Now we're going to talk about maximum overcurrent protection. It's a funny wording, but that's what's labeled on most units. They call it maximum overcurrent protection. So another word for overcurrent is, well current we know is amperage or speed of electron flow. So we have maximum amperage protection.
Or, we can think of it as maximum overcurrent being we want something that's going over that current. So, maximum fuse protection. So if we replace the word overcurrent with fuse or breaker, that translates to maximum breaker size, maximum fuse size.
So maximum overcurrent protection, maximum fuse size, maximum breaker size. So look on this unit, it says the maximum fuse or amp. or maximum overcurrent protection, 30 amps. So that means the largest size is 30 amps.
30 amps, no larger. So if I read on the fuse itself, says 30 amps, I'm good. Anything under 30 amps, I'm still going to be good.
But if it says 31 amps or 35 amps, that's going to be bad. So I need to make sure on this unit that the amperage on there is... For sure, no larger than that size rated on it. Maybe it says 35. Whatever number it says, you've got to make sure that the breaker at the main panel, also the fuse and disconnect before this unit, is no larger than that. That's the maximum, the absolute largest it can be.
That's one of the things that we want to make sure that we keep lined out. Now, there's another number on there that's also just as important. So this other number goes to the other end. We have a maximum for a fuse.
Now we're going to have a minimum being the smallest size wire. So if we read on here, we're going to see another set. And this one's going to say, also it says on here, minimum circuit amps.
So it says over here, minimum, and then it says circuit amps. Minimum circuit amps. And what this one says is minimum circuit amps, 17.6.
And this is minimum, the absolute smallest number that can mean. And what we're going to use this for, minimum circuit amps, is the smallest for sizing this wire. So what we're going to do is pull up our app. And what we're going to do is pull up a wire sizing app. This is one of the apps that electricians use.
So I got a folder called HVAC, and this is where I keep all of these apps. So on this one, I actually use the app called Wire Size Calculator. If I pull this up, it says line amps. And this is where I'm going to put that number. I'm going to put in here 17.6.
That's going to tell me what size amperage that I have to have at minimum on this unit. So the next thing is, this is what changes. This is why they can't tell you what size wire goes to this unit, because it depends on the length.
The length of the wire is going to determine what size wire that's going to be. So if I measure this, and I measure 8 feet up, and I measure 20 feet across, and another 10 feet across, I'm looking at 38 feet. So in here where it says length, I'm going to put over here 38 feet.
I'm going to hit next and it tells me 12 gauge wire. 12 and then AWG which stands for American Wire Gauge. That means that the wire coming to that unit has to be a minimum of 12 gauge, American Wire Gauge.
Now, in wire gauging, the size of the wire gets thicker as the number gets smaller and it also gets thinner as the number goes up. So when it says a minimum circuit amps of 17.6. For the distance of this example, I would need 12 gauge wire or thicker. I could use 11 or 10 or 9 or any other size that we can get, but it has to be minimum of 12 gauge wire.
My fuse can be no longer than 30 and my wire has to be a minimum of 12. Now, maybe my distance was a whole lot longer. Let's say that maybe our wire length was going to be 110 foot. So I'm going to put it at 110 for 110 foot.
So if I do it with 110 foot at the same minimum amps, it says now I have to have a number 8 wire, or larger. So that's why it says minimum circuit amps is used to size the wire. Now we're not going to be sizing and actually running wire to our units. That's the electrician's job.
However, it's very, very, very, very important for us to be able to look at this unit and know. I'm not talking about the wire that comes from the disconnect to the unit, which is also important, but also the wire coming to the disconnect. We want to look on that wire and look somewhere on that wire for a 12 or whatever number and see what size it is. When we do our calculations, we need to make sure that the wire inside of that box coming to it is the correct size. If the wire coming to our unit is too small, that's going to cause a fire.
and you don't want to have a fire. So what we want to do is be sure that we identify that. Now it's on the back side of that disconnect, we have to have an electrician do that.
But we want to make sure we set that call up with the customer, we'll get that customer in there to get their electrician or maybe our own electrician, if your company offers that, so that we can have the correct size wire. If we fuse the size wrong and that wire is size two, or fuse the size right and the wire is too thin, then we could have a fire issue. So we cannot let that happen.
We got to make sure that we're operating safely. So it's very important for us to be able to identify that that's the correct size wire. It would be great if they could put, hey, you need a number 12 wire coming to this unit. But as we can see in this example, the first example we needed 12 gauge wire at minimum, and the next set we needed 8 gauge wire at minimum. So we want to make sure we use the correct size wire to this unit so we don't burn anybody's house down.
Even though we don't run that wire, we have to identify that problem. Many times people put in a larger air conditioner. which is a whole other category of issues.
But if you put in a system that's larger and it needs larger amperage, and they put in the larger breaker for it but never change that wire size, the wires could overheat, melt, burn the house down. So these are two very important numbers we need, and they're on every single air conditioner. It's going to be on every tag of every unit.
Maximum overcurrent protection, in other words, the largest possible fuse or circuit breaker size, and minimum circuit opacity, the smallest sized wire. The other thing you need to look for, is what type of fuse it might be. In this case, this one says a time delay fuse or an HVAC breaker. This is an inductive load. It's going to have a high inrush of currents, which means there's going to be a surge over the amperage of that breaker.
It could pull over 30 amps for a very short amount of time, and a slow blow fuse or a time delay fuse or an HVAC breaker will allow for that inductive load. The other problem is on electric heat, we want to use fast blow fuses. Electric heat doesn't have a big inrush.
If we start over-amping, they want to shut that down right away. So you want to read on the unit, and it'll tell you what type of fuse to put on there. It's very important.
If you read the instructions, follow these instructions, it works great. The app for sizing the wire is fantastic. We don't run that wire.
We want to make sure that that wire is the correct size, though.