fuse size

i donthave a specific question here, but how should you figure what size fuses to use on power wires?

Power & Ground Cable Specs
Cable Size Wire Gauge	Current Capacity Amperage (amps)
1/0	350
2	225
4	150
8	100
10	60
12	40
14	25
16	15

go through and look in the general information. lot of usefull stuff.

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ac delco am radio and sparkomatic 40 watt sound exploder

The numbers in the chart are the absolute largest fuse recomended for each specific size of wire.  Whenever possible to use a lower fuse it is a very good idea to do so.  This is especially important with wires larger then 4awg.

The best way to size fuses is to do so based off of manufacturer recomendations.  Simply add up all the maximum loads and that is the size fuse you should use.  If the manufacturer doesn't recomend a fuse size you can get a general idea based on the fuses in the amp (if it has any). 

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Kevin Pierson

so say if an amp has a 300 amp fuse, is that the size fuse i should use at the battery?

knotdrummer88 wrote:

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so say if an amp has a 300 amp fuse, is that the size fuse i should use at the battery?

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No.  The fuse on the amp is designed to protect the amp.  The fuse you use at the battery is determined by the size of power cables you install.  The purpose of the battery side fuse is to protect the wire.  So if you have an amp that can demand 300 amps, you'll need to use 0AWG cable (and upgrade the big 3 to 0AWG and install a high output alternator system) and protect the cable with up to a 350A fuse or circuit breaker.

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Support the12volt.com

knotdrummer88 wrote:

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so say if an amp has a 300 amp fuse, is that the size fuse i should use at the battery?

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If it has a 300A fuse and it is the only device on the power wire then a 300A fuse at the battery would be sufficient.  Make sure your wire is physically large enough to support 300A and you'll be fine.

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Kevin Pierson

The problem then is two same rated fuses without discrimination.   

You may find blow one, replace both. Not that both will blow, but the survivor may be compromised (severely heat treated etc).


What KP says is true in principle, but in practice the amp's fuse would be removed & bridged - unless it is a special fast-blow or slow-blo etc. But even then, that fuse would normally be transferred to the battery end.

Otherwise be prepared to replace both fuses (eg one, then soon afterwords, the other. )

ok, so if one fuse blows always replace both. and would one fuse ont he amp and one on the wire be fine? and what about more than one fuse on one wire?

Yes.

As long as the fuses are not rated for more current than the wire can support, then you can have a wire made entirely of fuses...

That's overkill and completely unnecessary, of course, but you can have multiple fuses in a single wire. You will ALWAYS fuse whenever you go from one wire gauge to another, as well.

haemphyst wrote:

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...you can have a wire made entirely of fuses...

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..but not if you want a low resistance cable.
(And only one fuse needs to be rated less than or equal to the cable!)

I finally convince someone on another forum NOT to fuse the ground path(s!) as well.
Though the normal "hot" logic won out (along with open-ground damage), reliability, repair cost and the avoidance of fuse/breaker resistance were also benefits.

Just in case anyone takes Haemo literally, or thinks there is any advantage or benefit from multiple fuses....

ok thanks guys, this helps