Inline Fuse Size for Power

[Jeff T]

I have another question...

Obviously I need to have an inline fuse for my power wire. I'm running 0 gauge to a block, then running 4 gauge to each amp:

zx650.4
zx350.4
zx750.1

How do you figure out what size fuse is needed?

[philwsailz]

I have another question...

Obviously I need to have an inline fuse for my power wire. I'm running 0 gauge to a block, then running 4 gauge to each amp:

zx650.4
zx350.4
zx750.1

How do you figure out what size fuse is needed?

Add up the fused amount for each amp:

zx650.4 = 80A
zx350.4 = 40A
zx750.1 = 80A

200A total for all three amps.

The U.S. Coast Guard and the ABYC will allow over-current protection up to 1.5 times the circuit draw, as long as the power wire's insulation has the heat resistacne to do so, (200C or 392 deg. F for this case, assuming 300A) but 300A is probably overkill in this instance. You want over-current protection somewhere between 200 - 250 amps, in my opinion, and to comply with the laws that the boat builders have to go by.

Typical car stereo thinking is that the fuse/breaker be within 18" of the battery, but the Cost Guard says 7".

Good luck and go for it!

[Jeff T]

how do you figure the fused amount for each amp?

[philwsailz]

how do you figure the fused amount for each amp?

You can go to each amp and add up the indivividual fuses that are on the amp, or go to the owners' manuals. The manauls have the total fuse protection for each amp in the instructions.

[Jeff T]

Did you just happen to know the fused protection for each of the amps I listed, or did you look it up?

[philwsailz]

Did you just happen to know the fused protection for each of the amps I listed, or did you look it up?

Looked it up... It is available at the Kicker website. www.kicker.com
SUPPORT
TECH SUPPORT
MANUALS

From there you can navigate to the .pdf you need for any of the amps

[spharis]

I don't run wire fusing over short runs in marine applications. No point being there is no chassis ground.

[philwsailz]

I don't run wire fusing over short runs in marine applications. No point being there is no chassis ground.

Hey spharis-

First, let's call this a spirited discussion, rather than an argument, okay?

Let me point out that any electrical component, or any mechanical component that is bonded to the engine block or connected to the battery is a potential source of ground. Were you to have a power wire rub and chafe through the insulation at a point where it could contact any of the above points and make contact with something that is electrically at the electrical ground plane, you will create a spark.

I have attached a link to the U.S.C.G. Boat builder's handbook:
http://www.uscgboating.org/safety/bo.../downloads.htm

Download subpart I, Electrical Systems, and take a look.

On the top of page 63, you will find the Federal Law, (Title 33CFR section 183.455) as it applies to boat builders, that states that over-current protection is required for each ungrounded current-carrying conductor.

ABYC Guideline E-11, (I think that is the one) says the exact same thing, and is the standard by which the NMMA certifies every Tige' boat.

[spharis]

Were you to have a power wire rub and chafe through the insulation at a point where it could contact any of the above points and make contact with something that is electrically at the electrical ground plane, you will create a spark.

And where would that happen on a run of 1.5 feet from a battery to an amp, that it wouldn't happen on the 7" before the fuse. Notice I said on short runs. There's no more chance of that happening than of my main starter power lead doing so down in the bilge. It isn't protected anywhere. Even IF a wire did chaffe, there's nothing for it to ground to.....no metal chassis, no firewall passthrough. Most wiring in a boat is protected by those little thermal breakers at the dash, way over the 7". What about the 12 feet of wire before that that connects at the power distro point back at the engine, or near the battery?

I have attached a link to the U.S.C.G. Boat builder's handbook:
http://www.uscgboating.org/safety/bo.../downloads.htm

Download subpart I, Electrical Systems, and take a look.

On the top of page 63, you will find the Federal Law, (Title 33CFR section 183.455) as it applies to boat builders, that states that over-current protection is required for each ungrounded current-carrying conductor.

I am not a manufacturer with the responsibility of building a boat for the public. Unprotected, ungrounded current carrying conductor of over 3 feet would refer to absolutely nothing in my boat except the starter, and the ignition.

[Jeff T]

I don't run wire fusing over short runs in marine applications. No point being there is no chassis ground.

SPH, what do you consider long? I'm thinking that my power runs could be as long as 15ft.

EDIT:
Nevermind.

[philwsailz]

You might be fine in your situation! I still would personally recommend against it.

'Just want to point that there are a LOT of sources for electrical ground on a boat. a power wire popping loose while going over another boat's wake and landing against the amp chassis is one that immediately comes to mind...

I just know the last time someone got their wrench between power and ground that they might have wished it was over-current protected. Wrenches get hot quick! (yeah, they should have disconnected ground at the battery before wrenching on the darned thing!)

[spharis]

If your amp has internal fusing, then I would run without a line fuse up to about 4 feet in a boat. in an auto, I take the method of always fusing to the components, and not the conductor size, regardless of the length of the wire.

For things like automatic bilge pump, or fat sac bags, no fuses.....I am not even sure Tige' adds those right now.

If I am not mistaken, the pumps Lee had installed pics on don't go through any protection either.

Do I plan on adding a fused distro block?....yes
Is it high on the priority list?.....not really....probably will not get to it for another few months.

[philwsailz]

There's no more chance of that happening than of my main starter power lead doing so down in the bilge. It isn't protected anywhere.

This is fun!

Same download document in U.S.C.G. Subpart I, page 66

See figure 24-d CRANKING MOTOR POWER SUPPLY CONDUCTORS
"battery cable to cranking motor is exempt"

As for the wiring going to the breaker/fuse distro panel at the helm, it should be overcurrent protected in some manner and probably is. If not, well...

Hey, sorry, man, I hope you are having as much fun as me with this. I am just trying to help, and I am just bringing awareness up to the level that the builders have to adhere to. As individual owners, we are free to make our own decisions.

[THE g]

When fusing any car audio I have always used the largest fuse for the wire gauge,this way the voltage drop through the fuse is as little as possible.
I feel this is the best way to me?

[spharis]

When fusing any car audio I have always used the largest fuse for the wire gauge,this way the voltage drop through the fuse is as little as possible.
I feel this is the best way to me?

That is an acceptable method for high amperage systems. I do not do it that way, but many do.