166. Idea - Circuit Breakers vs Fuses

00:00 Chris: 

On this episode of EECO Asks Why we're going to be talking about the difference between circuit breakers and fuses, and I've thought, you know what? Let's bring in our resident expert, Jonathan Fuller, and he's going to walk us through it. And you guys may remember Jonathan, he's been on many episodes, including how to read a one-line, the most popular EECO Asks Why episode we've ever had. So sit back, get ready. This is going to be a fun one. 

And if you haven't sent us your industry war stories, please send us a DM on Instagram or Facebook, because we want to feature those in an upcoming episode of EECO Asks Why, if you have questions about how to do that, just reach out on our social media platforms and we'd love to chat.

Now, let's hear from my friend, Jonathan Fuller, as he breaks down the difference between circuit breakers and fuses. Cue the music.

Welcome to EECO Asks Why. Today, we're going to be talking about circuit breakers and fuses. How do you pick between them, what's providing me the best protection for my equipment? There's just a lot of different options to go out there. And today we'll be talking with Jonathan Fuller, our product manager of South Carolina. So Jonathan, welcome. 

01:12 Jonathan: 

Hey, thanks for having me. 

01:13 Chris: 

I hope you're doing good today, buddy. 

01:15 Jonathan: 

Oh, it's just another day in a isolation paradise. How about you?

01:19 Chris: 

Yeah, that's right. This is the new normal, so moving forward, man. So I really appreciate you taking the time with us today, though. Pretty interesting topic, circuit breakers, and fuses. Every plant out there has them we've all been into plants and seeing the storerooms that are full of spare breakers, and then you go to the fuse bin and man, they can be fun to play with. Right. And see all the different types of fuses that are out there. So maybe we'll just start for our listeners with just with a basic definition of what a circuit breaker is and what a fuse is.

01:50 Jonathan: 

Yeah, absolutely. A fuse is going to typically be, if you kind of think of like a light bulb in your house it's going to be some kind of insulating material with a filament in the middle of it. Typically a piece of metal or something like that that when the fuse starts to overheat, due to over current, that metal is going to melt or break, and that's going to break your circuit, just like a light bulb in your house when it burns out that filament is broken. 

And then a circuit breaker is going to be.... it's more of a mechanical kind of device and it's going to have a magnetic solenoid inside and sometimes also a bio metallic strip that when it starts to heat up that strip's going to bend. And that's, what's going to actuate your circuit breaker. 

02:31 Chris: 

Okay, very good. So what are the main differences between circuit breakers and fuses? 

02:36 Jonathan: So some of the main differences are going to be a cost. So fuses are typically going to be less expensive than a circuit breaker, but that's due to the fact that fuses are kind of a one and done kind of deal, once that fuse blows you're going to need to replace it. Whereas the circuit breaker, when it trips, you're going to be able to just reset it. So circuit breakers are typically more expensive as well as again, how they react. So a fuse is going to react very quickly to an over current whereas a circuit breaker is going to take a little bit longer to reach that over.... not necessarily reach that over current state, but it's going to take longer to react to that over current state in a circuit breaker. 

03:14 Chris: 

Right. Right. So maybe let's talk through advantages of each cause they are, each one does have advantages. Right, 

03:22 Jonathan: 

So again, you know, fuses are less expensive. They're going to quickly react to that overload. So it's going to be typically for a more sensitive electronic. You're going to want to have that fuse on it. But one of the disadvantages of a fuse is that if you've got a circuit, that's usually going to have some inrush current or over current or surges on it, that's going to cause those fuses to blow.

Another disadvantage of a fuse is you typically, unless you've got a great vendor managed inventory through us here at EECO, you're not necessarily always going to have that extra fuse laying around. So sometimes people, customers will go in and they'll select the wrong fuse to replace that with. So, whereas they might need a 20 amps, slow blow fuse. They might end up putting in, a 25 or 30 by accident, not realizing that they grabbed the wrong one or they might be out of it. 

Whereas with the circuit breaker, some of the advantages are it's going to, again, when it trips, you're going to be able to just kind of verify the reason that it trip makes sure that reason doesn't exist anymore. And then you're going to be able to reset that circuit breaker and go on your way. But they're going to be a little bit more expensive than just fuses. But then again, the disadvantage of that they're expensive to replace and then they don't react as quickly to a power surge as a fuse did. So sometimes if you have more sensitive electronics or devices connected to it that could actually cause damage to those devices because the circuit breaker didn't react quickly enough. 

04:48 Chris: 

Gotcha. Okay. Very good. So let's get to the heart of a couple of things here, trying to make the decision between a fuse and a circuit breaker, vice versa. Are there any general rules of thumb that you would offer up to our listeners for helping make this the right decision for their application?

05:04 Jonathan: 

It all depends on that application. So, if you've got some sensitive electronics or things like that, you typically are going to want to use a fuse to protect that. If you've got, just, everyday things. You can just use a circuit breaker on those. That'll kind of, if they're not very sensitive to those inrush currents but then also it also, again, depends on those inrush currents and things like that and your circuit.

So if you're prone to a lot of that, inrush current and things like that depending on your downstream circuit as to whether or not you want a fuse or a circuit breaker. It also is going to kind of depend on your application, as far as whether you need combination arc fault breakers for like residential or whether you're going to need ground fault because then, you're going to typically want to go with a circuit breaker instead of a fuse. 

05:50 Chris: 

Right, right. Very good. Well, let's maybe let's talk a little bit more about the different types because within circuit breakers and within the fuse families, there are all different types and that could be separate episodes of itself, right? But maybe a high-level overview of some of the different types of devices within fuses and circuit breakers for our listeners to think through. 

06:14 Jonathan: 

Yeah, sure. So, I mean, there's going to be a lot of different kinds of fuses. And all those fuses they're going to have some of the different characteristics inside of them, whether they're something that's called like a slow blow fuse, or whether it's something that's going to allow it to quickly blow the fuse. And then there's going to be different kinds of filaments and things like that inside those fuses and whether it's a cartridge fuse or power regular fuses. And then, again with circuit breaker as well you can have ground fault circuit breakers. You can have multipole circuit breakers for two phase three phase power.

You can have arc fault circuit breakers as well as in circuit breakers and you can start getting into electronic trip units and things like that would be able to adjust the different ratings of that circuit breaker to be able to, have different trip ratings. So it, it might triple in 10 amps or I might trip on 15 amps or the different, short-term and instantaneous and long time tripping characteristics of that. So with the circuit breaker, you can really kind of dial into what you need in that circuit and adjust different characteristics to coordinate a system together. Whereas with fuses, you can't necessarily do that. 

07:25 Chris: 

And with fuses, I think to one, the one takeaway that hopefully our listeners are getting is, not all 30 amp and fuses are created equally, right? They are different, and you potentially could damage your equipment if you don't have the right fuses, I mean, I'm thinking like drive fuses, protecting a variable frequency drive, they're special, highspeed type fuses that are in place to protect that special electronic equipment.

07:52 Jonathan: 

And I mean, just like with circuit breakers, fuses, you have some fuses that only work on AC some fuses that only work on DC. And so that's going to be a common characteristics between breakers and fuses. So it's all about selecting the right fuse for your application or the right breaker for your application, 

08:11 Chris: 

Absolutely. I'm thinking back to a previous episode we did on EECO Asks Why so far is when a breaker tips it typically trips for a reason. So, that doesn't mean let's just go crank it up a little bit more, right. Or it also doesn't mean if it's a 30 amp fused that blew, maybe we just need to go to 35. Typically these devices are engineered with the right proper schemes to protect that equipment, so let's talk about trip curves on breakers because that's going to help determine the right type of breaker that we want, right? So how do we select that proper trip curve?

08:45 Jonathan:

So on your trip curve for your breaker, you're going to have a, it's going to be a graph of your two axes, your X and Y axes. So typically on your one axis, you're going to have time. And on the other axis, you're going to have multiples of current. And so a lot of it depends on what application you're doing, what you're trying to protect.

This graph is going to show you okay for this time period and this multiple of current, I'm not going to trip. And then once you exceed that curve then it's going to trip. So, you might have something that at a half a second, you can go 200% of your rating and it won't trip. And then after that, it will trip instantaneously.

So, you know, your curves are just going to be different applications for different projects. And if you've got like a motor or something, that's going to have a high amount of inrush current, you want to make sure that you're selecting the right curve for that, because otherwise if you don't select the right breaker and that you have all that inrush current that your motor and circuits designed to handle that breaker could trip out. And that could cause some issues in what's commonly referred to as nuisance tripping. And just because you didn't select the right kind of curve. 

09:52 Chris: 

Absolutely. And that ties back to what we talked about in previous episodes, making sure you have the right coordination too, cause you don't want to trip a breaker upstream versus the breaker that's closest to the device, right. Or closest to the fault. 

10:07 Jonathan: 

Right. Cause then you could end up taking down half your facility just because you didn't have the proper coordination instead of, tripping that breaker right there at the source of the fault, for that motor circuit or whatever it might be, you could take something, upstream, that's providing power to five or six different kinds of circuits or panelboards.

10:24 Chris: 

So let's talk fuses now, how do you select a proper rating of the fuse that I need for the application that's an it question? 

10:33 Jonathan: 

So, I mean, you know, like you mentioned earlier, I mean, there's so many different kinds of fuses, a class L, class, RK5, CC fuses, class J I mean, there's all these different kinds of fuses for different applications. Like you mentioned some drive fuses specifically for variable frequency drives or fuses specifically for things like a motor and things like that. So depending on what kind of application you're using is going to be what kind of fuse you want to use. And some of them are fuses that will blow a lot quicker than others. I mean, some are called slow blows, so it'll take them a little bit longer to break or things like that. Again, just like with circuit breakers, you want to make sure you're using the proper class fuse for your application and make sure it's a fuse designed for that application.

Because if you have something that doesn't have the right characteristics for your circuit, just like a circuit breaker, it could cause something upstream to blow instead of the one that you typically want. And then that could potentially have a safety issue. 

11:33 Chris: 

Absolutely. One best practice we haven't really talked about here, but you know, if you're going to replace a fuse, go back to the drawings and verify, that the fuses that you're pulling out was correct, first of all. And then that the fuse that you're putting back is for that same rating because I mean, oftentimes, we've all been there, things need to get up and running.

11:52 Jonathan: 

Let me stick a penny on here and let me get up and running. 

11:56 Chris: 

Well, hopefully we're not doing pennies. Hey, I have seen them though. Those linked type fuses. I don't know if you've seen those before you know, there's a lot of things you could do with those fuses, so that's what I say it's probably a good practice and something to think about for our listeners to just go back to those drawings, verify what was, originally engineered and designed, and then go back with that because then in a pinch, decisions could be made that maybe potentially damaging to that equipment.

12:25 Jonathan: 

Yeah, absolutely. And I, I've seen some customers that'll kind of just do whatever they can to get by, but then I've also seen some customers that they actually label, on their machines, they'll label, use a five amp, RK five fuse only in the circuit. So they actually with the label maker, they just put a label right there where that fuse goes in that circuit and say, make sure you're using only this type so there's no confusion of, Hey, what kind of fuse do I need? What amperages it just because, like you said, just because this is the fuse that was in that circuit there's no telling if the person before you put something in there that was wrong in a instance before you, so, it's always great to go back and reference that drawing or have it labeled clearly right there so that everybody can kind of see, like, this is undeniably, what's supposed to be here.

13:08 Chris: 

That label that you were just referring to, where was that at? 

13:12 Jonathan: 

It was actually, so in the control cabinet where the fuse was mounted inside of that cabinet, they just took, with the label maker and made a little label that said a class RK five, five amp fuse only and just stuck it right there on, on that panel. So that way when they're looking in there that blown fuse and pulling it out, there's no question of, what's supposed to be there.

13:33 Chris: Wow. That's a really great best practice that I hadn't really seen that to that degree, but you know that thank you for sharing that, Jonathan. 

13:42 Jonathan: 

Yeah, absolutely. 

13:43 Chris: 

For EECO Asks Why we like to get to the why to help out heroes understand why this stuff's important, how they can help them, from a safety standpoint, from a development and growth standpoint. So why is it important to understand some of the fundamentals when we're trying to figure out the right protection scheme for our equipment? 

14:01 Jonathan: 

At the end of the day, safety is the number one priority of everybody. It should be. You want to make sure that you're selecting the right kind of fuse or the right circuit breaker to make sure that in the event of something like an overcorrection or things like that that, that device, that fuse or that circuit breaker is the right one and it's acting the way that it's designed to act so that it will shut that circuit down so that it doesn't cause any issues downstream or upstream or wherever.

So that person is safe so that there's no kind of incidents where it can prevent a fire from wire melting or it could prevent an explosion or things like that. We always want to make sure that we're selecting the right break on the right fuse because that's the right brake on the right fuse for a reason. And that reason is safety. 

14:46 Chris: 

Absolutely. Absolutely. Well Jonathan, thank you so much. You brought a lot of insight, a lot of knowledge to this topic. I think this is going to help our listeners, from a safety standpoint and also from an application standpoint and reliability. If you're using the equipment that's designed for the system, reliability should increase.

And if breakers trip or fuses blow, there's probably a indicator. And there's a reason for that. And that's what we need to get to the root of from a root cause analysis standpoint so that we can get back up and running properly. So thank you so much, Jonathan, for your time and your expertise. And I do hope you have a great day.

15:24 Jonathan: 

Thanks for having me. You too.