what size fuse
5th Gear Member
Joined: Aug 2006
Posts: 2,447
From:
RE: what size fuse
ORIGINAL: Spyder
Ok.... That's a bit extreme PReal. Considering that to bridge a 1/4 inch gap you need a pressure of about 3500 Volts, I'd love to know what your "right conditions" within a car would be...
By the way, you don't fuse to protect the wire. You fuse to protect the circuit itself, or the power supply. The main fuse should accomodate the current draw of the entire system, protecting it from damage that may occur. If you wanted to protect the wire, then you would use a fuse that's rated at the maximum current that the wire would carry, but you don't use a 100A main fuse if you have a 250W Amp connected to AWG4 cable.
The amp's internal fuse is only the first tier of protection. Should it fail, then the next fuse up the line should protect the circuit it's attached to, not the wire itself. (And no, that doesn't mean that the fuse could be of higher capacity than the wire...). If the amp starts to fail, then a main circuit blowing in a timely manner can make repairing the amp less expensive than if it continued to bake...
Ok.... That's a bit extreme PReal. Considering that to bridge a 1/4 inch gap you need a pressure of about 3500 Volts, I'd love to know what your "right conditions" within a car would be...
By the way, you don't fuse to protect the wire. You fuse to protect the circuit itself, or the power supply. The main fuse should accomodate the current draw of the entire system, protecting it from damage that may occur. If you wanted to protect the wire, then you would use a fuse that's rated at the maximum current that the wire would carry, but you don't use a 100A main fuse if you have a 250W Amp connected to AWG4 cable.
The amp's internal fuse is only the first tier of protection. Should it fail, then the next fuse up the line should protect the circuit it's attached to, not the wire itself. (And no, that doesn't mean that the fuse could be of higher capacity than the wire...). If the amp starts to fail, then a main circuit blowing in a timely manner can make repairing the amp less expensive than if it continued to bake...
Have you ever seen a car audio fuse blow a full .25 inch, I haven't. If the fuse is a vacuum with no leaks to atmosphere that voltage would be accurate at that arc distance. There are many conditions in a car where it is possible to flash. I'm not saying it is likely, but there is a chance. It might even be worth the extra $10 for an additional fuse if your equipment is nice enough.
I have two fuses in series on both of my amps. I have a main fuse that is meant to protect me in short rated at 200 amps near the battery. I also have 2 80 fuses on my dblock to prevent an overcurrent into my amps. The 80 amp fuses fall under the 90 amp maximum recommended fuse size by diamond audio.
As ttocs said, I beleive you are mistaken on the amp's internal fuse and the power wire fuse.
The power wire fuse is there only to prevent a short circuit from causing the wire to melt and a fire to occur. In a true short, those electrons will travel fast enought to melt the insulation. I wouldn't worry about a fuse theexact max current capacity of the wire becuase the currentshould never exceed the sum of the max current of the amp and the current required to overcome the resistive losses within the circuit.The fuse inside the amp is to prevent an overcurrent in the amp.
6th Gear Member
Joined: Feb 2006
Posts: 6,936
From:
RE: what size fuse
I would never put a 200A on 4 awg, I am willing to bet that fuse has never blown? I bet that wire is stuck to the chassis before that fuse ever gets warm. I thought 4 awg maxed out around 150A? I don't like to put anything larger then 100A on it.
1st Gear Member
Joined: Jan 2008
Posts: 84
RE: what size fuse
ORIGINAL: ttocs
spyder you could not be more wrong, the fuse at the battery is to protect the wire and only the wire. Why would the fuse, almost 20 ft from the amp be for the amp? The fuse at the battery is in case the power wire shorts.
spyder you could not be more wrong, the fuse at the battery is to protect the wire and only the wire. Why would the fuse, almost 20 ft from the amp be for the amp? The fuse at the battery is in case the power wire shorts.
The way I see it is basically this: I know that my amp will draw up to X amount of amps. Even though my wire is rated to 3X amps, I would still fuse it to X amps, because any draw higher than X would mean that something is wrong with the circuit (Maybe the amp's internal fuse has arced
). since it's drawing more than expected, I would like to shut it of quick. I don't care about the wire, I care about the other component down the line that has failed. So to me, fusing at the expected draw of the circuit is the way to go, even if the wire has a higher capacity.Fuses are cheap... Cars and amps are expensive!
PReal, nothing against you doing a double fuse better safe than sorry. It's just that the conditions still seem a bit far fetched... If your electrical system is producing 3K+ volts I think you might need to worry about other things instead of the amp...
5th Gear Member
Joined: Aug 2006
Posts: 2,447
From:
RE: what size fuse
ORIGINAL: Spyder
Because the wire is part of the circuit that's being protected, but it's not the weakest link that needs protection. that would be the amp.
The way I see it is basically this: I know that my amp will draw up to X amount of amps. Even though my wire is rated to 3X amps, I would still fuse it to X amps, because any draw higher than X would mean that something is wrong with the circuit (Maybe the amp's internal fuse has arced). since it's drawing more than expected, I would like to shut it of quick. I don't care about the wire, I care about the other component down the line that has failed. So to me, fusing at the expected draw of the circuit is the way to go, even if the wire has a higher capacity.
Fuses are cheap... Cars and amps are expensive!
PReal, nothing against you doing a double fuse better safe than sorry. It's just that the conditions still seem a bit far fetched... If your electrical system is producing 3K+ volts I think you might need to worry about other things instead of the amp...
ORIGINAL: ttocs
spyder you could not be more wrong, the fuse at the battery is to protect the wire and only the wire. Why would the fuse, almost 20 ft from the amp be for the amp? The fuse at the battery is in case the power wire shorts.
spyder you could not be more wrong, the fuse at the battery is to protect the wire and only the wire. Why would the fuse, almost 20 ft from the amp be for the amp? The fuse at the battery is in case the power wire shorts.
The way I see it is basically this: I know that my amp will draw up to X amount of amps. Even though my wire is rated to 3X amps, I would still fuse it to X amps, because any draw higher than X would mean that something is wrong with the circuit (Maybe the amp's internal fuse has arced
). since it's drawing more than expected, I would like to shut it of quick. I don't care about the wire, I care about the other component down the line that has failed. So to me, fusing at the expected draw of the circuit is the way to go, even if the wire has a higher capacity.Fuses are cheap... Cars and amps are expensive!
PReal, nothing against you doing a double fuse better safe than sorry. It's just that the conditions still seem a bit far fetched... If your electrical system is producing 3K+ volts I think you might need to worry about other things instead of the amp...
Its also a huge PITA to change the under hood fuse,and the ones under the rear seats make it that much better.
I also work in anindustry where we always have a least two layers of independant protection. I guess my employeer has brain washed me to be overly safe. At least I will never blow my amp up, even ifmy car gets struck by lightening...
I think the only thing you are missing is that fuses take time to blow, and that you really do care about your wire. Rated current capacity and shortcurrentcapacity for any given wire are going to bevery different!!!!
6th Gear Member
Joined: Feb 2006
Posts: 6,936
From:
RE: what size fuse
I wanted to bring this one back up becase we are arguing the same point. If the wire has been properly chosen it MUST be fused at a point less then its max rating.
ORIGINAL: Spyder
Ok.... That's a bit extreme PReal. Considering that to bridge a 1/4 inch gap you need a pressure of about 3500 Volts, I'd love to know what your "right conditions" within a car would be...
By the way, you don't fuse to protect the wire. You fuse to protect the circuit itself, or the power supply. The main fuse should accomodate the current draw of the entire system, protecting it from damage that may occur. If you wanted to protect the wire, then you would use a fuse that's rated at the maximum current that the wire would carry, but you don't use a 100A main fuse if you have a 250W Amp connected to AWG4 cable.
The amp's internal fuse is only the first tier of protection. Should it fail, then the next fuse up the line should protect the circuit it's attached to, not the wire itself. (And no, that doesn't mean that the fuse could be of higher capacity than the wire...). If the amp starts to fail, then a main circuit blowing in a timely manner can make repairing the amp less expensive than if it continued to bake...
Ok.... That's a bit extreme PReal. Considering that to bridge a 1/4 inch gap you need a pressure of about 3500 Volts, I'd love to know what your "right conditions" within a car would be...
By the way, you don't fuse to protect the wire. You fuse to protect the circuit itself, or the power supply. The main fuse should accomodate the current draw of the entire system, protecting it from damage that may occur. If you wanted to protect the wire, then you would use a fuse that's rated at the maximum current that the wire would carry, but you don't use a 100A main fuse if you have a 250W Amp connected to AWG4 cable.
The amp's internal fuse is only the first tier of protection. Should it fail, then the next fuse up the line should protect the circuit it's attached to, not the wire itself. (And no, that doesn't mean that the fuse could be of higher capacity than the wire...). If the amp starts to fail, then a main circuit blowing in a timely manner can make repairing the amp less expensive than if it continued to bake...
6th Gear Member
Joined: Feb 2006
Posts: 6,936
From:
RE: what size fuse
http://www.powerstream.com/Wire_Size.htm
Tell me I am reading it wrong but it lists 135A as the max safe limit for 4 awg. A 200A fuse on 4 awg is almost useless isn't it?
Tell me I am reading it wrong but it lists 135A as the max safe limit for 4 awg. A 200A fuse on 4 awg is almost useless isn't it?
ORIGINAL: PReal
You couldn't have said it better though.
Its also a huge PITA to change the under hood fuse,and the ones under the rear seats make it that much better.
I also work in anindustry where we always have a least two layers of independant protection. I guess my employeer has brain washed me to be overly safe. At least I will never blow my amp up, even ifmy car gets struck by lightening...
I think the only thing you are missing is that fuses take time to blow, and that you really do care about your wire. Rated current capacity and shortcurrentcapacity for any given wire are going to bevery different!!!!
ORIGINAL: Spyder
Because the wire is part of the circuit that's being protected, but it's not the weakest link that needs protection. that would be the amp.
The way I see it is basically this: I know that my amp will draw up to X amount of amps. Even though my wire is rated to 3X amps, I would still fuse it to X amps, because any draw higher than X would mean that something is wrong with the circuit (Maybe the amp's internal fuse has arced). since it's drawing more than expected, I would like to shut it of quick. I don't care about the wire, I care about the other component down the line that has failed. So to me, fusing at the expected draw of the circuit is the way to go, even if the wire has a higher capacity.
Fuses are cheap... Cars and amps are expensive!
PReal, nothing against you doing a double fuse better safe than sorry. It's just that the conditions still seem a bit far fetched... If your electrical system is producing 3K+ volts I think you might need to worry about other things instead of the amp...
ORIGINAL: ttocs
spyder you could not be more wrong, the fuse at the battery is to protect the wire and only the wire. Why would the fuse, almost 20 ft from the amp be for the amp? The fuse at the battery is in case the power wire shorts.
spyder you could not be more wrong, the fuse at the battery is to protect the wire and only the wire. Why would the fuse, almost 20 ft from the amp be for the amp? The fuse at the battery is in case the power wire shorts.
The way I see it is basically this: I know that my amp will draw up to X amount of amps. Even though my wire is rated to 3X amps, I would still fuse it to X amps, because any draw higher than X would mean that something is wrong with the circuit (Maybe the amp's internal fuse has arced
). since it's drawing more than expected, I would like to shut it of quick. I don't care about the wire, I care about the other component down the line that has failed. So to me, fusing at the expected draw of the circuit is the way to go, even if the wire has a higher capacity.Fuses are cheap... Cars and amps are expensive!
PReal, nothing against you doing a double fuse better safe than sorry. It's just that the conditions still seem a bit far fetched... If your electrical system is producing 3K+ volts I think you might need to worry about other things instead of the amp...
Its also a huge PITA to change the under hood fuse,and the ones under the rear seats make it that much better.
I also work in anindustry where we always have a least two layers of independant protection. I guess my employeer has brain washed me to be overly safe. At least I will never blow my amp up, even ifmy car gets struck by lightening...
I think the only thing you are missing is that fuses take time to blow, and that you really do care about your wire. Rated current capacity and shortcurrentcapacity for any given wire are going to bevery different!!!!
5th Gear Member
Joined: Aug 2006
Posts: 2,447
From:
RE: what size fuse
I'm running 1/0...
Ttocs, you are 100% correct. That is the max safe current for chassis wiring. A short is a different can of worms all together. Insulation is damaged or destroyed becuase the wire is delivering enough excess current over its max safe for the resitance in the wire to create enough heat to melt the insulation..
Ttocs, you are 100% correct. That is the max safe current for chassis wiring. A short is a different can of worms all together. Insulation is damaged or destroyed becuase the wire is delivering enough excess current over its max safe for the resitance in the wire to create enough heat to melt the insulation..
1st Gear Member
Joined: Jan 2008
Posts: 84
RE: what size fuse
Well... Kinda pointless when we're all saying the same thing three different ways.
hehe... If we were talking about germs:
ttocs would be saying: wash your hands,
I would be saying: wash your hands with antibacterial soap!
PReal would be bubble boy.
http://www.imdb.com/title/tt0258470/
hehe... If we were talking about germs:
ttocs would be saying: wash your hands,
I would be saying: wash your hands with antibacterial soap!
PReal would be bubble boy.
http://www.imdb.com/title/tt0258470/
5th Gear Member
Joined: Aug 2006
Posts: 2,447
From:
RE: what size fuse
Now Now....
I wouldn't be bubble boy....
I would wash my hands and then use the alcohol hand sanitizer.
I'd much rather get sick then blow bloth my amps and burn my car to the ground though...
I wouldn't be bubble boy....
I would wash my hands and then use the alcohol hand sanitizer.
I'd much rather get sick then blow bloth my amps and burn my car to the ground though...