see that you have a   15 or 20 amp circuit rating meaning either 15  or 20 everything in this table on this row is   going to be true you can have a receptacle rating  of 15 amps meaning you have a 15 amp receptacle   but the maximum load that you're allowed  to plug into that receptacle is 12 amps   so if you're only plugging in something that is up  to 12 amps then it's not going to melt so that's   why it's okay to put a 15 or a 20 amp receptacle  on that circuit because they're saying that you're   not allowed to plug any load higher than 12 amps  in so there's just never going to be a problem   doesn't matter on a 20 amp circuit if  it is 15 or if it is a 20 amp receptacle   but that's the problem most people are not  electricians most people don't know electrical   code most people are cold in the winter and they  just want their toes to be hot so they go and plug   in a whole bunch of crap so they might plug in  two space heaters in the same receptacle and that   might draw like 21 amps well and you're thinking  okay well a 20 amp breaker is going to trip right   no not necessarily so breakers are designed to  trip at certain values so if something happens the   minimum value that is going to trip a breaker is  going to be 20 amps if it's a 20 amp breaker but   we know that breakers have two different methods  of tripping there's a thermal trip which is a slow   buildup of heat over time and for the thermal trip  to even ever engage that breaker it has to hit 130   percent of its value so that's 24 amps on a 20 amp  breaker so then if we uh that's just for heat so   21 amps being drawn on a 15 amp receptacle the  metal inside of there is only really rated for   15 amps worth of current going through it so  if you have 21 amps over a long period of time   it's going to heat that metal up so much  on the inside of the receptacle that it's   going to start melting the plastic around it and  that breaker is never going to trip it's never   going to sense that there's actually a problem  because we're not hitting that 130 percent value   and then breakers also we've talked about this in  other videos breakers have the 200 percent trip   as well and that's not a thermal trip that's  a magnetic trip and that's usually if there's   a ground fault or a short circuit there's like  a lamb like a huge impact um so it has to trip   at at least 200 percent so that's how you know  like a breaker might not actually trip even though   you've got too much stuff plugged in but it's  because we're banking on the fact that most people   most of the time are not going to be plugging  a whole crazy huge load into a receptacle most   cords are rated for a certain thing so if you  have a toaster that you plug in it might have   like a 15 amp cord because they know that toaster  is not going to draw more than you know 12 amps   or whatever so they just put a 15 amp cord on  it so when you're plugging that one device in   there's not going to be a problem but there's not  a load that comes with a 15 amp cord on it that   you buy from a store that actually draws 23 amps  that just doesn't happen they make these things   there's nema ratings manufacturers have to follow  things but the problem becomes when people plug   multiple loads in and they get over the amount  that it was designed for so if you didn't know   out there you're really only supposed to put on  a 15 amp receptacle whether it's a 15 or a 20 amp   breaker you're still only supposed to put a 12 amp  load into any one receptacle any one like duplex   receptacle so the other part that kind of mentions  this it's at least worth noting because they kind   of word it in a little bit different way is in  210.23 a it says 15 and 20 ampere branch circuits   a 15 or 20 ampere branch circuit shall be  permitted to supply lighting units or other   utilization equipment or a combination of both and  shall comply with 210.23 a1 and 2. so a1 says cord   and plug connected equipment not fastened in place  so not actually an appliance that's like stuck in   place something you just it's like portable  like vacuum cleaner toaster or something like   that the rating of any one cord and plug connected  utilization equipment not fasted in place so shall   not exceed 80 percent of the branch circuit ampere  rating a lot of people confuse this to think oh   you can't load circuits up more than 80 of the  breaker rating that's not what this is saying   it's saying any device that you plug in shouldn't  be more than 80 of that specific circuits rating   that branch circuits rating so it's the same thing  if we look at how they said in table 2 10.21 b2   on a 15 or 20 amp circuit that with a 15 amp  receptacle they're saying basically we don't want   you to plug anything more than 12 amps in  or if you look at a 20 amp circuit with a   20 amp receptacle you don't want to put anything  more than 16 amps that's a single load plugged   into this thing and 16 amps is 80 of a 20  amp circuit so it's saying the same thing   uh 80 is the same thing as whatever is in this  table down here for 16. so it's not saying that   you can't that you're like supposed to leave extra  room a lot of people think that too like you're   supposed to leave 20 so like if more things  get plugged in that's not what they're saying   it's specifically a thing that you take and  plug in shouldn't exceed a certain amount   but again we're electricians we might  know that mr and mrs homeowner mister are going to plug stuff in wherever  people are going to plug stuff in so   my rule of thumb is generally with commercial i'll  always put 20 amp devices in on 20 amp circuits i   don't ever do anything like this residential i  might do 15. the other thing reason why people   do 15 is because it saves a lot of money 28  receptacles versus 15 amp receptacles there's   they cost more there's more metal there's a  little bit more stout so they cost more plus   they're just marketed as a bigger number so they  cost more really is is probably more to do with it   than anything but with a you know home depot  places like that they sell in bulk they sell   15 amp receptacles so you're even getting  a cheaper pricing just because you get   sales they sell things in 15 amp all the time so  more put people put 15 amp receptacles in homes   especially if you're putting like 300 or like  800 if you're doing some big custom home that's   a massive difference between you know 15 amp 20  amp receptacles that's kind of why people do it   but code does allow us to do it you just got to  understand the why behind doing it but you do   need to know that people if especially if  you're in like really cold places they're   going to be plugging space heaters in so  maybe that's something you take into account   and give them dedicated circuits with a single  receptacle so they can only plug one load into it   or maybe if they wanted two space heaters in  an area give them two single receptacles on two   dedicated circuits that are 20 amp with 20 amp  space heater you know single receptacles then   you're just not going to have a problem and then  the rest of everything else you could use 15 amp   but you don't even have to do that because of code  but always remember code is the minimums it's just   minimum safety minimum you know protection for  people and equipment and things like that so   you can kind of do whatever you want as  long as you're staying within code but   it is good design good practice to to probably  just put 20 amp receptacles everywhere because   then nobody's going to have a problem you've  kind of over built the circuits and that's best   case scenario but it all comes down to the fetia  right like the the the dollar so that's why hope   you got something out of that so that is it if you  want to know a little bit more about how breakers   work i actually have a video right here it goes  over the whole 130 200 thing and actually crack   opens breakers and we talk about how a breaker  actually works and if you want to know about   specific breakers like we talk about arc fault  ground fault and dual function breakers click this   video right here so i love you crazy people thank  you so much for your attention make sure you sub   super helps me out like the video if you liked  the video and i'll see you in the next one

Channel: Electrician U

Views: 1,230,606

Keywords: electrician, electrical, electricity, dustin stelzer, electrician vlog, construction, commercial, residential, electrical vlog, electrical courses, electrician courses, electrical class, electrician class, electrician school, electrical contractor, surge protector, electrical code book, national electrical code, electrical code coach, electronic code book, terms of trade, circuit tracer, sparky life, melted receptacle, burnt biscuit, burnt receptacle, burnt plug

Id: wLSe4LzK9b4

Length: 11min 46sec (706 seconds)

Published: Mon Apr 18 2022