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hi everybody ryan jackson here hope you're doing well we're going to quickly talk about power over ethernet and the requirements in the national electrical code this will be based on the 2020 version of the nec and there actually were a couple of changes from the 2017 to the 2020 nec uh mainly some explanatory material and some clarifications but we also changed the opacity of the cables for almost every type of application so if you're familiar with the requirements in the 2017 uh nothing earth shattering happened in 2020 although there were some clarifications and again the uh the capacities of the cables were all revised as well so if we look at it historically in the nec uh we've never really dealt with power over ethernet or cables that supply both power and data until the 2017 version of the code because as some of my friends like to say you need to stay relevant and the nec never had to address it before because the technology is relatively new but this new technology is something that we need to understand and quite frankly i think electricians need to embrace i'm rather concerned and a lot of people are that commercial electricians are going to find themselves out of the lighting business before too long unless we choose to keep ourselves in that business so as the technologies evolve the code evolves to keep up but just as importantly you need to evolve and you need to stay up with it as well when i was wearing the tools i didn't want to know anything about installations over 480 i don't i didn't care about medium voltage or high voltage i didn't care about customer on substations that was just something that i didn't want to hear about because i was comfortable in my own little world i also didn't want to know anything about systems that were lower than 120 volts so i had my own little bubble 120 volts through 480 volts pretty much commercial didn't really do any residential i did some industrial stuff but i was more 120 through 480 and i think today's electricians need to come to grips with the fact that people like me are dinosaurs you either evolve or you die as they say and i think part of the evolution of being an electrician is embracing lower and lower voltages so let's talk about the requirements then we added these rules in the 2017 nec because of power over ethernet and mainly power over ethernet lighting which is becoming fairly popular so the primary concern of why we had to add this in the nec and it is low voltage and it's low current so if it's both limited in the power and the voltage and the current then why are we so concerned about it well the main issue here is reducing the threat of fire that can arise from multiple bundled cables i mentioned that we tweaked these requirements a bit in the 2020 code but again for the most part if you're already familiar with them you won't see that too much has changed so 725.144 is where we begin and that's cables for power and data class 2 or class 3 circuits that transmit both power and data must comply with a and b the conductors have to be copper and the current must not exceed the rating of the connectors all right now we're going to kind of take that line by line so that we're all quite familiar with it it starts out by saying class 2 and class 3 circuits all right well what's a class 2 or a class 3 circuit it's important to remember that class 2 and class 3 circuits are discussed in article 725 but they're defined in article 100 so for a class 2 circuit it's wiring between a class 2 power source and the equipment that it connects to and these circuits are considered safe as it relates to both electric shock and fire alright so article 725 covers remote control circuits signaling circuits and power limited circuits now here in the photograph we have a garage door opener and if you can see it's marked nec class 2. this is actually listed as a class 2 power source so the wiring between the source and the equipment that it connects to must be a class 2 circuit now this is a remote control circuit again regulated by article 725 and that means the circuit between the opener and the push button on the wall would be remote control because i'm controlling the garage door opener circuit through a relayer equivalent and it's supplied by a class 2 power source because it says class 2 and in fact when you go to 725.121 it actually says it's not really a class 2 circuit unless the power source is marked class 2 now it can also be marked as an information technology equipment power source that is also a class 2 source but for the most part you have a class 2 circuit when you have a power source that says class 2. similarly we have a class 3 circuit and that's the wiring between a class 3 power source and its supplied equipment and these circuits are considered safe as it relates to fire and safe enough as it relates to electric shock we can get some higher voltages with class free circuits therefore we don't quite have the same amount of safety as it relates to electric shock that we would have with a class 2 circuit however by limiting the voltage and the current we consider a class 3 circuit safe from fire and safe enough as it relates to electric shock now class 3 circuits are somewhat unusual a class 3 circuit a very common example would be a nurse call system but usually when it comes to limited energy circuits they're typically class 2 but you can get some class 3 as well now this is a table in the back of the codebook table 11b in chapter 9. now i'm using table b because we're going to be talking about direct current so these are the power limitations for a class two or a class three power source and you can see that the voltage can go up to 20 volts and uh for currents of 8 amps or deaths and as we go up into higher voltages then the currents start to get lower and lower and in fact down here at the bottom you can see that the power source for 0 to 20 volts the the power limitations is 5 times the maximum voltage so that would be 100 watts if i have 20 to 30 volts well then i've got some different you know that we're starting to increase the voltage which means we're increasing the shock although at 30 volts we're still not very concerned about electric shock so not much changes at that point once i get over 30 volts up to 60 volts now we've definitely added some danger of electric shock so we're really going to start caring about the power limitations and then i can go up to 150 volts on a class 2 circuit but take a look at the current it's 0.005 amps so we limit both the voltage and the current so we limit the overall power and that's why we would call it a power limited circuit class 2 is considered safe from both shock and fire and then as we look at class 3 class 3 is 60 to 100 volts and the wattage is limited based on the voltage range but either way we're going to limit it to the point where it's safe from fire and safe enough that it's not going to cause a fatal electrocution it could shock you but not kill you and to be perfectly honest probably not really even harm you but there is an increased shock danger so we do want to recognize that it does exist so that would be our class 2 and class 3 power sources so going back to the rule 725.144 class two or class three circuits that transmit both power and data must comply with a and b all right let's take a look here here we have a single port power over ethernet power source the input is 120 volts and the output is 56 volts and one half of one amp so low voltage and low current this is a class 2 power source and in fact it says down here it's a listed ite power supply this is considered a class 2 power source the conductors have to be copper and the current must not exceed the rating of the connectors these are some concepts that should not be new to us okay the conductors have to be copper fair enough we're talking about twisted pair cable uh pretty doubtful that you would make those in aluminum so the conductors have to be copper that's going to satisfy itself the current must not exceed the rating of the connectors well that's the same concept that we use when resizing conductors for electric light and power the terminals might have a lower failing point than the conductors between them forget class 2 and class 3 for a minute and let's talk about 120 volts if i've got my circuit breaker some 12 gauge wire and a receptacle my 12 gauge wire might be rated 90 degrees now can i put 90 degrees worth of current on that wire the answer is no because my circuit breaker and my receptacle might only be rated for 75 degrees or even 60 degrees c worth of heat so i could not put more than 60 degrees worth of heat on the wire not because the wire would fail but because the terminations would fail so that's something that we've been doing for a very long time in the nec if you're familiar with 110.14c and 310.15 and table 310.16 that's something that i'm sure you've done several times so the current must not exceed the rating of the connectors easy enough that's just kind of a general requirement here's an example of some power over ethernet lighting up here we have the actual power source and then we've got some twisted pair that are supplying these luminaires and that's it there is just a single twisted pair like a cat5 cable or a cat6 cable going to those lights and that's it and that's what has so many electricians concerned is that the the quote the low voltage guys whoever those might be are going to take over our jobs as electricians well i'm here to tell you that your job as an electrician probably needs to include low voltage if you want to stay relevant so this is a power over ethernet installation one of the concerns that i have with this picture and it's not addressed in the code yet is we have all of these screws penetrating the penetrating the roof and believe it or not that's not a violation yet for this type of installation i think it probably should be but 300.4 e does not apply to a class 2 or a class 3 circuit so we don't have to follow the normal inch and a half separation rule from the metal corrugated sheet roof decking so believe it or not this is not a violation not the best looking installation that i've ever seen but it is considered safe so as of right now it's compliant let's keep going there's an informational note in fact there's a half dozen of them the first one says that the cable supplying a closed circuit tv camera could be an example of a cable that transmits both power and data all right now in the example that i used here i'm showing a cable that is not a twisted pair cable so this is not a power over ethernet installation so not every closed circuit tv camera is a power over ethernet you know tv camera but some of them could be so our informational note tells us that the next information you'll notice is quite useful it says the hp 8c connector and i think that's eight pins eight contacts i know it's eight pins i think it's eight contacts uh connector which i always just called an rj45 right so the big phone connector the 8p8c connector is common for power over ethernet and most importantly the product standard limits their rating to 1 ampere at 60 degrees now that is some really useful information if i have to make sure that i'm not putting more current on these on these cables than what their connectors can handle then i better know what the connectors can handle and for a poe system an 8p8c the answer is one amp another informational note this one was added in the 2020 tells us that these requirements are based on four pair balanced twisted pair cables all right so utp is unshielded twisted pair four pairs right so we've got four p four pr four pairs unshielded twisted pair type cmr communications riser rated 75 degrees c i think we're all familiar with uh with what 75 degrees c is and then over on the left to the left of the circle it says 23 gauge and reading the uh the cable jacket and deciphering what these letters and numbers mean is actually something that we're going to have to do to comply with the requirements of 725.144 so understanding what those different numbers are is is actually fairly important the next informational note tells us to take a peek at a particular ansi nema standard for information about power over ethernet lighting alright so this is a poe power source and you can see that the output is 21 volts with 23 watts per port and that is for our power over ethernet lighting so you know with leds how many uh how many lamps can you get off of one of these drivers you know it depends on you know the size of the lamps and the size of the driver of course here's where the rules really kind of kick in when they first added this in 2017 i was a little bit confused because with class 2 and class 3 they're considered safe from fire and safe enough from electric shock and i was kind of thinking well why are we adding all of these requirements about cables if you can't kill somebody and you can't light a fire with it and the answer to that is well you can't light a fire with one power limited circuit i'll i'll stand by that i mean that's what the definition says and i agree but what happens if i put one amp on a whole bunch of individual wires and then group a massive bundle of cables together well the heat in the center of that bundle of cables is going to be pretty significant enough that it could potentially melt the insulation of the surrounding cables and conductors and then end up having a fire and lighting the building on fire so the concern is cable bundling and it says the ampacity of class 2 or class 3 balanced twisted pair cables is determined using table 725.144 for ambient temperatures up to 86 degrees f alright so as we look at the table there's a table here for one through seven cables in a bundle eight through 19 cables in a bundle 20 to 37 cables in a bundle and if you have your code book open you'll see that it goes even farther than that then we've got our temperature rating 60 75 or 90 degrees c let's go ahead and do an example really quick if i've got a bundle of 15 cables and they're all this cable here in the photograph that is a what 75 degrees c four pair 23 gauge all right so i go down the size here on the left 23 gauge 75 degree column i said we had 15 of them in a bundle that means i could put what 1.11 amps on each individual piece of copper in that cable however the connectors are only going to be rated one amp is that correct so we would have to make sure that we're not putting more than one amp through this cable not because the cable is going to melt but because the connectors could and as we go across you can see that the number of cables in the bundle as that goes up the opacity goes down it's really no different than the way we handle mc cable or the number of wires in a piece of emt look if you have a bunch of wires or cables or conductors that are bundled together then we have to decrease the ampacity there's also a table note that says for bundles of more than 192 cables or for conductors that are smaller than 26 gauge the ampacity has to be calculated using engineering supervision 192 cables is a pretty big bundle but let's be honest some of us have been in some older buildings where we've been remodeling you know indefinitely for the last 50 years and you get some pretty crazy cable bundles you know a bundle of more than 192 cables isn't beyond the realm of possibility so if we have that and they're carrying both power and data then we would need to get some engineering supervision to help us figure out the opacity the other table note tells us that if only half the conductors in the cable are carrying current so maybe two for for uh current and then two for the data then the opacity can be increased by a hundred and forty percent now that's the opacity of the cable that does not change the rating of the connector if the connector is only rated one amp that's usually going to be the limiting factor so i would tell you not to get too carried away about that because i think in most installations it's the connector that's the weakest link it also says that for temperatures greater than 86 degrees f the correction factors in 310.15b apply so just like th hhn and xhhw and everything else the opacity is based on a maximum of 86 degrees f if it's higher then the opacity decreases using the correction factors in 310.15b so same concept that we have for conductors and light and power we're applying to power over ethernet there is an exception and this was added in the 2020 and it needed to be it says look for loads of 0.3 amps or less cables with 24 gauge or larger conduct conductors do not need to comply with any of this like if your load is 0.3 amps then forget it we're not going to be killing anybody with that small amount of current we're not going to be lighting fire so we can just ignore it all together the last thing is 725.144 b which talks about a dash lp cable now i know that there is a a dash lp cable out there that's listed as of today which is january of 2021 as of today i'm not sure that you can even buy it yet but there is a listed version of it out there for class 2 or class 3 cables that have the suffix dash lp for those cables those are designed to be installed in a bundle and you can just go right off the marked opacity of the cable regardless of how many con cables are in a bundle so it's designed to be bundled together just go right off the rating or if the rating is lower than what the table would allow then you can go off the table but what i want to point out here is the suffix dash lp not just lp but dash lp and i know that's frustrating but if you can look at this rather blurry picture here this cable has three different markings cmp cl3p fplp so that means it's a communications cable that's plenum rated it's also listed as a class 3 plenum rated cable and it also listed fplp for fire power limited so power limited fire alarm cable and it's plenum rated so the fact that it ends with the letters lp does not make it a dash lp cable it would have to say like fplp dash lp so again they do make that cable i've never seen it but from my understanding it should be on the market pretty quickly all right with that said we're going to wrap it up i hope you guys are staying safe out there in the covet 19 era hopefully we're getting towards the end of that but if you're interested uh head over to my website for books follow me on instagram ryan jackson electrical facebook ryan jackson electrical dot train uh ryan jackson electrical training and youtube ryan jackson electrical make sure you like subscribe and do all those wonderful things but most importantly have a great day