Inline Fuse Size for Power

[lee]

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

Did not use an inline fuse but ran them through the switches on the dash that are connected to the breakers beside the dash.

[xpjim1]

On my switches did the same as Lee. I replaced the existing switches which were already wired thru a fuse block under the dash.

[Jeff T]

I have two questions (well technically 3 questions):

1-I'm planning to use a 250 amp fuse. Is this too large to be safe? Should I be using 200 amp to be safer?
2-Should I be using fused distribution blocks (0 gauge to 4 gauge) instead of non-fused distribution blocks?

Install is underway. Spent yesterday doing some planning, ran a few wires, and got the box cut into the kick panel.

[Moki]

My plan was to run 4 cable gauge cable up to the front of the boat (about 15 feet) with a fused power distribution block which then goes to 8 gauge to fused amplifiers. Sounds like I need to add a fuse near the battery?

[dogbert]

My plan was to run 4 cable gauge cable up to the front of the boat (about 15 feet) with a fused power distribution block which then goes to 8 gauge to fused amplifiers. Sounds like I need to add a fuse near the battery?

That's what I did on mine, but it's actually right before my battery switch...but same concept.

[spharis]

Moki, IF you choose to fuse the power run before the 4-8 gauge distro block, I would recommend getting a breaker vs. a fuse, as it is much easier to install and maintain. The lug connections are nice for using prebuilt wire.

[philwsailz]

I have two questions (well technically 3 questions):

1-I'm planning to use a 250 amp fuse. Is this too large to be safe? Should I be using 200 amp to be safer?
2-Should I be using fused distribution blocks (0 gauge to 4 gauge) instead of non-fused distribution blocks?

Install is underway. Spent yesterday doing some planning, ran a few wires, and got the box cut into the kick panel.

Good morning Jeff-

250A is fine for your application; we are okay using over-current protection that is rated at a higher value than the load. There are differing schools regarding the relative merits of fuses vs. breakers; I am indifferent personally, and will point out that the breaker has the ability to be reset, saving the cost of a new fuse. That being said, if you choose to go the breaker route, be sure to get a MANUAL reset breaker, (like is shown in Spharis' post) rather than an auto-reset breaker. Auto-reset breakers are bad news; if you end up with a problem that will trip a breaker, the breaker needs to stay tripped until the problem is fixed. Auto-resets will just turn back on, and you can start a fire; maybe more slowly than without over-current protection, but the potential is still there.

The law as it relates to boat manufacturers says that the over-current protection for the load needs to be within 7 inches of the battery. If you have a battery switch, I think it best to put the fuse/breaker AFTER the battery switch, if you intend to, or have the possibility/probability of running the audio system off of more than one battery bank. If you are dedicating a battery bank to the stereo, and leaving another battery available primarily as a starting battery, wire the amp(s) straight to the dedicated stereo battery bank, and do not run it through the batt switch.

For the amps you are using, and if you intend to use a distribution block, there is no need to use a fused distribution block. The primary 250A over-current device back at the battery makes the use of a fused distribution block redundant.

Hey Dogbert: let me point out that if you have fused your power wire BEFORE your batt switch, you run the probability that your starter motor is also pulling current through the fuse you installed for your stereo power wire. If I am reading your post correctly, you might want to re-think this, for two reasons:

If you are running the stereo hard, and attempt to start the motor, you can blow your fuse IF in fact the starter is powered from the batt switch, (and I have to believe it is, if I am reading you correctly). By law. the starter motor is EXEMPT from over-current protection as we are talking about it, and is often provided with its own built-in breaker/relay/fuse dedicated just to the starter motor.

In effect, with the fuse in front of the batt switch, you are ONLY providing over-current protection for your amplifier power wiring when the batt switch is in the position that is connected to the fused power wire leg. When in the other battery position, your amp power wire is not over-current protected.

Good luck Jeff! Have fun too! Let us know how it all turns out!!!!

[dogbert]

Moki, IF you choose to fuse the power run before the 4-8 gauge distro block, I would recommend getting a breaker vs. a fuse, as it is much easier to install and maintain. The lug connections are nice for using prebuilt wire.

Do you know if this is safe to use within the engine compartment? I ask because both Moki and I have our batteries located near the transom but connected to the engine compartment. In other words, when this sucker trips, will it arc or heat up at all?

[Jeff T]

I have two questions (well technically 3 questions):

1-I'm planning to use a 250 amp fuse. Is this too large to be safe? Should I be using 200 amp to be safer?
2-Should I be using fused distribution blocks (0 gauge to 4 gauge) instead of non-fused distribution blocks?

Install is underway. Spent yesterday doing some planning, ran a few wires, and got the box cut into the kick panel.

[philwsailz]

Do you know if this is safe to use within the engine compartment? I ask because both Moki and I have our batteries located near the transom but connected to the engine compartment. In other words, when this sucker trips, will it arc or heat up at all?

Good question!

The major concern, and I know by your post that you understand, is the chance of igniting fuel vapors. A circuit breaker, by nature of its action WILL arc, or spark, if presented with a load that will cause it to trip. To be totally sure, you will want to look for and purchase a breaker that is IGNITION PROTECTED. There is a rating and a specification for this, and most marine breakers will be ignition protected.

In basic principle, a device that is ignition-protected will either be completely sealed in such a manner that no flammable vapors can enter the device, or the device is built so rubustly that the little ignition that is created, if there are flammable vapors present, is completely and totally contained within the device, and cannot ignite vapors outside of the device.

One can assume by construction that a fuse has the POTENTIAL to be ignition protected, but as I type and think, I realize that there is as much a possibility that there are fuses that ARE NOT ignition protected. Hmmm....

This has me thinking about MY installation now....

The best answer, if you want to do your work by the same standards and laws that the boat builders have to go by is to seek out, find, and use a circuit breaker that is certified as ignition protected. That will allow you a high degree of comfort with installation in the engine comnpartment.

I may go do a little research on-line to see if I can find a link and a possible source...

[philwsailz]

check your PM

[spharis]

You can use that breaker in the compartments. It is as safe or safer than the amps in regards to circuit protection.

Also in addition to the fuse/breaker on the starter cable, A starter pulls massive amperage. It will surely blow a fuse eventually.

[Moki]

Moki, IF you choose to fuse the power run before the 4-8 gauge distro block, I would recommend getting a breaker vs. a fuse, as it is much easier to install and maintain. The lug connections are nice for using prebuilt wire.

Dang, I just bought an inline 200 Amp fuse:


I am doing it, however, I am with Spharis on this one, there is no metal along my power run where there is a chance where it could short and as Lee mentioned, Tige runs an unprotected wire up to the helm, where it is fuse protected there. But since it is such a long run, I guess better safe than sorry.

[philwsailz]

Big Breakers

I have not spent a TON of time, but have checked a few places.

I have not yet found an ignition-protected manual-reset circuit breaker that is big enough for Jeff's needs.

Hey Jeff, BTW, still checking on the batt question. I will call...

[dogbert]

Hey Dogbert: let me point out that if you have fused your power wire BEFORE your batt switch, you run the probability that your starter motor is also pulling current through the fuse you installed for your stereo power wire. If I am reading your post correctly, you might want to re-think this, for two reasons:

If you are running the stereo hard, and attempt to start the motor, you can blow your fuse IF in fact the starter is powered from the batt switch, (and I have to believe it is, if I am reading you correctly). By law. the starter motor is EXEMPT from over-current protection as we are talking about it, and is often provided with its own built-in breaker/relay/fuse dedicated just to the starter motor.

In effect, with the fuse in front of the batt switch, you are ONLY providing over-current protection for your amplifier power wiring when the batt switch is in the position that is connected to the fused power wire leg. When in the other battery position, your amp power wire is not over-current protected.

I just wanted to bring this back to life. As I am rewiring my setup, I did verify that my ignition switch turns off the stereo every time I start the engine.
So, I think I am ok.