# Thread: Calculating the correct fuses needed.

1. ## Calculating the correct fuses needed.

I need to know what fuses to use on my wiring.

I have a line coming from the battery with in-line fuseholder, then a fused power distro block and a ground distro block.

This is what will be running off of them:

Opus 150w
400w Amplifier

Here are my guesses if the formula is right:

150w / 12v = 12.5A
400w / 12v = 33.3A

Output of both devices = 45.8A

So I will need to go above that, say maybe a 60A fuse for the inline fuseholder and then a 20 and a 40 for the power / ground distro?

2. the opus should be fused at 15A I would make your amp 35A either way the fuse has to be rated for the cable your using as this is what it is protecting and not the unit itself, they should have their own built in protection. If you run cable to take 100A you can fuse it at 100A it will make no odds to what your running like wise if you run cable for 50A the thats what the fuse has to be.

3. Ok this is confusing me now.

If it helps I am running 4AWG from the battery - what inline fuse should I have there?

From the distro blocks I am running 8/9 AWG to the two devices.

4. ok use a 60A fuse on the fuseholder that is near the battery ( within 18inches ) and then on the disty block use 15A fuse for the carputer and 35A fuse for the amp, and if you cant find those ratings in your fuse type then use the next larger fuse rating `

5. Thankyou

One last question, should the ground block also be fused?

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