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Breakers vs Fuses


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theskydive814 
Member - Posts: 7
Member spacespace
Joined: September 14, 2002
Location: United States
Posted: September 18, 2002 at 9:50 AM / IP Logged  

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
chasesaccessori 
Copper - Posts: 198
Copper spacespace
Joined: August 22, 2002
Location: United States
Posted: September 18, 2002 at 10:09 AM / IP Logged  

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
theskydive814 
Member - Posts: 7
Member spacespace
Joined: September 14, 2002
Location: United States
Posted: September 18, 2002 at 11:10 AM / IP Logged  
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
Velocity Motors 
Moderator - Posts: 12,488
Moderator spaceThis member has made a donation to the12volt.com. Click here for more info.spaceThis member has been recognized as an authority in Electrical Theory. Click here for more info.spaceThis member has been recognized as an authority in Fabrication. Click here for more info.spaceThis member has been recognized as an authority in Mobile Audio and Video. Click here for more info.spaceThis member has been recognized as an authority in Mobile Security and Convenience. Click here for more info.spacespace
Joined: March 08, 2002
Location: Manitoba, Canada
Posted: September 18, 2002 at 6:33 PM / IP Logged  
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 !! Breakers vs Fuses -- posted image.
Jeff
Velocity Custom Home Theater
Mobile Audio/Video Specialist
Morden, Manitoba CANADA
dj baracus 
Member - Posts: 22
Member spacespace
Joined: July 28, 2002
Location: United States
Posted: September 23, 2002 at 8:16 PM / IP Logged  

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?)

toolapcfan 
Member - Posts: 15
Member spacespace
Joined: October 20, 2002
Location: United States
Posted: October 20, 2002 at 3:18 PM / IP Logged  
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.
garcia1980 
Member - Posts: 14
Member spacespace
Joined: August 21, 2002
Location: United States
Posted: October 21, 2002 at 2:22 PM / IP Logged  
yo, I'am on the same boat!
jG
go2pac 
Copper - Posts: 179
Copper spacespace
Joined: May 04, 2002
Location: California, United States
Posted: October 21, 2002 at 3:06 PM / IP Logged  
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
NyxBass 
Silver - Posts: 226
Silver spacespace
Joined: March 14, 2002
Location: United States
Posted: October 21, 2002 at 5:15 PM / IP Logged  
I really suggest you check out    http://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
toolapcfan 
Member - Posts: 15
Member spacespace
Joined: October 20, 2002
Location: United States
Posted: October 22, 2002 at 8:05 AM / IP Logged  
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?
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