100 Days of the 2026 NEC Changes Day 82: 620.62 Selective Coordination (for elevators)

追加: 2026-05-31

[00:00:01][music] [music] >> Hey everybody, Ryan Jackson here. Hope you're having a great day. So, we're going to talk about selective coordination in this video. And I know it's for some people as soon as they hear those two words their their eyes just immediately glaze over and they're like, "Oh my god, please don't talk about selective coordination." Um but it it's really important selective coordination is. We don't require selective coordination for every building in the NEC, right? Certainly your house does not require any selective coordination.

[00:00:40]Uh but some some types of facilities do require the emergency systems, legally required systems back in 700 701, uh and also elevator systems require selective coordination. And this is [clears throat] a this is something that has changed a lot over the last oh dozen years or so uh because we used to have a rule for selective coordination for elevators. And the the back door was left so wide open that it never applied.

[00:01:05]You could always just get around it. Um and now they've really tightened it up to where uh selective coordination for elevators uh you really can't get away from it now. So, before I forget, when we talk about selective coordination, selective coordination uh is ensuring that the only breaker or fuse that opens during a fault is the one directly upstream of the fault. All right? So, uh if you're not familiar with selective coordination, maybe you or someone that you work with has had this experience.

[00:01:38]You're working at a job and something goes wrong and the 20 amp breaker should trip and instead the 800 amp main outside trips, right? And you know the whole building goes down because of one stupid 20 amp circuit. That is the opposite of selective coordination.

[00:01:56]Okay? Selective and coord- uh selective coordination is ensuring that that does not happen.

[00:02:02]If that happens in your house, right?

[00:02:04]You have a a fault on a 20 amp circuit and your 200 amp main trips, yeah, so what? You might have to re- reset your clocks and that sucks, right? Uh but you know, you might have to get off the couch, but nobody's going to die, right? If this is an emergency system and that happens and one fault knocks out the emergency generator and now we no longer have emergency lighting, we no longer have a system for the for the uh firefighters to uh to communicate, we lose the pressure control uh in the uh pressurized stairway.

[00:02:34]Um yeah, that's a problem, right? That could be dead bodies. So, we don't always care about selective coordination in the code. We only care about it in a few instances and article 620 is one of those instances. So, let's go ahead and take a look and uh see what we did here.

[00:02:49]So, article 620, elevators, dumbwaiters, escalators, moving walks, platform lifts, and stairway chair lifts. 620.62 selective coordination.

[00:03:00]The selective coordination requirements of this section were changed to correlate with those in articles 700, 701, and 708. So, 700 701 we know are emergency systems and legally required standby systems. Article 708 is critical operations power systems. All right, let's get going here. 620.62A general.

[00:03:23]If more than one driving machines disconnecting means Okay, so more than one elevator motor disconnect is supplied by the same source, then the overcurrent protective devices in those disconnects must be selectively coordinated with the feeders overcurrent protective device and any other overcurrent protective device upstream of it. Okay, so starting at the bottom of this uh of this drawing here, I've got three elevator motors, okay? And then above them I've got the three disconnects for them. And those are supplied by three different panel boards. But all of those three panel boards are supplied by the same switchgear.

[00:04:03]And that same switchgear is supplied by maybe a customer owned substation.

[00:04:08]All right, well, that means if I have a fault at the elevator, the only thing that should open is the fuse.

[00:04:19]Right? That is the only thing that should open. And if I have a fault on the line side between the panel board and the fuse, the only thing that should open is the circuit breaker supplying that fuse disconnect.

[00:04:34]And if I have a fault on the line side of that panel board, the only thing that should open is the switchgear.

[00:04:42]And if I have a fault between the substation and the switchgear, the only thing that should open is the switchgear is the substation, which of course is going to happen because that's the only overcurrent device upstream at that point. Uh but the key here is if this motor down here had a fault and it knocked out the switchgear up here, then we would lose all three panel boards. Never never mind the three elevator motors. We would lose probably everything in the building, right? So, we need to have selective coordination.

[00:05:14]Now, that concept and that requirement did not change. The only thing that changed is we now use the acronym OCPD for overcurrent protective device. Now, if that was the only change, I wouldn't waste your time talking about it.

[00:05:28]We also clarify that if overcurrent protective devices are replaced, selective coordination must be ensured by reevaluating the new device and all overcurrent protective devices on the line and load sides of it. Okay, so if you're in a system that has selective coordination, it is critical that when you replace a breaker, you replace it with one just like it. Okay? Don't just get any old 20 amp breaker and replace it with any old 20 amp breaker. It needs to be the exact same one that you took out, right? The same make, same model number, all of that because then it will have the same tripping cur- uh characteristics.

[00:06:06]So, if you just uh if you had a fuse and you replace it with one class of fuse, I don't know, like a class J fuse and you replace it with a class C fuse and and maybe you fuse guys out there are like, "You can't fit a J in a C." I I don't know. I don't memorize fuse classes, right? But the bottom line is if you replaced a fuse that was uh that was like a one-time fuse and a time-delay fuse, they are going to have different tripping characteristics and your coordination study is now worthless. We have no idea what device is going to open first and we'd have to redo the entire uh coordination study, which can be a rather complex thing to do. So, this section reminds us, yeah, if you're replacing overcurrent protective devices, you need to reevaluate the coordination study. Well, you don't need to do that if you're replacing this breaker with one that is identical to it because that's going to have the same tripping characteristics. But if you replace one with a different one, yeah, you got to start over. You got to make sure that it's still going to coordinate.

[00:07:07]If any additions, deletions, or modifications occur to the system, the selective coordination needs to be confirmed by reevaluating it. Okay, well, normally that would mean the utility changed their transformers, right? Um well, that would change the available fault current, right? If the if the utility changed their their their available fault current, if they changed made a bigger transformer or a a more efficient transformer, that would change the fault current, which would change all of the coordination study, so we'd have to reevaluate it.

[00:07:38]Uh changing a very large motor could also change the coordination study because remember with a motor, when I have electricity supplying a motor and the motor is spinning, it it's a motor, right? But if I shut off the source of supply, the motor's still spinning until it stops, right? Cuz it doesn't just stop. It's still going to spin and spin down. But when you shut off electricity and that motor is still spinning, it's not a motor anymore. It's a generator, right? It's creating electricity and it is feeding current into the fault. So, if I'm changing a really big motor, uh that could potentially change the coordination study. And of course, if I'm uh if I'm adding equipment, uh if I'm if I'm replacing overcurrent protective devices, so there's a lot of things that could happen that can change the coordination study and this section says you need to reevaluate it. And personally, I I think the code is probably the same with or without these words, uh but I think it's better with these words. It is it is clear that if you change the study, then you need to redo the study.

[00:08:42]We still have this exception here that says overcurrent protective devices in series do not need to be selectively coordinated if no other overcurrent protective devices are in parallel with the downstream device.

[00:08:57]You got to read that a hundred times and really slow down to capture what that just said.

[00:09:03]So, what they did in the 2026 is they added a drawing. If you're following along in the code book, you will see a little drawing in the code book. Uh it's not as awesome as my drawing, but it's pretty similar.

[00:09:14]Um because that sentence that we just read, that exception, is really hard to wrap your head around. So, we added a note that says, "Listen, take a look at figure informational note 620.62 for an example of a selectively coordinated system." All right, so looking at this, we've got our 100 amp main and it feeds uh two disconnecting means.

[00:09:37]One is a 30 amp set of fuses, the other one is an 80 amp set of fuses. And then out of the 30, we feed another fuse disconnect right next to the elevator motor and that has 30 amp fuses as well.

[00:09:50]Out of the 80 amp feeder, we go and feed two different elevator disconnects.

[00:09:55]One's 40 amps, the other one's 40-amps, right? So, we have three elevator motors from three different disconnecting means, and the one on the right, feeder two, supplies both motors M M2 and M3.

[00:10:10]So, looking at what has to coordinate.

[00:10:14]Disconnect one needs to coordinate with the main.

[00:10:19]I don't want to have a fault at the motor knocking out the main. So, disco one needs to coordinate with main, and that should be pretty easy to do, right?

[00:10:32]Especially if we're using fuses. Fuses are your best friend in a coordination study.

[00:10:37]Disconnect three, oh, I beg your pardon, disconnect two, must coordinate with feeder two and the main. So, a fault at M2 must not result in feeder two tripping or in main tripping or or opening.

[00:10:56]If I have a fault at M2, the only overcurrent device that opens should be disco two, right? The one directly upstream of it.

[00:11:04]Disco three over here needs to disconnect with feeder two and with main for the same reason.

[00:11:10]Feeder one needs to disconnect or needs to coordinate with main one so that if I have a fault down here, I'm not taking out the main, I'm only taking out feeder one. And then, of course, over here, feeder two needs to coordinate with main so that any fault down here will open feeder two, but will not open main, right? Because if I have a fault here and it opens main, then I've lost all three motors instead of just the two that should have been affected by that fault.

[00:11:48]Disco one does not have to coordinate with feeder one because these two are in series and there's no other loads in parallel, right?

[00:12:00]Disco two is in series with feeder two, but it's also in parallel with disco three. So, disco two needs to coordinate with feeder two, just like disco three needs to coordinate with feeder two, but disco one does not have to coordinate with feeder one, which makes sense because think about it. If I have a fault down here at motor one, who cares if disco one or feeder one opens? Either way, the same load is affected, which is just the motor. But, if I were to come off between feeder one and disco one and pick up some other load, whether it's an elevator or not, then disco one would have to coordinate with feeder one, right? Just like disco two and three have to coordinate with feeder two.

[00:12:50]Disco one does not have to coordinate with feeder one, but of course, everything has to coordinate with main because under no conditions should we have anything that knocks out the main.

[00:13:03]Okay, hopefully that was simple enough.

[00:13:06]Um hopefully I did a good enough job explaining it. Um I might not have, but I think that drawing that they added in the NEC is really helpful. Uh to say that, you know, you don't need to coordinate with overcurrent devices in series if there's no loads in parallel with the downstream device, I read that and I don't I have no idea what I just read. Uh I'm kind of dumb that way. I need a drawing. So, kudos to the uh to the people that uh that drew that and got it into the code. I think that was a good change and a nice clarification. So, all right, we're done with elevators. We are going to spend the next, oh, I don't know, four or five videos talking about electric vehicles.

[00:13:42]There are a lot of changes in the 2026 in article 625. We're going to cover almost all of them, so do stick around.

[00:13:52]Um you may roll your eyes and say, "Oh, who cares about electric vehicles?"

[00:13:55]Well, you may never choose to buy one, but they're not going anywhere, right?

[00:14:00]It doesn't matter if you love them or hate them, uh you need to know the rules for them because more than likely you'll be wiring one whether you whether you like it or not. So, all right, guys, we'll see you on the next video. Please be safe out there. Cheers.