power wire size?

happy thanksgiving to all!! I was just wanting to ask a question about wire size for a 500 watt amp. would 4 gauge or bigger be to much for the amp and would it cause it to get more current than it should? thanks for any help guys! David

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BASSSS!

Excess battery and wire size does not push current into load, only voltage can do that.
The bigger the better.

ok. thanks a lot! how about fuse size? this amp doesn't have any external fuses and draws about 100 amps. what size inline fuse would be good for it?

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BASSSS!

The amp should have its own fuse(s).

The fuse for the wire (4G etc) as close as practical to the supply (battery) end is to protect the wire in case of a short. It must be rated no greater than the wire rating (else it's the wire that can fuse and cause fire) but can be smaller provided it handles the load.

For a 500W amp I'd expect a max of ~50A, hence say a 60A fuse or larger. (General rule is to size wires & fuses at least 20-30% above load rating - ie, wires ^& fuses should not (generally) be run at more than ~70% of their rating,)

Post edit: I just reread your OP. If the amp draws 100A, then IMO a 130A fuse tho 120A should be ok (especially considering it probably rarely runs at full power). But maybe 150A is a more common fuse, hence 150A with wiring of at least 150A. (I think 4G covers that, but check with others. There are current versus wiring size charts & info on the12volt & elsewhere.)

yeah, it's the 2nd edition of the orion 225 hcca digital reference amp and doesn't have external fuses. thanks for the info though!!

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BASSSS!

If it needs you to supply its protection fuses (unbelievably [IMO] some do that) fuses the manufacturer should advise the size & type (unbelievably [IMO] some don't do that), but they are placed close to the amp and are different to the wire protection fusing - or rather, usually are, especially if that wire supplies other loads.
However some move the "electronic" (amp) protection fuse(s) to the supply end to reduce voltage drops or to only need the one size & type of fuse as spare.

so if I put an inline fuse next to the battery, that would help voltage drops?

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BASSSS!

You already have a fuse near the battery. (Or you should. If you don't, I'm leaving this thread.)

lol...yes I do. but I also have a distribution block near the amp.

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BASSSS!

Does the amp have its own fuse (even if internal)?

And is the wiring from the DB also 4G - &/or are powering other things from it?

not sure about internal fuses. and yes, the wire from the dist. block is also 4 gauge. I have this amp on 1 fuse and a electronic crossover and a small amp for my components on another separate fuse.

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BASSSS!

So another amp also from the DB thru a fuse?

You can have the amp protection fuse at the battery keeping in mind that it now covers BOTH amps (ie will operate on the sum of the amps plus the small amp's current).
And again, the amp's manual should say what size (& type) of fuse(s) it has, else specify what type you need to provide.


But DO NOT confuse a load's (amp's) protection fusing with that of the distribution. Many loads may have fast-blow fuses (slow blows aren't a problem - it just means the distribution fuse may blow instead).

And re fuse voltage drops, the real dedicated use non-resistive circuit breakers (magnetic sensing) as they are effectively an in line relay as opposed to a resistive protection device.
Of course, good high-power amps should not vary output power as a result of reasonable voltage dips - ie of up to a few volts.

ok. so I looked up the manual for my amp and it calls for a 35 amp fuse. so if I have a fuse at the battery and one at the dist. block,i would need like a 20 amp fuse at the battery and a 20 at the dist. block instead of putting like a 30 or 40 amp fuse in each end..right?

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BASSSS!

No - fuses in series are not "additive". EG - 30A passes thu both so both would be overloaded.   
Normally the 35A amp protection fuse would be in the amp, but for recalcitrant fuseless designs you'd place it near the amp power terminals.
Your distribution fuse - eg, 100A or whatever - then protects the distribution (until the next downstream fuse).

If you have to provide your own fuse, or if you want a single fuse, then you'd use a 35A fuse for distribution (even if using 100A cable etc). But then you would probably go direct to the amp rather than the added hassle and cost of a DB.
Any low power loads could then be taken off the amp power input.


What amperage or power is the other amplifier?

the other is only a 50 watt x 2 that I have wired in stereo.

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BASSSS!

So that's an extra 20% on the 500W amp.

So you could use your DB with (say) 100A (of 4G) to each and a fuse up to 100A (or rated for the 4G) at the supply/battery end with fuses - if needed - for either/both amps at their power terminals...
Most would use a big fuse for the cable to the DB and then smaller fuses (and wires) more suited to each load at the DB ouputs.

Or if the 500W requires you to supply its 35A fuse, a 35A fuse at the battery end (that assumes the 2x50W = 100W amp has its own fuse). But the if the 100W draws 10A, the 500W amp can only draw up to 25A.

BTW - fuses will typically handle 10% over-current for at least several hours - ie, a 35A might handle 40A for hours or 45A for many minutes. However, as before, running above say 70-80$ of fuse rating decreases the life of the fuse. And several overloads of say 110% or 120% will cause accelerated failure even if it survives each individual overload (ie, thermal fatigue).   

ok. sounds like I may need to start out with like a 50 amp fuse at the battery and a 35 at the dist. block for starters. the small amp has the factory original inline fuse holder for it.

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BASSSS!

if your main power run from battery to distribution block is 4 gauge then i would use a 60A fuse as my main to allow full current to pass through to each amp being powered from that main power wire, then at the distribution block i would use the recommended fuse for each amp.

the main fuse is there to protect the wire against burning up from being shorted and your fuses in the DB will protect the amps.