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Fuse for sound system 

 

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 Post subject: Fuse for sound system
Posted: Thu May 21, 2009 11:52 am 
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G'day Everyone
I'm installing an aftermarket sound system into my XR6.

4 Speakers 55W RMS @ 4ohm
1 Sub - 500W RMS @ 4ohm
Head Unit
2 amps
1 4ch RMS 50Wx4 @ 4ohm, total Max 400W
1 Mono Block RMS 460W @ 4ohm , Max 850W


now I have a wiring kit with a fuse, but I'm not sure whether the fuse is the correct fuse to use.
I mean I dont know if the amperage on the fuse is correct.

So my question is what is the correct amperage for the fuse that i should be using?

Thanks Peter
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 Post subject: Re: Fuse for sound system
Posted: Thu May 21, 2009 12:18 pm 
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Ok
I think I may have figured it out

Power(P) = Amp(I) x Voltage(V)
I = P/V

Total power of my system, i.e of the amplifiers is 850W(mono Block) + 400W(4ch) = 1250W

Voltage that the car puts out when running is 14V

therefore

I = 1250W/14V

I = 90 amps

therefore i need a 90amp fuse for the power cable.

Is this correct? can anyone clarify this for me?

Thanks Peter
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 Post subject: Re: Fuse for sound system
Posted: Fri May 22, 2009 6:18 pm 
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Yeah you've got the calculation right.

Also, you can add the values of the fuses in your amps to get an approximation.
Most amps have a fuse in the end.
Don't be surprised if you get a bit of a discrepancy between what you worked out and adding the 2 amp fuses together.
Depending on your brand you might find the power figures they promote are a little 'flexible'.

 

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 Post subject: Re: Fuse for sound system
Posted: Fri May 22, 2009 8:03 pm 
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Sweet
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 Post subject: Re: Fuse for sound system
Posted: Fri May 22, 2009 10:24 pm 
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i was gonna say the same thing, just add the fuses up in the amps and match that with a fuse, one of my amps has 2 40amp fuses and the other has 2 30amp fuses so i have 100amp in the front of the car, the thing will never pull that many amps, i only have the amps on about half or less and the the headnit do the work so the amps dont work as hard plus the amps i have give me plenty of headroom anyway(meaning they have more power than i need so the dont have a hard time pumping out the tunes

 

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 Post subject: Re: Fuse for sound system
Posted: Sat May 23, 2009 2:41 pm 
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As sikford said all thats need is to add the fuse rating of what your amps should already have and base the main fuse value off those values totalled.

Amplifier efficiency does come into play but this actually works in your favour when using the maximum rated fuse.

Just ensure you try to keep the main fuse as close to the battery or power source as possible....leaving a bit of extra cable incase you need to re-terminate in future etc.

 

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 Post subject: Re: Fuse for sound system
Posted: Sat May 23, 2009 10:45 pm 
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sweet thanks guys, will thake this into consideration

Cheers

Peter
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 Post subject: Re: Fuse for sound system
Posted: Thu May 28, 2009 11:35 pm 
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something else to consider is that the fuse at the battery isnt to protect the equipment, its to protect your car in case the insulation on the cable rubs through and shorts out to the car body, so you need to use a fuse appropriate to your cable size, ie: 4ga needs to be fused at a maximum of ~120 amps, etc
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 Post subject: Re: Fuse for sound system
Posted: Fri May 29, 2009 12:15 am 
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MoffatGhia wrote:
something else to consider is that the fuse at the battery isnt to protect the equipment, its to protect your car in case the insulation on the cable rubs through and shorts out to the car body, so you need to use a fuse appropriate to your cable size, ie: 4ga needs to be fused at a maximum of ~120 amps, etc


agreed 100%


the fuse that comes from you battery should be as close as it can because anything before the fuse is unprotected the fuses on the amps will look after themselfs

 

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