Amp power cable and fuse
Printed From: the12volt.com
Forum Name: Car Audio
Forum Discription: Car Stereos, Amplifiers, Crossovers, Processors, Speakers, Subwoofers, etc.
URL: https://www.the12volt.com/installbay/forum_posts.asp?tid=46112
Printed Date: April 19, 2024 at 7:39 AM
Topic: Amp power cable and fuse
Posted By: LEW15
Subject: Amp power cable and fuse
Date Posted: December 27, 2004 at 12:43 PM
i have recently bought an amp, i have all the cables but i don't know what fuse to use for the + positve cable, can anybody tell me??????? Thanks, Lew
Replies:
Posted By: jazzcustom131
Date Posted: December 27, 2004 at 2:20 PM
Look at the side of the amp. There should be fuse in the side of it. Probably right beside the Power intake on the amp. That's what you should fuse it for.
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Greed is for amateurs.
Disorder,chaos,anarchy now THAT is fun!!
Posted By: LEW15
Date Posted: December 27, 2004 at 2:54 PM
thanks, so if i was running two amps just add it and fuse it fore wat it adds up to???
Posted By: haemphyst
Date Posted: December 27, 2004 at 4:39 PM
NO, NO, NO!!! You DO NOT fuse a power lead for the load on it, you fuse a power lead for the power lead itself. That fuse is there to protect the CAR, not the amplifiers connected to it. What size power cable is it?
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It all reminds me of something that Molière once said to Guy de Maupassant at a café in Vienna: "That's nice. You should write it down."
Posted By: jazzcustom131
Date Posted: December 27, 2004 at 6:56 PM
What do you mean for the power lead itself?? You fuse an amp to control the amperageit can have. ------------- Greed is for amateurs.
Disorder,chaos,anarchy now THAT is fun!!
Posted By: haemphyst
Date Posted: December 27, 2004 at 7:42 PM
The amplifier SHOULD have it's own fuse protection. If not, you should be using a fused distribution block - that's what THOSE are for! The primary fuse in a wire is ONLY there to protect the car in case something happens to the insulation of the primary wire. If you get in an accident and a number 4 is your primary wire, and the insulation is compromised, but you do not have it fused at 150 amps, the battery can make FAR more current than that for long enough that it can cause that wire to get hot and possibly catch fire. The 150 amp fuse will prevent this from happening, also disconnecting the battery from dead-shorting against itself THROUGH THE POWER WIRE.
See this page proper fuse ratings for a given power cable. Use the chart in the lower right - the one called "Power & Ground Cable Specs". This is where you should ALWAYS fuse your power cable (or lower). That primary fuse's only job is to protect the car and primary wire, not the amplifier. Yes, if your total amplifier draw is more than, let's say 150 amps on a number 4, then you would use the next size wire, not just put a bigger fuse in, because you are already ending up with too much voltage drop to be acceptable.
Granted, IF you are running less than 150 amps through a #4, then yes you CAN use whatever size fuse makes you happy, but the fuse IS a resistance connection, and DOES contribute to voltage drop to the trunk, so why not just put the biggest safe fuse in there, and prevent as much of that drop as possible? It is OK to do that, but as I said, it's job is NOT to protect the amps... This would be simply a guideline to set the MINIMUM REQUIRED fuse value, but not the OPTIMUM DESIRED fuse value. ------------- It all reminds me of something that Molière once said to Guy de Maupassant at a café in Vienna: "That's nice. You should write it down."
Posted By: jazzcustom131
Date Posted: December 27, 2004 at 7:53 PM
Why give an amp more power than what it can use?? I would think if something needs nothng more than 20 amps, then why give it 150? I'm confused. Are you saying put a 150 fuse at the battery and two twenties at the dist block? Where's the logisc in that. That chart has ratings of maximum amperes allowed for a piece of wire. I doubt he is pushing 150 amp through that line, so there is nothing wrong with running it that way.
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Greed is for amateurs.
Disorder,chaos,anarchy now THAT is fun!!
Posted By: jazzcustom131
Date Posted: December 27, 2004 at 7:58 PM
I'm confused. Why give an amp 150 amps when it can only use 20? Fuse it at 40 at the battery, and two 20's at the dist block. That only makes logical sense. If a wire grounds out on metal, the fuse willblow man. I don't understand your logic. That guide is the maximum amperes that can be placed through that size wire. I've always been told to do it that way, and was told that by people that have been doing this for 30 some odd years.
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Greed is for amateurs.
Disorder,chaos,anarchy now THAT is fun!!
Posted By: jazzcustom131
Date Posted: December 27, 2004 at 7:59 PM
my bad on the double post, hit private messenger button by accident and thought it had erased my first one. ------------- Greed is for amateurs.
Disorder,chaos,anarchy now THAT is fun!!
Posted By: haemphyst
Date Posted: December 27, 2004 at 8:16 PM
haemphyst wrote:
Granted, IF you are running less than 150 amps through a #4, then yes you CAN use whatever size fuse makes you happy, but the fuse IS a resistance connection, and DOES contribute to voltage drop to the trunk, so why not just put the biggest safe fuse in there, and prevent as much of that drop as possible? It is OK to do that, but as I said, it's job is NOT to protect the amps... This would be simply a guideline to set the MINIMUM REQUIRED fuse value, but not the OPTIMUM DESIRED fuse value.
#1) Read my last paragraph again...
#2) An amplifier will ONLY pull as much current as it needs, no matter HOW big the primary fuse is, and the amplifier has it's OWN fuse protection.
#3) There is NO SUCH THING as allowing a component more current than is necessary (see #2). Allowing it "more than is necessary" will simply prevent VOLTAGE SAG, and therefore allow MORE EFFICIENT OPERATION. (read: less heat)
#4) OK, well then I guess the people on this board with all of their possibly HUNDREDS of years, combined, (and my 16 years experience and USNavy high voltage distribution and USNavy low voltage electronics background) don't know ANYTHING AT ALL about what we are talking about.
Ya hear that DYohn, kfr01, et al? We've been doing it wrong all this time! Please read some of the posts from the more experienced people on this board before you start questioning the information provided. ------------- It all reminds me of something that Molière once said to Guy de Maupassant at a café in Vienna: "That's nice. You should write it down."
Posted By: jazzcustom131
Date Posted: December 27, 2004 at 11:00 PM
I'm not questioning any one's knowledge, i'm just lettin you know that I do have an idea of what's goin on, dude. After your last explanation, I now see what you're saying, and you are indeed right. My bad on the misinterpretation, I was just confused with your original wording.
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Greed is for amateurs.
Disorder,chaos,anarchy now THAT is fun!!
Posted By: deocder
Date Posted: February 16, 2005 at 4:42 PM
Good thread!
I always thought that the inline fuses were there to protect the equipment. But it makes much more sense that it is to protect the actual wire.
For my situation, I am running 2 gauge from the battery with a 225 A at the battery. This goes into a fused distribution block with 3 - 4 gauge outputs. Each fuse in the distribution block will be 150 A. I've read that its unnecessary to use a fused distribution block if the amps have their own fuses. But if one of the 4 gauge legs from the distribution block gets shorted, the 150 amp fuse will blow. If the block is not fused, the 4 guage wire will see 225 A before it burns (only rated for 150 A). How would this affect the other 4 gauge legs to the other amps?
Posted By: haemphyst
Date Posted: February 18, 2005 at 11:41 AM
deocder wrote:
How would this affect the other 4 gauge legs to the other amps?
I don't understand the question... There is VERY little chance that your amplifiers will all pull enough to blow the 225A primary fuse. While for the amp's safety it is indeed unnecessary to use a fused distro, anytime you switch from one power wire size to a smaller size, you need to fuse that junction, for safety's sake. If you HAVE the #2 to (4)#4 fused block, use it... If something happens to one leg off the distro, that leg will blow, while allowing the others to remail unaffected. ------------- It all reminds me of something that Molière once said to Guy de Maupassant at a café in Vienna: "That's nice. You should write it down."
Posted By: stevdart
Date Posted: February 18, 2005 at 4:09 PM
It's all about fire safety. We should bring Sparky or Smokey the Bear back into the car audio generation with a warning "Hey kids! Only YOU can prevent car fires."
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Build the box so that it performs well in the worst case scenario and, in return, it will reward you at all times.
Posted By: sts15l7
Date Posted: February 18, 2005 at 11:09 PM
yeah...common misconception jazz the fuse on the wire is there to protect the wire from catching fire, which could ultimately lead to a fire on ur car. im sure u know this; every wire has its own max current-draw capability. a 0 gauge wire would have a greater one, obviously, than a 8 gauge. so, u should fuse the wire based on the current draw that's safest for ur wire gauge size. im doing an upgrade on my alternator wire (my alternator is 180A), and the fuse they suggested i use was 250A. it just shows that the fuse is there for the wire, not the appliances getting power from there -mir
Posted By: sts15l7
Date Posted: February 18, 2005 at 11:41 PM
deocder: i didnt understand ur question. however, i can tell u that whatever u read about not using a fused distro block if the amps have their own fuses is WRONG. ur thinking is correct: if one of the 4 gauge shorts on a non-fused distro block, there is no fuse to protect it. the 225A fuse up front will not burn, because that wire would be able to handle the current draw. however, the 4 gauge that does short might end up catching on fire, in which case itll destroy ur amp. just remember that when changing wire sizes, u must always, ALWAYS fuse... -mir
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