Amp Sizes on Distribution Block?

[blowhole]

Budding audio noob here:

I will be running 1/0 awg power wire from my battery to a distribution block, then from the dist. block with 4 awg power wire to the two amps -- one 4 channel and one mono amp. I will be putting in an inline fuse 12" off the battery, and the dist. block is a 2 anl fuse block. The mono amp takes 40 amps, the 4 channel amp takes 60 amps.

Questions: What size anl fuses do I need in the dist. block? And what size fuse will I need in the inline fuse holder at the battery?

Opinions: Will a 60 amp anl fuse work for the 40 amp mono amp? Will a 80 amp anl fuse work for the 4 channel amp? And will a 200 amp fuse work for the main power fuse?

I look forward to everyones expert opinions and suggestions!

Thanks in advance!

[tm311]

Originally Posted by blowhole

Budding audio noob here:

I will be running 1/0 awg power wire from my battery to a distribution block, then from the dist. block with 4 awg power wire to the two amps -- one 4 channel and one mono amp. I will be putting in an inline fuse 12" off the battery, and the dist. block is a 2 anl fuse block. The mono amp takes 40 amps, the 4 channel amp takes 60 amps.

Questions: What size anl fuses do I need in the dist. block? And what size fuse will I need in the inline fuse holder at the battery?

Opinions: Will a 60 amp anl fuse work for the 40 amp mono amp? Will a 80 amp anl fuse work for the 4 channel amp? And will a 200 amp fuse work for the main power fuse?

I look forward to everyones expert opinions and suggestions!

Thanks in advance!

the amps themselves have fuses in them...so you do not need to use a fuse at the distribution block...just at the battery. This of course can be argued....that it might be possible to melt the smaller 4ga wires in the short span between the DB and the amps and start a fire before any of the other fuses pop....but that is a bunch of crap..it can't happen. But if you arleady have the fused DB, then you could get buy with matchign the fuses already in the amps...or smaller because there is NO way your going to be able to give either one of those amps the 40 and 60amps you quoted.

[blowhole]

Originally Posted by tm311

the amps themselves have fuses in them...so you do not need to use a fuse at the distribution block...just at the battery. This of course can be argued....that it might be possible to melt the smaller 4ga wires in the short span between the DB and the amps and start a fire before any of the other fuses pop....but that is a bunch of crap..it can't happen. But if you arleady have the fused DB, then you could get buy with matchign the fuses already in the amps...or smaller because there is NO way your going to be able to give either one of those amps the 40 and 60amps you quoted.

Thanks for the reply.

So if I stick with the amp sizes I quoted in the 'opinions' line, I should be fine?
Also, is the 200 amp anl fuse at the battery an appropriate size, considering the amperage of the amps themselves?

[tm311]

sounds good.

[cupidstoy]

max fuse size is determined by the wire used "downstream" from each fuse. depending on the gauge wire you use and the length of the run, that will determine the amps of the fuses. the only thing the amplifiers themselves have to do with them is you need to make sure you run big enough wire to power the max draw on the amplfiers at peak output and fuse according to the wire used.

this is because you run the risk of the wire turning into a big fuse if a short occurs. if the fuse is a slow blow and too big for the wire, the wire will start to melt and catastrophic failure can occur usually ending in a fire.

it think it is good advice to NEVER run an unfused wire in your vehicle (except for the very short run from the battery to the first big fuse) and to ALWAYS make sure the wire downstream of the fuse can handle more amps then the fuse itself.

also note, the amp power your quoted is probably RMS or average power and max current draw at peak output could be twice the average. just something to consider. don't skimp on wires and fuses. your ears, amps, peace of mind and insurance company will thank you. now is the time to do it right since you are running all new anyway.

i think this is the chart you're looking for:

http://www.powerstream.com/Wire_Size.htm

if you're running the wire outside of a loom and the amp is close by, 4 guage is good for 135 amps. in a loom or if the amp is in the trunk and battery in the engine compartment, it's only good for 60 amps. either way, if you only use the 200 amp anl fuse and don't fuse each block, you run the risk of burning the 4 guage wire. i would fuse each wire separately and run a slow blow that is at or just under each wires capability to carry current.

[tm311]

Originally Posted by cupidstoy

max fuse size is determined by the wire used "downstream" from each fuse. depending on the gauge wire you use and the length of the run, that will determine the amps of the fuses. the only thing the amplifiers themselves have to do with them is you need to make sure you run big enough wire to power the max draw on the amplfiers at peak output and fuse according to the wire used.

this is because you run the risk of the wire turning into a big fuse if a short occurs. if the fuse is a slow blow and too big for the wire, the wire will start to melt and catastrophic failure can occur usually ending in a fire.

it think it is good advice to NEVER run an unfused wire in your vehicle (except for the very short run from the battery to the first big fuse) and to ALWAYS make sure the wire downstream of the fuse can handle more amps then the fuse itself.

also note, the amp power your quoted is probably RMS or average power and max current draw at peak output could be twice the average. just something to consider. don't skimp on wires and fuses. your ears, amps, peace of mind and insurance company will thank you. now is the time to do it right since you are running all new anyway.

i think this is the chart you're looking for:

http://www.powerstream.com/Wire_Size.htm

if you're running the wire outside of a loom and the amp is close by, 4 guage is good for 135 amps. in a loom or if the amp is in the trunk and battery in the engine compartment, it's only good for 60 amps. either way, if you only use the 200 amp anl fuse and don't fuse each block, you run the risk of burning the 4 guage wire. i would fuse each wire separately and run a slow blow that is at or just under each wires capability to carry current.

So you can show me evidence of 4 ga wire burning in any situation? As long as it was properly fused AT the battery? I would LOVE to see that. I said in my initial post that some people would say fused DB blocks are required...but I also said it was completely not true....and I stand by my original comments. I also question why running the wire in a loom would change the fuse reqirements....thats the first I heard of that...is that science....or some kind if iasca rule?

[cupidstoy]

sorry, didn't mean to ruffle any feathers here ;-) but i always do enjoy a good discussion and maybe i might learn something so here it goes....

my understanding is the wire's current carrying capacity is dependent on temperature. i think we can agree the cooler a conductor is, the more current it can carry. see superconductor experiments always occuring as near absolute zero as possible.

so, put it in a loom, less ability for heat to dissipate (no convection, very little conduction through plastic loom) as it builds up due to the natural resistance of the conductor. same for longer runs. we know that running a 100 foot extension cord takes a higher gauge wire then a 50 foot one for the same amp carrying capacity. same principle. also, a good part of the wire is in the engine compartment which gets pretty hot in some spots. essentially, as it gets hotter and hotter, the wire carries less and less current. what is that? a resistor. converts current into heat. possibly resulting in fire or melted carpet, etc in the cabin or where ever the wire runs. so, you have to fuse the wire based on its application and location. i think you could do a quick google search and confirm that wire runs inside a loom or long wire runs result in less current carrying capacity.

here's another graph of wiring specs for different loads.

Car audio cable recommendations
This info in from rec.audio.car FAQ (orognally 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

you can see that wire gauge changes as the distance of the run increases and that even 2 gauge isn't recommended for over 150 amps if going over 10 feet from the power source.

you're probably right about it being very rare for a 4 gauge wire to melt down, but i do believe the theory on this is right. fusing a 4 gauge wire with 200 amp fuse would not be "up to code" in my book. although you could probably get away with it in most cases.

just my personal opinion. but, i'm a self admitted conservative when it comes to stuff like this, so take it with a grain of salt. just wanted to provide a different view point on the topic ;-)

short answer is use a 100-120 amp fuse at the battery to serve the DB and fuse each wire going to the amps with the 40 and 60 respectively. you're not fusing the amps (they already have them) you are fusing the conductors for a worst case short to ground scenario.

[blowhole]

My initial objective was to fuse the 1/0 awg main power wire with a 200 amp fuse at the battery. Then at the DB, fuse the two 4 gauge wires with either 60/80 amp fuses. Each step-down of wire size would also have a coordinating step-down in amperage allowed. Since the amperage of the 4-channel amp is 60, then I was going to limit the 4 gauge power wire to that amp to 80 amps. The amperage of the mono amp to the subs is 40 amps, so I was going to limit the amperage for the 4 gauge power wire to 60 amps.

So, 200 amps limited through the main power wire to the DB. Then a combined total of 140 amps allowed through the DB to the amps ( 80 and 60 amps respectively). Will this step-down from battery to DB, then DB to the amps provide both sufficient protection and raw power that the amps will need??? Is my logic on supplying power and protection accurate?

Thanks for the replies thus far -- I believe my current plan will properly protect the amps and provide enough power needed to efficiently utilize the amps.

[blowhole]

P.S. Or should the step-down of amperage at the DB be equal to the fuse size of the amplifiers themselves? If the amps fuses are 60 total -- should the DB fuse to that amp be 60 also?? Or higher??

Thanks again!

[cupidstoy]

i was just readin' up on that very thing. you can go 20 amps higher then the amplifier fuses on each leg of the DB. it's actually recommended due to slight losses in the transmission (heat and voltage drop).

here's a good read that exactly addresses your questions: http://www.termpro.com/articles/powersys.html

also, i would suggest making sure you have good connection terminals on the main power wire. soldering the crimp on connectors seems like a good idea.

good luck and have fun!

[czechm8]

Its always a good idea to fuse the individual wire runs to each amp. Could you get away without doing it. probably, but its cheap insurance.
Run wires to the amps that can handle the max draw and fuse each line at the DB with a fuse slightly higher than the max draw of the amp. Your main run should be able to handle the max draw of all amps and fused appropriately.

Remember that current flows both ways. If you should accidentally ground out one of your amps power wires, the most damage you could do is blow the fuse at the DB. If your DB is not fused, you could overload the line to your other amp and damage it in this situation. I've done this before......I accidentally grounded the run to my front stage amp and blew the fuse at the distro. It only cost me a fuse and not my sub amp too.

Here is a link to some very good and complete information you will find usefull:
http://www.bcae1.com/

I'm running two amps and I will explain how I have mine wired as an example:
My main run is 0 gauge with a 200 amp fuse to a distro block that splits to two 4 gauge runs. One 4 gauge run powers an amp with a max of about 50 amps and is fused at 60 amps. The other run powers an amp with a max draw of 90 amps. It is fused at 100 amps. The combined draw of both amps is well within the capabilities of the 0 gauge main run and allows me room to upgrade in the future. The 4 gauge wire can handle up to about 130 amps and the 0 gauge can handle 325 amps.
You will find very little 2 gauge options. Lots of 4 gauge and lots of 0 gauge. Its never a bad idea to run heavier wire than you think you will need because most of us find a need for more power and have to re-wire anyway. I did, which is now why I'm running 0 gauge.

[blowhole]

Awesome -- that is very good information and opinions from people with experience. I appreciate it. My initial ideas and assumptions were correct and you guys have validated that. Thank you!

czechm8: Your install will nearly mimic mine -- I appreciate the example. That takes the worry out of that part of my install. And I agree, I do want room to grow in the future in terms of power availability. I will keep you posted.

cupidstoy: Thanks for your input. That is common sense. I appreciate the links, that is good information.

Thanks guys!

[tm311]

Originally Posted by czechm8

I
Remember that current flows both ways. If you should accidentally ground out one of your amps power wires, the most damage you could do is blow the fuse at the DB. If your DB is not fused, you could overload the line to your other amp and damage it in this situation. I've done this before......I accidentally grounded the run to my front stage amp and blew the fuse at the distro. It only cost me a fuse and not my sub amp too.

But wouldn't the amplifier fuse protect the amp in this case? Back in the olden days I always ran a fused distribution block, but now that all the amps are coming fused I just don't see the need. BUT i agree that it won't hurt anything either. Of course it goes without saying that you should NEVER be working on your amps power wire without first removing the main fuse at the battery, right?

[czechm8]

Originally Posted by tm311

But wouldn't the amplifier fuse protect the amp in this case? Back in the olden days I always ran a fused distribution block, but now that all the amps are coming fused I just don't see the need. BUT i agree that it won't hurt anything either. Of course it goes without saying that you should NEVER be working on your amps power wire without first removing the main fuse at the battery, right?

Yes, you should remove power before you work with it, but we're all human and make mistakes too.
Yes, the fuses in the amp should protect it, but they will not protect the wire to it, which is where a potential problem could exist. Cheap insurance and piece of mind.