Breakers vs Fuses
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=3756
Printed Date: April 28, 2024 at 5:02 PM
Topic: Breakers vs Fuses
Posted By: theskydive814
Subject: Breakers vs Fuses
Date Posted: September 18, 2002 at 9:50 AM
Hey guys..... I'm deciding how to wire my new system in the monte, and I'd like some opinions on breakers vs. fuses. I have two amps (kenwood 2x200 & PPI 4x40). The Kenwood has two 20 amp maxi fuses in it already. The PPI manual says to use a 50amp or less fuse. I was thinking of having inline fuses between the power distribution block and the amp, and putting a breaker at the battery. they way each amp could pop it's own fuse if something went wrong, but if the 4AWG power wire shorts, it'll pop the breaker. I've never used a breaker before and just wanted some advice. berk ------------- Seeing Double and Feeling Single....SS style baby
Replies:
Posted By: chasesaccessori
Date Posted: September 18, 2002 at 10:09 AM
The set up you are thinking of works extremely well, I have used it with every show car I have constructed. If you have other acessories in the car you might want to consider making a breaker box by the battery and just run a 0/2gage wire from the battery to the breakers and then a smaller gage wire to your amps, etc. If you could set things up the way it is most needed for an audio competition you would have it like this: Battery-circuit breaker-fuse(by the distribution block)-distribution block-fuse(by the amps,etc)-(your amps, crossover, etc). ------------- (owner/installer)
Chase's Accessories
Ridgecrest, CA
in business since 92
Posted By: theskydive814
Date Posted: September 18, 2002 at 11:10 AM
thanks for the info....I figured that would work well. I'm not into comp cars, it's just a hobby for me. The only thing left for me to decide on is whether or not to use a capacitor. I think I'll set it up w/o and evaluate performance.
-------------
Seeing Double and Feeling Single....SS style baby
Posted By: Velocity Motors
Date Posted: September 18, 2002 at 6:33 PM
If you have the capacitor... use it. It will help relieve stress on your electrical system and also add punch to your subs and speakers when voltage does not drop. Do it man !!!.... Just do it !!  ------------- Jeff
Velocity Custom Home Theater
Mobile Audio/Video Specialist
Morden, Manitoba CANADA
Posted By: dj baracus
Date Posted: September 23, 2002 at 8:16 PM
thanks to all who replied to this topic, it has really helped me, as well i am upgrading my setup, & have a question(s) re: fuse sizes...
currently i have a total of 60A, so i have an inline fuse holder with an AGU style fuse. The holder maxes out @ 60A, (so does the fuse style, i believe). when i am finished, i will have a total of 90A in the system. What kind of fuse style (or breaker) is recommended for a 90A+ load?
(i have a fusable dist. block with 3 outputs (60A +15A +15A). I am considering adding a CAP also. In chasesaccessori's "diagram", where can i add it? can i put it AFTER the dist. block, before my sub-amp, or should i go BEFORE the dist. block? (i would help out if it was AFTER, because i could mount it in the trunk, with the amp and sub. (does the CAP need a seperate ground?)
Posted By: toolapcfan
Date Posted: October 20, 2002 at 3:18 PM
This is the idea I plan to do as well since I'm adding a few non OEM features like power windows and locks as well as an alarm and a two amp stereo system. My question refers directly to fuse sizing though. I have a Fluke 86 Clamp meter that I bought so that I can read actual DC current loads. Awhile back I sold some power windows to a guy and I was doing all the preliminary work for him, like determining wire and fuse sizes and drawing up diagrams. ( why? because I'm too nice for my own good, spent the better part of 8 hours doing all of that). Anyways, so I was checking the locked motor amperage draw of these power window motors, and I had an inline fuse installed to protect the test wiring and the switch I was using. Well the motor drew well over 20 amps when locked. I don't know about DC fuses/circuit breakers, but I know that AC breakers/fuses can handle 125% of what they're rated at, and you're only supposed to load a circuit to 80% of it's rated load. Well considering a 5 amp fuse didn't blow when I had the power window motor locked I'm thinking the same nubmers must not apply to DC automotive fuses. I know that temperature and wire length affects loads and that fuses can have different speeds as far as when they'll blow, but this was a cheap 5 amp ATO fuse. So I don't get how I'm supposed to determine fuse sizes. I always go overkill on my wire sizes so that's not really an issue, but I want my fuse/breaker sizes to be as close to the actual running amperage as possible without nuisance trips/blows. But the 20+ amps pulled through the 5 amp fuse has me feeling like I'm back at square one and don't know jack about what I'm doing. Can anyone shed some light on this for me? Can't find jack on the internet. TIA for any help.
Posted By: garcia1980
Date Posted: October 21, 2002 at 2:22 PM
yo, I'am on the same boat!
-------------
jG
Posted By: go2pac
Date Posted: October 21, 2002 at 3:06 PM
Even though a fuse is rated at 5 amps does not mean it will blow when 5 amps is exceeded. I almost want to say that it can handle about 3x the amount of current, BUT, only at a certain amount of time.
-------------
Karl
Pacific Accessory Corporation
Mobile Audio Interfacing Equipment
Connecting You to Your Music Since 1976
Posted By: NyxBass
Date Posted: October 21, 2002 at 5:15 PM
I really suggest you check out https://www.eatel.net/~amptech/elecdisc/caraudio.htm read the "fuses" section. The fusing is not to protect your components. They have their own fuses for that. The fusing is to protect your power wire. The fuse size shoudl be determined by the WIRE size and length, NOT by your components. If you have a bigger draw than you can provide on that wire safely (consult the chart on above site) Then you need to upgrade your power wire, not the fuse. Good luck! ------------- /NyxBass
Posted By: toolapcfan
Date Posted: October 22, 2002 at 8:05 AM
Thanks for the link, that's a great website! I see your point, although load must be determined in order to determine wire gauge, followed by fuse/breaker size. Additionally, the website does not address wire length. Someone who didn't know better would look at the chart and say, oh, my amplifier has a 20 amp fuse, so I should be able to use a 12 gauge wire to run it. But we all know this is not the case, he should use a minimum of an 8 gauge wire. Then he asks why? And I don't have a straight answer for that, other than, you just do. Although the NEC book is tough to navigate, the answers are rather clear and there to be had (except for determining panel size). But that book doesn't deal with automotive DC. So what's the definitive source of info on this stuff? I like to be able to use ohm's law in combination with given quantities to determine these things. Not to have to rely on various websites, which may or may not have the correct information. I don't like to leave it to chance like that. These people didn't pull this information out of nowhere, they had to get it from somewhere. So where'd they get it?
Posted By: NyxBass
Date Posted: October 22, 2002 at 5:40 PM
It is a function of ohm's law in combination with established values for copper wire gauge vs resistance. This info in from rec.audio.car FAQ (https://www.mobileaudio.com/rac-faq/) (originally from IASCA handbook). To determine the correct wire size for your application, you should first determine the maximum current flow through the cable (looking at the amplifier's fuse is a relatively simple and conservative way to do this). Then determine the length of the cable that your will use, and consult the following chart: Length of run (in feet) Current 0-4 4-7 7-10 10-13 13-16 16-19 19-22 22-28 0-20A 14 12 12 10 10 8 8 8 20-35A 12 10 8 8 6 6 6 4 35-50A 10 8 8 6 6 4 4 4 50-65A 8 8 6 4 4 4 4 2 65-85A 6 6 4 4 2 2 2 0 85-105A 6 6 4 2 2 2 2 0 105-125A 4 4 4 2 2 0 0 0 125-150A 2 2 2 2 0 0 0 00 This is what I often use to consult. It is the accepted competitors chart, and what the safety inspectors at sound off often use. If you would like some background stuff for the math, go here: https://documents.epanorama.net/documents/wiring/wire_resistance.html first. The numbers they have in here are equivilent to the ones given in my electronics text for my college analouge electronics course. From these numbers, you can apply Ohm's law and variants to create your own Table of exact values, if you are so inclined. The values in the chart above are somewhat rounded to be safe. If you need help working it out, post back here and we'll walk through it. ------------- /NyxBass
|