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“Installing the wiring for an aftermarket car audio system you ve probably heard of using using these things right here fuses. But why do we need these do we need if amplifiers have their own built in fuse. What size fuse do we need what is the right way to set up everything with fuses for multiple amplifiers. How long should our wire be from the battery before we add a fuse what type of fuses should we avoid that s all coming up in this video all about car audio visas welcome to car audio fabrication my name is marc and here on this channel.
I do gear overview videos. I do build log videos and i do lesson videos like this video all about helping you learn how to master car audio. So if you enjoy that kind of thing i would love to have you as a subscriber. So first things first why do we even need a fuse we all know that when we re installing a new aftermarket amplifier we need to run a power lead from the battery to that new aftermarket amplifier.
A fuse is meant to protect a circuit. In this case. The circuit being from the battery to the amplifier and back a very common misunderstanding that i hear is people will say well my amplifier already has fuses on it to protect it so i don t need a fuse on the wire. And this couldn t be more wrong well you have to understand is a fuse is protecting the full circuit.
So not only the gear that is part of that circuit. But it s also protecting the wire that is part of that circuit you see if we don t have a fuse and the power wire connected to the positive lead of our battery touches. The ground. Which is the body of the vehicle.
We create what is called a short circuit a huge rush of electrical current occurs so much so that the wire can t actually handle that amount of current and the wire will start to get hot hot to the point that it can easily start on fire. So lesson. Number. One here is that the fuse also protects the wiring.
But fuses come in many different shapes and sizes can we take just any fuse and put it on a wire and now that wire is protected from a short circuit. Not necessarily because the fuse rating might be too high for the size of the wire that we re using we re going to talk more about this than picking the right size fuse in a little bit. So how does a fuse work inside. There ll be a small stripper metal.
Where all this metal kind of next down. And it gives us a failure point. So if there is too much current going through the fuse exceeding the fuse rating. It will burn through that small amount of metal thus breaking and opening the circuit.
So there are many different styles of fuses. Which style fuses should you be looking to use for par audio for high current applications. Where you re adding an amplifier. I recommend a nl and mini am l.
Style fuses. You can get these in many different current ratings. Easily up to 300 amps for smaller devices with a smaller required current you re going to use these kind of fuses here. These are blade style atc and atm.
Which are the smaller versions of this style fuse. The few style that in my opinion. You should avoid are these glass style fuses. The way that these are held in a fuse block.
It has a small little spring type clamp that goes on each end and a lot of times. That spring clamp can just become kind of weaker over time which can lead to not that great of a connection. Which leads to resistance in the connection and heat and a lot of times you ll just see people having issues with these i would recommend to stay away from them..
So what actually holds the fuse and connects it to our wiring. There are different styles of fuse holder and we ll start with this one right here. This is what i would call an inline fuse holder. Most all fuse holders will have a protective cover that we can remove and in this case.
I call this an inline fuse holder. Because you ll have one input and one output usually this is going to be our main system fuse and this is going to be closest to the positive terminal of the battery. And i want to go into a little side note real quick here how close to the battery should this be i see it all the time where in the instructions of the company will recommend that this is within 18 inches of the positive terminal of the battery. But what i want to point out is it s not really so important the actual length as taking into account how that wire actually connects from the positive terminal of the battery to the fuse block.
What s actually important here is you want that length to be as short as possible because you have to understand that that length upstream of this fuse is not actually protected so what could happen is if that wire comes disconnected from our fuse block here and it touches ground there s no fuse between the positive battery terminal and the end of that wire. So that wire could cause a short circuit and start on fire that s why instead of using the 18 inch length recommendation. I like the recommendation of keeping that length as short as possible and if you would like you could also zip tie the wire to different areas in the vehicle. So if it did somehow become loose from here.
It doesn t have the possibility of actually touching ground. Now you will find inline fuse holders. In different sizes based on the style of fuse that it uses. This is an al style fuse.
So it s a much larger fuse block. But they also have inline fuse holders for mini al which are considerably. Smaller and i want to point out. Here that just because a fuse is smaller doesn t necessarily mean less performance or anything.
Like that you re more going to find that larger fuse blocks like this that can attach to larger wire are usually going to use the larger wire size. But there are fuse blocks that have a large hole for like a zero gauge wire. Where you can still use the mini al style fuses. If you re only doing a simple system with one added amplifier you re not adding.
Processors and a bunch of other equipment. An inline fuse holder is the way to go and really. This is the only fuse that you re going to need for that simple one connection system. Now what if we re doing a complex system with multiple amplifiers multiple pieces of gear.
My kind of system then in that case. We re gonna need an inline fuse solder up by the battery. But then back by the gear. We re gonna have what s called a distribution block in this case.
You definitely want what s called a fused distribution block. Now there are distribution blocks that don t have fuses built into them. And i just want to point out that you have to be careful with those type of distribution blocks. Because when you go from a large wire to a smaller wire remember that that smaller wire has a smaller current handling capability.
So if this is not a fused distribution block you can only use a fuse on your inline fuse holder upstream that is sized for that smaller wire. I ll talk more about this when i show you our system example with the distribution block. The point is that you re going to have a feed wire coming and you re gonna have multiple wires. Coming out for your different devices.
And with each of those multiple different wires. You can do a different sized fuse you can even get more fancy and have a distribution block that feeds a wire to another distribution block for several smaller sized devices. The biggest thing i want you to take away is anytime you reduce the size of your wire..
The fuse rating. Should not exceed the max current handling capability of that wire. So let s talk about that how do you choose what size fuse perhaps. I could give you some clues yeah.
That was a bad attempt at a rhyme. But i will show you guys exactly how we can determine what size fuse. We need in just a second here first i want to thank our monthly channel sponsor new concepts when it comes to car audio wiring and connection accessories. My go to source is new concepts their power wire comes in a wide variety of different sizes and colors to match any application for rca signal wires.
They have all sorts of different options based on your budget. How many channels you need and the length of the wire. They also have a full line up of different battery terminals fuse blocks and distribution blocks definitely consider them for your next system and you can check them out at new concepts. Dot com.
Or at the link down in the video. Description. So. Let s talk about choosing the fuse size so to explain what size fuse you need i ve drawn an example system you ll see that we have the battery up top with its positive lead.
Which is connected with a wire into the inline fuse. The inline fuse has another wire. Which comes down and goes into a distribution block and then that distribution block has several wires coming out they go to two different amplifiers and we ll just say a digital signal processor. Now remember these fuses are meant to protect not only our gear.
But also the wiring so we have to take both into account to determine what size fuse that we need now we re going to find that with many amplifier companies if we look in the instruction manual. We re going to see the recommended fuse and wire size. But what if we have multiple amplifiers or what if they don t tell you what to use in the manual. I rather teach you guys how to do this so here s the equation that we re going to use current or i equals power and watts over we re going to start with determining how much current all of our devices.
Need at their max output. So first let s talk about the amplifier power for our system. In this case. I have in a thousand watt amplifier and a four hundred watts.
If we add that together that s fourteen hundred watts of power now we have to remember that no amplifier is a hundred percent efficient so let s say that this is a class d amplifier and it s 80. Efficient so we re gonna do fourteen hundred divided by 08 and if you were using. A class. A.
B amplifier you would use. 05 to 06. Somewhere in that range. It s not super.
Important. Let s just say there were eighty percent efficient so this top number is actually going to be seventeen hundred and fifty watts. I talked about this in a previous video and some people were confused so again an amplifier cannot be a hundred percent efficient. You can t take a hundred percent of the power coming in and convert it to a hundred percent output.
It s only going to be in this case with a class d. Amplifier 80. Percent efficient which means..
We actually need seventeen hundred and fifty watts of power coming in to actually get that fourteen hundred out now for our voltage at the bottom number. We re going to use our system running voltage let s just say thirteen point eight volts this could range from thirteen point a up to fourteen point four in this case. Using thirteen point eight. So if we do 1750 divided by thirteen point eight.
We get a hundred and twenty seven amps so we know that this part of the system is 127 amps. I know with my dsp manual. It told me four amps so we know this is about a hundred and thirty one amps of total current that we re going to need to pull through this guy here. Now here s the thing.
Though they don t make in a hundred and thirty one amp fuse. They make one hundred and twenty and they make in one hundred and fifty so usually if you re close you re just gonna step up to the next size fuse in fact in my case. I would actually probably step down to the a hundred and twenty just to be extra safe and because again remember that we re only going to be pulling that amount of current when you are at a hundred percent full tilt volume like literally playing a sine wave. That s the other thing that i think a lot of people get confused would they think just because they re at max volume.
They re pulling max current through their system. When you re listening to music. You re not if you re listening to a sine wave. And it s literally just one constant bar blast of energy.
Then yes you are actually pulling this much current but in my case. I know that i m gonna be okay with a hundred and twenty amps now remember when we did this easy math calculation. It was for the total of our system. Power.
What about each of these separate individual little fuses for that is simple you just do each individual leg. So if i was doing a thousand. Watts i d do a thousand divided by 08. Which is my efficiency number and then i m going to do that over 138.
Volts that gives me ninety point five so in this case. I m going to use in a hundred amp. Fuse for that amplifier now is there a good way to check your math yes. There is if you take the amplifier and you look on the side of it if it does have an actual fuse built in in this case on this amplifier.
It s a 300 watt amplifier. And it has a 30. Amp. Fuse so let s do the calculation really.
Quick 300 divided by 08. Percent efficiency divided by thirteen point eight volts this gives me about twenty seven amps. So they should be using a 30 amp. Fuse.
Which they are as another quick side note. This is a great way to figure out if the amplifier companies are lying to you if you find this value. And then the fuse value on the amplifiers is considerably smaller hate to break it to you. But that amplifier is probably not making the rated power.
Now the next aspect of this is sizing our wire correctly. So we would do those same calculations again. I came up with about 131 amps through this leg..
So in order to size this wire. I can use a chart like this i ll put it up on screen for you guys if i had 131 amps it falls in right about here and if i knew i needed that little leg from here all the way back to the back of the vehicle to be about 16 feet. So between 15 and 18 feet. I know that i would need a zero gage.
Run going there. Now what about these smaller runs. Here. Let s say.
I know. This is gonna be about five feet long for my distribution block to my amplifier. We know that it s about ninety point five amps that means this wire would need to be about four gage using a chart like that is important for determining your wire size. Because where people will get into trouble is they ll do something like using an unfused a distribution block.
Where there s no fuses here. It s straight connected and they ll step down from zero gauge down to four gauge and they think that that s okay. But they forget that this fuse here can actually handle more current going through it than that four gauge wire can and that s where you end up. Having issues is if this four gauge wire shorts out it is going to burn.
Before this because it becomes the fuse it can handle less current than what the actual fuse cabinet. So that wire can burn. So the takeaway here is whenever you re stepping down from a larger wire size to a smaller wire size. You definitely should be using a fuse to protect that smaller wire size.
So we know how to pick our fuse size. But what about some fuse myths. The most popular myth that i hear by far is that adding a fuse puts a bottleneck on your system in one way you know what i guess you re right it does put a bottleneck on the system. Because we ve introduced an intentional failure point.
If we do have a short circuit. We want it to fail inside this views. We don t want it to light the wire on fire and catch our vehicle on fire. But the problem here is i think some people look at the fuse and think that it somehow is limiting their system.
The idea here is if you ve done your calculations you re picking a few size that is slightly larger than the max amount of current that you could ever possibly pull through this fuse. So. The point is you re never going to get to the point that that fuse is limiting your system. Because if you sized.
Everything correctly it would blow by then in my opinion. Where this myth comes from is people use fuses and fuse holders. That really aren t of the best quality and they do actually have a lot of resistance across that fuse. Which does limit the performance of the system if you want to learn about measuring resistance and measuring voltage drop.
I have a great video for you that you would enjoy that you can check out right up here you can also check out some of my other videos here on screen a special thanks to new concepts for being a monthly channel sponsor and a thank you to anthony bernard. Brian william marcos. Michael jeremy doug. Steve emmanuel.
Jerry and the rest of the patreon membership team big thanks to all those guys for making the ” ..
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