What fuse size?

[DOOM_NX 10+ year member]

Hi, I recently added a second amplifier to my setup (Kicker ZX300.1) and my installer put a power distribution block before them. He didn't seem too confident to me about the fuse types he used. He placed a 40A fuse in the kicker line and a 50A fuse in the Hertz line... Is it ok?

Kicker ZX300.1: 300W@2Ohm, 20A+20A fuses on it

Hertz EP4: 4x60W@4Ohm, 25A+25A fuses

Click to read more...

 

[rod_b 10+ year member]

Go here. Somewhere near the middle, there is a System Power Design Assistant that you can enter your amp wattages and it will give you some recommendations on fuses and wire gauge.

 

[BKIII 10+ year member]

easiest way to figure out the right fuse size is:

take the wattage of the amp divided by 12(the amount of volts from your battery)

then round up to the size fuse you need.

 

[DOOM_NX 10+ year member]

rod_b, thanks a lot, that site was really helpful. Now I see that fuses need to match wire gauge. I'm gonna check the numbers later.

BKIII, that way suggests putting a 25A fuse on a 300W amplifier... Something just doesn't fit, i don't know...

 

[shimmyz 10+ year member]

I would go 50 on the Kicker and 60 on the Hertz

 

[DOOM_NX 10+ year member]

Why would you go 60A on the Hertz?

 

[Pioneer~Saturn 5,000+ posts]

What size power wire is a better question...What gauge is it?

 

[GlocksRock 10+ year member]

Fuse for the power wire, not the amp... amps have their own built in fuses

 

[shimmyz 10+ year member]

Why would you go 60A on the Hertz?

If it has 2 25amp fuses like you stated, It is common practice to fuse your block with a slightly bigger fuse. Do you have the manuals for these amps? Some manuals tell you what size fuse to use inline

 

[n2audio 5,000+ posts]

It's not possible to suggest a fuse size w/o knowing the size of the wire. As BCAE1 explains, and Glocks mentioned - that is what fuses are for.

ASSUMING you have 4 ga main and 8 ga secondary I would go no more than 125 up front and 50 at the d-block.

I always suggest fusing as low as possible and still have adequate current to your amps, so I'd go 100A up front, 40 for the Kicker, 50 for the hz. It's just an added measure of protection vs, for example, running 4 ga to your Hertz and using a 125A fuse just because you can -- I'd still make it 50.

Regarding the question about a 25 for the Kicker. They've always under-rated their amps so it will probably perform more like a 400w amp - which explains 40A fuse. However, since current draw of an amp playing music (on an RMS basis) is no where near its maximum possible current draw, AND it typically takes quite a bit more current than what the fuse is rated for to get it to actually open - there is nothing wrong with underfusing - it would just provide a little more protection.

 

[DOOM_NX 10+ year member]

Well, I'm back with wire details.

Battery to distribution block: Audison connection 8AWG with audison fuse holder and a grey audison fuse (dunno what type ANL fuse has grey colour)

He also ran 2 8AWG wires to the amplifiers, Hertz wire fused at 50A and Kicker wire fused at 40A.

I know it's wrong. What is exactly wrong? //content.invisioncic.com/y282845/emoticons/frown.gif.a3531fa0534503350665a1e957861287.gif

 

[dipitydoo 10+ year member]

8 gauge wire from distribution block to amps, those fuses are fine. Assuming battery to distribution block is 4 gauge are larger, you would want ~100amp fuse at the battery.

 

[IDSkoT 5,000+ posts]

If it has 2 25amp fuses like you stated, It is common practice to fuse your block with a slightly bigger fuse. Do you have the manuals for these amps? Some manuals tell you what size fuse to use inline

Well, if you'd search your info first, you'd realize you fuse the wire as per wire gauge / length... it has NOTHING to do with the amps.

And as you see from here: http://www.bcae1.com/wire.htm

A little bit down, it will say the recommended maximum fuse.

And to clear up... the "common practice" of adding up the fuses on your amps and using that to fuse the wire is one, ignorance, and two, for cost reasons. While that wire won't need to run more than X amount of amps, as it's known, amps have internal fuses (most modern ones do). The fuse is just in case there's a power surge, or the amps are trying to pull too many amperes through the wire, it's to cut the connection so that the wire doesn't get too hot and catch on fire.

Wire on fire = car on fire = Bye bye car / audio.

Oh, and OP: You might want to upgrade to 4-AWG power wire from your battery to your distro block. Your amps aren't getting enough power. They're pulling 90 amps, and the most 8 AWG can do is about 50 amps. If you plan on upgrading anytime in the future, save up more and buy 1/0 AWG (Or 0 gauge). This size will be able to power I believe up to about 3,000 RMS.

 

[n2audio 5,000+ posts]

And to clear up... the "common practice" of adding up the fuses on your amps and using that to fuse the wire is one, ignorance, and two, for cost reasons.

Most of that paragraph was confusing so I cut out the main idea, which is confusing in itself. Anyway I THINK I disagree. Using the amp's fuse size is a perfectly acceptable way to size your fuse, but more importantly, your wire.

Oh, and OP: You might want to upgrade to 4-AWG power wire from your battery to your distro block.

Agreed - 90A will definitely require 4 ga.

 

[Mexar 10+ year member]

You fuse to the size of your wire, the inlines / distro fuses are there SOLELY to protect the wire. Your amp's fuse's will take care of the amp itself. The size of the fuse depends on the gauge used AND the heat rating of the wire casing itself.

Now, 8 gauge wire, is rated for 40amps (at 90C casing), so you fuse it for 40, no more.

The ONLY time you can over-fuse a wire, legitimately, is for an electric motor, because these have a higher start-up draw (In the range of 300%) and you don't want to blow a fuse / trip a breaker everytime the motor tries to turn on.

4 gauge, I'd have to look up to set in stone what it's capable of carrying, but 2awg is rated for 105 amps (With a 90C jacket). Going off those, I'd say 80-90amps for the 4 gauge